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  • ASTRONOMY
  • 1985-1989  (219)
  • 1980-1984
  • 1975-1979
  • 1987  (219)
  • 1
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    Palomar-Leiden minor planets - Proper elements, frequency distributions, belt boundaries, and family memberships (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Tabulations are presented for the proper elements of 1227 higher accuracy orbits of faint minor planets encompassing earth and deep Mars crossers, Trojans, and Hildas. The distribution of the closest approach distance to Mars drops off sharply near zero, while that for Jupiter vanishes near 1.1 AU; it is suggested that Mars and Jupiter have caused these boundaries, so that the asteroid belt must have been larger early in the solar system's history. Some 3.5 percent of the sample, primarily shallow crossers, can impact Mars; the fortuitous alignments required for impact occur with near-simultaneity for these objects, so that they will episodically bombard Mars.
    Schlagwort(e): ASTRONOMY
    Materialart: Icarus (ISSN 0019-1035); 72; 276-303
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  • 2
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    Ground-based infrared observations of variable IRAS sources as candidates for late asymptotic giant branch stars (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Analysis of the color distribution of OH/IR stars and IRAS low-resolution spectra class 30 objects suggests the presence of a well-defined evolutionary sequence which is populated by late asymptotic giant branch (LAGB) stars. The paper reports ground-based identification and infrared photometry of 10 candidates of news LAGB stars. None of the selected sources are found to have optical counterparts, and eight of the 10 show a strong 10-micron silicate absorption feature. It is suggested that these stars represent an invisible extension of extreme Mira variables and are some of the most evolved stars observed to date.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 321; 975-983
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  • 3
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    Fourier removal of stripe artifacts in IRAS images (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: By working in the Fourier plane, approximate removal of stripe artifacts in IRAS images can be effected. The image of interest is smoothed and subtracted from the original, giving the high-spatial-frequency part. This 'filtered' image is then clipped to remove point sources and then Fourier transformed. Subtracting the Fourier components contributing to the stripes in this image from the Fourier transform of the original and transforming back to the image plane yields substantial removal of the stripes.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Journal (ISSN 0004-6256); 94; 1092-109
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  • 4
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    Identification of a constellation from a position (1987)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A table is presented which permits rapid determination of the constellation in which an object is located from its 1875.0 position. Directions for accessing and using the table are given. The historical background to the table's development is briefly stated.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 99
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  • 5
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    Radar astrometry of near-earth asteroids (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: An uncertainty analysis is conducted for four asteroids with different optical and radar observation histories in order to ascertain the degree to which near-earth asteroid ephemerides can be improved by means of radar observations. For any given set of optical and radar observations and their associated errors, the angular and earth-asteroid distance uncertainties are calculated as functions of time through 2001. The radar data furnished only a small absolute improvement in such cases as that of 1627 Ivar, where a long history of optical astrometric data exists, but dramatic reductions in ephemeris uncertainties are obtainable for asteroids having only short optical data histories.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Journal (ISSN 0004-6256); 94; 189-200
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  • 6
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    The multichannel astrometric photometer and atmospheric limitations in the measurement of relative positions (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The operational Multichannel Astrometric Photometer (MAP) now in use in the Allegheny Observatory astrometric program is the culmination of a decade of design and development effort. A detailed description of the system and its related software is followed by analysis of data acquired in four stellar regions. The study indicates an accuracy (in the sense of conformity to the best model), per night, for stars of the eighth magnitude or brighter, of 0.003 arcsec or better. These data points each have approximately twice the precision of the annual normal points obtained in our photographic program. Accuracy is shown to depend on: (1) the photon-count rate of the target star (it follows that the number of photons from the reference frame is also in important factor), (2) the duration of the observation, (3) the angular size of the reference frame, and (4) the quality of the astronomical seeing. Since (4) and, to a lesser extent, (1) involve the atmospheric characteristics at the time of observation, the probable performance at more favorable sites is discussed briefly.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Journal (ISSN 0004-6256); 94; 213-224
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  • 7
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    GUST86 - An analytical ephemeris of the Uranian satellites (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The General Uranus Satellite Theory GUST (Laskar, 1986) is used for the construction of an analytical ephemeris for the Uranian satellites. The theory is fitted against earth-based observations from 1911 to 1986, and all radio and optical data obtained during Voyager encounter with Uranus. Earth-based observations alone allow the determination of masses which are within 15 percent of the values determined by the Uranus flyby. The analysis of all the observations confirm the values of the masses obtained during the encounter (Stone and Miner, 1986) and give a complete set of dynamical parameters for the analytical theory. An analytical ephemeris, GUST86, with an estimated precision of about 100 km with respect to Uranus is obtained.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 188; 1, De
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  • 8
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    All-sky monitors for X-ray astronomy (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The rationale for a semipermanent all-sky X-ray monitor and a variety of options for its implementation are discussed. It is concluded that the Space Station offers an excellent opportunity for hosting such a monitor, and that a set of pinhole cameras can be configured to provide an effective and economical monitor system. A baseline of six independent pinhole modules, each of which requires approximately 1 cu ft, 30 pounds, 2 W and 100 bits per second, can provide full sky coverage with scientifically interesting sensitivities. No other resources or special accommodation (such as detailed alignment registration, time-tagging, or on-orbit servicing) would be required. The baseline system can locate bright sources to a few arcmin and can simultaneously measure each of the several hundred sources in the sky brighter than a few thousandths the intensity of the Crab nebula every day for decades.
    Schlagwort(e): ASTRONOMY
    Materialart: Space Science Reviews (ISSN 0038-6308); 45; 3-4,
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  • 9
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    The MIT spectroscopy investigations on AXAF and the study of supernova remnants (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The MIT High Resolution X-Ray Spectroscopy experiment on the AXAF, which will study physical conditions in celestial sources by means of detailed measurements of emission and absorption features in their spectra, involves two complementary dispersive instruments: Bragg Crystal Spectrometer (BCS) and High Energy Transmission Grating (HETG). This paper discusses the principles of operation of BCS and HETG and the results that will be obtained by these instruments. Measurements of individual line strengths obtained by the AXAF spectrometers will allow the application of plasma diagnostic techniques to a study of the detailed physical conditions in celestial objects, particularly in the optically thin plasma of supernova remnants, which is particularly well suited to the application of plasma diagnostics.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Letters and Communications (ISSN 0888-6512); 26; 1-2,
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  • 10
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    The advanced X-ray astrophysics facility - An overview (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: This paper presents an overview of NASA's Advanced X-Ray Astrophysics Facility (AXAF), which is planned for launch in the 1990s and is expected to operate in space for at least 15 years. The design of the X-ray telescope is discussed and the instruments that may fly at the start of the AXAF mission, the principal investigator of each instrument, and the instrument performance parameters are listed. The AXAF instruments will include low-energy and high-energy transimission gratings, a Bragg crystal spectrometer, CCD imagers, an X-ray calorimeter, and a microchannel plate imager. The long lifetime of the AXAF will make it possible to follow up on the HEAO-2/Einstein results, the more recent X-ray observations performed by European and Japanese satellites, and the future ROSAT all-sky survey. The long lifetime of the AXAF, together with the servicing capability that will be offered by the Space Station, will also provide the opportunity of incorporating other instruments into the observatory.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Letters and Communications (ISSN 0888-6512); 26; 1-2,
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  • 11
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    Plasma structures in comets P/Halley and Giacobini-Zinner (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: An overview of large-scale plasma phenomena is presented based on results of spacecraft probing of comets Halley and Giacobini-Zinner and on worldwide submissions to the Large-Scale Phenomena Discipline Specialist Team of the International Halley Watch. Examples of tail phenomena and science are presented with emphasis on observed disconnection events. The archive of this material will clearly be very valuable for studying the comet/solar-wind interaction during the 1985-1986 apparition of Halley's comet.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 187; 1-2,
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  • 12
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    IRAS known asteroid prediction and association (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Techniques and procedures employed to obtain data concerning the known asteroids from IRAS observations are discussed. The IRAS observations covered 95 percent of the sky with at least four scans of the telescope field of view. A search was first carried out for geometrical intersections of the trajectories of a given asteroid and the telescope boresight, following which a matched sighting was sought for each such intersection among the actual IRAS point source detections. By using ground based measurements of visual magnitudes, IRAS observations of IR brightness, and a thermal model, albedos and diameters have been computed for 1,822 known asteroids, increasing the amount of this kind of information by about an order of magnitude.
    Schlagwort(e): ASTRONOMY
    Materialart: Journal of the Astronautical Sciences (ISSN 0021-9142); 35; 287-299
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  • 13
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    On the simple models for the interpretation of centimeter-wavelength radio observations of asteroids (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The predictions of the two-layer models used to interpret radio spectra of the asteroids have been examined. It is clear that one must treat the models with caution as the physics is highly simplifed. Although the predictions are in accord with physical expectations, careful attention to the circumstances of the observations is essential. The lack of short-centimeter wavelength measurements of dielectric properties is especially vexing. Some simple improvements to the models based on studies of the lunar radio emission by Keihm and using radar measurements of asteroid surface characteristics by Ostro and colleagues are suggested. Even so, the calculation of a realistic continuum-emission spectrum for asteroidal bodies from 20 cm wavelength to 20 microns wavelength remains a formidable task.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 99; 1009-101
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  • 14
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    Observation by Pioneer 7 of He(+) in the distant coma of Halley's comet (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Plasma analyzer data obtained by Pioneer 7 during its approach to about 12.1 million km from the nucleus of Comet P/Halley are presently interpreted as He(+) generated by charge exchange of the solar wind He(2+) with neutral cometary material. The maximum He(+) flux was detected several hours after the closest March 20, 1986 approach of the spacecraft, and is noted to be not only larger than expected, but also to exhibit large, discontinuous flux changes.
    Schlagwort(e): ASTRONOMY
    Materialart: Icarus (ISSN 0019-1035); 71; 192-197
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  • 15
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    The feasibility of periodicity searches in gamma-ray astronomy (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: It is presently noted that, in some cases, the usually infeasible conduct of searches in gamma-ray astronomy can be rendered feasible by means of a time-smoothing technique that yields only a moderate sensitivity loss. The total observing time is subdivided into a convenient number m of subintervals, and summing the values of H of each of the subintervals. This will reduce the number of independent frequency values by a factor m due to the shorter observing time.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 175; 1-2,; 353
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  • 16
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    A Palomar Observatory Sky Survey atlas of selected molecular clouds (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Forty-three cold, dense molecular clouds are digitized from the Palomar Observatory Sky Survey glass plates and presented with epoch 1950.0 equatorial coordinates. Regardless of the cloud's extent, the digitized area is limited to a 23 arcmin square on the sky with pixel size of about 1.3 arcsec. The optical maps presented herein are useful for comparing complementary molecular cloud maps from radio or infrared instruments and can be obtained in FITS format for use on astronomical image-processing systems.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Journal Supplement Series (ISSN 0067-0049); 64; 127-129
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  • 17
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    Orbits of the ten small satellites of Uranus (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Orbital elements are presented for the ten small satellites discovered by Voyager 2 at Uranus. These ten new satellites, whose provisional IAU designations are 1985UI and 1986UI through 1986U9, lie for the most part in equatorial, circular orbits; the most notable exception is 1986U8, the outer epsilon-ring shepherd, whose eccentricity e = 0.0101. Unlike the Voyager discoveries at Saturn, which included two co-orbiting satellites and three librators, the ten small Uranian satellites all have quite different semimajor axes.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Journal (ISSN 0004-6256); 93; 1268-127
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  • 18
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    IRAS surface brightness maps of reflection nebulae in the Pleiades (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Surface brightness maps at 12, 25, 60, and 100 microns were made of a 2.5 deg x 2.5 deg area of the reflection nebulae in the Pleiades by coadding IRAS scans of this region. Emission is seen surrounding 17 Tau, 20 Tau, 23 Tau, and 25 Tau in all four bands, coextensive with the visible reflection nebulosity, and extending as far as 30 arcminutes from the illuminating stars. The infrared energy distributions of the nebulae peak in the 100 micron band, but up to 40 percent of the total infrared power lies in the 12 and 25 micron bands. The brightness of the 12 and 25 micron emission and the absence of temperature gradients at these wavelengths are inconsistent with the predictions of equilibrium thermal emission models. The emission at these wavelengths appears to be the result of micron nonequilibrium emission from very small grains, or from molecules consisting of 10-100 carbon atoms, which have been excited by ultraviolet radiation from the illuminating stars.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 313; 853-858
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  • 19
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    The IHW island network (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Early astronomical photography of comets at perihelion encouraged the establishment of an International Halley Watch (IHW) Team for regularly photographing the Comet. The February 1986 period was particularly troublesome due to the limitations of cometary visibility in the Southern Hemisphere. Schmidt cameras were placed on Tahiti, Easter Island, Faraday Station on the Antarctic Peninsula, Reunion Island and in South Africa. Blue- and red-filter B/W images were obtained every night and color prints were occasionally shot. Each night's images were examined before the next night's photography. Several interesting anecdotes are recounted from shipping, manning and operation of the telescopes.
    Schlagwort(e): ASTRONOMY
    Materialart: Sky and Telescope (ISSN 0037-6604); 73; 258-263
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  • 20
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    Techniques for the analysis of data from coded-mask X-ray telescopes (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Several techniques useful in the analysis of data from coded-mask telescopes are presented. Methods of handling changes in the instrument pointing direction are reviewed and ways of using FFT techniques to do the deconvolution considered. Emphasis is on techniques for optimally-coded systems, but it is shown that the range of systems included in this class can be extended through the new concept of 'partial cycle averaging'.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysics and Space Science (ISSN 0004-640X); 136; 2, Au; 337-349
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  • 21
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    X-ray intensity and spectral variations in the BL Lac sources H2155-304 and PKS0548-322 (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The results from the X-ray observations of two BL Lacertae objects, H2155-304 and PKS0548-322, are presented. The observations were carried out with the HEAO-1 A2 Low Energy Detectors, the High Resolution Imager, and the Monitor Proportional Counter aboard the Einstein Observatory. Correlated X-ray intensity variations of about 20 percent in the 0.15-3.5 keV energy band and about 40 percent in the 1.5-10 keV energy band are observed in H2155-304 over a period of about 8 hr. A factor of two change in the intensity of PKS0548-322 in the 3.5-10 keV energy interval is also detected over a time interval of 1 hr. Variations in the X-ray intensity over a timescale of months and the hardening of the spectrum with increasing intensity are seen in the HEAO-1 A2 data on H2155-304. The shortest observed timescale for the variability is used to derive an upper limit on the mass of the central accreting source in the two BL Lac objects studied here.
    Schlagwort(e): ASTRONOMY
    Materialart: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 227; 525-534
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  • 22
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    Maintaining an expert system for the Hubble Space Telescope ground support (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The transformation portion of the Hubble Space Telescope (HST) Proposal Entry Processor System converts astronomer-oriented description of a scientific observing program into a detailed description of the parameters needed for planning and scheduling. The transformation system is one of a very few rulebased expert systems that has ever entered an operational phase. The day to day operations of the system and its rulebase are no longer the responsibility of the original developer. As a result, software engineering properties of the rulebased approach become more important. Maintenance issues associated with the coupling of rules within a rulebased system are discussed and a method is offered for partitioning a rulebase so that the amount of knowledge needed to modify the rulebase is minimized. This method is also used to develop a measure of the coupling strength of the rulebase.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Goddard Space Flight Center, Proceedings of 1987 Goddard Conference on Space Applications of Artificial Intelligence (AI) and Robotics; p 1-1
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  • 23
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    Optical electronics for meteor observations (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Spectral observations of meteors have been carried out for several years using an optical electronics facility. Interest has centered on faint meteors and their trails in the period of intensive meteor showers. Over 800 meteors were registered during the observation period, with spectrograms obtained for 170 of these. A total of 86 meteors were photographed from two sites and for 25 of these spectrograms of the meteors as well as their trails were obtained. All meteors have undergone routine processing in order to determine atmospheric characteristics. Results are discussed.
    Schlagwort(e): ASTRONOMY
    Materialart: International Council of Scientific Unions, Middle Atmosphere Program. Handbook for MAP, Volume 25; p 410-415
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  • 24
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    Imaging interferometry with non-redundant arrays (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The performance of a set of nonredundant arrays, that convert an existing telescope to an interferometer, was simulated. Each array is a perforated mask, placed at an image of the objective. Each pair of holes in a mask transmits a unique spatial frequency that is present in the target; hence the term nonredundant. Each mask produces a fringe I(f) in the focal plane that is the product of the Fourier transforms of the object and the optical transfer function S(f).
    Schlagwort(e): ASTRONOMY
    Materialart: NASA-Goddard Space Flight Center, Theoretical Problems in High Resolution Solar Physics, 2; p 143-144
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  • 25
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    Spectroscopy and nonthermal processes (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Stellar spectra are analyzed to determine nonthermal processes for cool stars. A shock wave crossing model is supported by a study of the behavior of absorption and emission spectra. The shock waves are attributed to atmospheric kinetics. Circumstellar spectral lines are studied for information about gaseous circumstellar layers. The description of stellar envelopes is carried on through circumstellar dust. Characteristic properties of polarization in the dust are described in the case of specific stars, emphasizing narrowband observations in Mira, semiregular, and supergiant stars. Finally, the direct approach to measuring the angular diameters of stars and mapping the distribution of circumstellar dust and gas by lunar occultation or interferometry is discussed, using two prototype stars, an M supergiant and a dusty carbon star.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington, The M-Type Stars; p 113-207
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  • 26
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    Ultraviolet spectral morphology of the O stars. IV - The OB supergiant sequence (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: An atlas of 25 O3-B8 supergiant spectra in the wavelength ranges 1320-1580 A and 1620-1880 A is presented, based on high-resolution data from the IUE archives. The remarkably detailed relationship between the stellar-wind profiles and the optical spectral classifications throughout this sequence is emphasized. For instance, the (Si IV)/(C IV) ratio reverses between O4 and O6.5; and the B0, B0.5, and B0.7 Ia wind characteristics are each qualitatively unique and distinct from one another. The systematic behavior of nine stellar-wind features with ionization potentials ranging from 114 to 19 eV is summarized as a function of advancing spectral type.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 99; 40-53
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  • 27
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    Infrared-ultraviolet spectra of active galactic nuclei (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Data from IRAS and IUE were combined with ground based optical and infrared spectrophotometry to derive emission line free spectral energy distributions (SEDs) for 29 active galactic nuclei (AGNs) between 0.1 and 100 microns. The IRAS data were scaled down to account for extended emission. These correction factors, determined by comparing small aperture ground based 10.6 micron data with large aperture IRAS 12 micron fluxes, were usually less than 25%. These corrected SEDs are shown.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 727-729
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  • 28
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    Spectrophotometery of Brackett lines in very luminous IRAS galaxies (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Observation of the Brackett-alpha and Brackett-gamma hydrogen recombination lines were made in a sample of galaxies chosen from the IRAS catalog to have high luminosities at infrared wavelengths. Most have strong Brackett line emission indicating large numbers of high mass stars; the formation of these stars may hence be the underlying source for the galaxies' luminosities. However, there are at least two exceptions that may not be explained in this manner: NGC 6240 and Arp 220. Additional evidence indicates that each of these exceptions may be more closely related to Seyfert-type galaxies or other active galactic nuclei.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 701-705
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  • 29
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    A very deep IRAS survey at l(II) = 97 deg, b(II) = +30 deg (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: A deep far-infrared survey is presented using over 1000 scans made of a 4 to 6 sq. deg. field at the north ecliptic pole by the IRAS. Point sources from this survey are up to 100 times fainter than the IRAS point source catalog at 12 and 25 micrometers, and up to 10 times fainter at 60 and 100 micrometers. The 12 and 25 micrometer maps are instrumental noise-limited, and the 60 and 100 micrometer maps are confusion noise-limited. The majority of the 12 micrometer point sources are stars within the Milky Way. The 25 micrometer sources are composed almost equally of stars and galaxies. About 80% of the 60 micrometer sources correspond to galaxies on Palomar Observatory Sky Survey (POSS) enlargements. The remaining 20% are probably galaxies below the POSS detection limit. The differential source counts are presented and compared with what is predicted by the Bahcall and Soneira Standard Galaxy Model using the B-V-12 micrometer colors of stars without circumstellar dust shells given by Waters, Cote and Aumann. The 60 micrometer source counts are inconsistent with those predicted for a uniformly distributed, nonevolving universe. The implications are briefly discussed.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 547-552
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  • 30
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    The initial mass function in HII galaxies (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Observation of a large sample of HII galaxies shows that the emission line ratios of the youngest objects change systematically with gaseous oxygen abundance, which was interpreted as resulting from changes in the initial mass function (IMF) of the ionizing cluster. Comparison with cluster/nebula models shows that both the slope and the upper mass limit of the cluster IMF vary with abundance. In HII galaxies with oxygen abundance about 1/10 that of Orion, the IMF for massive stars must have a slope which is about a factor of 2 smaller than in the Solar Neighborhood.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 479-482
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  • 31
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    Extragalactic infrared spectroscopy (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: The spectra of galaxies in the near infrared atmospheric transmission windows are explored. Emission lines were detected due to molecular hydrogen, atomic hydrogen recombination lines, a line attributed to FEII, and a broad CO absorption feature. Lines due to H2 and FEII are especially strong in interacting and merging galaxies, but they were also detected in Seyferts and normal spirals. These lines appear to be shock excited. Multi-aperture measurements show that they emanate from regions as large as 15 kpc. It is argued that starbursts provide the most plausible and consistent model for the excitation of these lines, but the changes of relative line intensity of various species with aperture suggest that other excitation mechanisms are also operating in the outer regions of these galaxies.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 421-433
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  • 32
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    CO observations of galaxies with the Nobeyama 45-M telescope (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: High-resolution (15 inch), filled aperture maps of the CO (J = 1-0) line emission were obtained for several nearby, CO-bright galaxies like M82, M83, IC342, and NGC891 in order to study star forming activity in these galaxies.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 179-196
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  • 33
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    A correlation between the IRAS infrared cirrus at 60 or 100 microns and neutral atomic hydrogen in the outer galaxy (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: A linear correlation was found between the infrared cirrus at 100 or 60 microns and neutral atomic hydrogen near the galactic plane. Infrared Astronomy Satellite (IRAS) Sky Brightness images were compared to the 0.5 deg resolution Weaver-Williams HI survey in two regions of the outer Galaxy near l = 125 deg and l = 215 deg. The dust temperature inferred is nearly uniform and in reasonable agreement with theoretical predictions of thermal dust emission.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 103-105
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  • 34
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    The Arp Ring: Galactic or extragalactic? (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: The Arp Ring is a faint, loop-like structure around the northern end of M81 which becomes apparent only on deep optical photographs of the galaxy. The nature of the Ring and its proximity to M81 are uncertain. Is it simply foreground structure, part of this galaxy, or is it within the M81 system? Infrared Astronomy Satellite (IRAS) maps of the region show a far-infrared counterpart of the Ring. The infrared data are compared with previous optical and radio observations to try to ascertain its physical nature. The poor correlation found between the common infrared/optical structure and the distribution of extragalactic neutral hydrogen, and the fact that its infrared properties are indistinguishable from those of nearby galactic cirrus, imply that the Arp Ring is simply a ring structure in the galactic cirrus.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 107-110
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  • 35
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    Erratum: IRAS observations of irregular galaxies (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: In Infrared Astronomy Satellite (IRAS) observations of irregular galaxies, galactic blue luminosities were based on standard optical definitions. The blue luminosities (L sub B) were derived from the blue absolute magnitude (M sub B) or form the in band flux. However, the L sub B system for spiral galaxies was based on quasi-bolometric (rather than in band) fluxes. The formulation and resulting statements are corrected.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 257
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  • 36
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    IRAS observations of irregular galaxies (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Normal irregular galaxies seem to be unusual in having vigorous star formation yet lacking the many dark nebulae typical of spirals. The Infrared Astronomy Satellite (IRAS) observations of a large sample of irregulars are used to explore the dust contents of these galaxies. Compared to normal spirals, the irregulars generally have higher L sub IR/L sub B ratios, warmer f(100)/f(60) dust color temperatures, and lower globally-averaged dust/gas ratios. The relationship between the infrared data and various global optical properties of the galaxies is discussed.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 253-256
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  • 37
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    Stellar bars and the spatial distribution of infrared luminosity (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Ground-based 10 micron observations of the central region of over 100 infrared luminous galaxies are presented. A first order estimate of the spatial distribution of infrared emission in galaxies is obtained through a combination of ground-based and Infrared Astronomy Satellite (IRAS) data. The galaxies are nearby and primarily noninteracting, permitting an unbiased investigation of correlations with Hubble type. Approximately 40% of the early-type barred galaxies in this sample are associated with enhanced luminosity in the central (approximately 1 kpc diameter) region. The underlying luminosity source is attributed to both Seyfert and star formation activity. Late-type spirals are different in that the spatial distribution of infrared emission and the infrared luminoisty are not strongly dependent on barred morphology.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 219-226
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  • 38
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    IRAS observations of the Pleiades (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The Infrared Astronomy Satellite (IRAS) observations of the Pleiades region are reported. The data show large flux densities at 12 and 25 microns, extended over the optical nebulosity. This strong excess emission, implying temperatures of a few hundred degrees Kelvin, indicates a population of very small grains in the Pleiades. It is suggested that these grains are similar to the small grains needed to explain the surface brightness measurements made in the ultraviolet.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 117-121
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  • 39
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    Infrared properties of dust grains derived from IRAS observations (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The analysis of several diffuse interstellar clouds observed by the Infrared Astronomy Satellite (IRAS) is presented. The 60/100 micron flux ratios appear to be nearly constant in clouds with up to 1 sup m visual extinction at the center. Observations of a highly regular cloud in Chamaeleon show that the 12/100 micron ratio peaks at an intermediate radial distance and declines towards the center of the cloud. These observations indicate that nonequilibrium emission accounts only for the 12 and 25 micron bands; strong emission observed at the 60 micron band is probably due to equilibrium thermal radiation. The correlation of the 12 micron emission with a red excess observed for a high latitude cloud, L1780, is shown to be consistent with the assumption that both features are due to fluorescence by the same molecular species.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 113-116
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  • 40
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    On the redistribution of OB star luminosity and the warming of nearby molecular clouds (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Infrared Astronomy Satellite (IRAS) observations of the neighborhoods of six outer-Galaxy HII regions were combined with CO observations to show that most of the far infrared (FIR) luminosity from within approximately 25 to 75 pc of the ionizing stars is contributed by dust in molecular clouds, not by dust in the low-density ionized gas. Dust associated with the clouds is warmed by absorption of UV and visible light from the cluster of stars responsible for the ionization. Most of the OB cluster starlight is not absorbed locally. A fraction of the order of 10% of the OB cluster luminosity is absorbed by nearby molecular clouds and reradiated as FIR light. The luminosity per unit mass for the heated clouds is approximately 3 to 13 solar luminosity/solar mass, approximately one order of magnitude greater than the corresponding ratio for clouds found near clusters without O stars, and two orders of magnitude greater than the ratio for dark clouds heated primarily by the interstellar radiation field. If the observations of clouds near outer-Galaxy HII regions are used to characterize the molecular clouds heated by HII regions in the inner-Galaxy, then at most 30% of the Galaxy's molecular cloud mass is actively engaged in the formation of massive stars at the present time.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 75-78
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  • 41
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    High energy gamma ray astronomy (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: High energy gamma ray astronomy has evolved with the space age. Nonexistent twenty-five years ago, there is now a general sketch of the gamma ray sky which should develop into a detailed picture with the results expected to be forthcoming over the next decade. The galactic plane is the dominant feature of the gamma ray sky, the longitude and latitude distribution being generally correlated with galactic structural features including the spiral arms. Two molecular clouds were already seen. Two of the three strongest gamma ray sources are pulsars. The highly variable X-ray source Cygnus X-3 was seen at one time, but not another in the 100 MeV region, and it was also observed at very high energies. Beyond the Milky Way Galaxy, there is seen a diffuse radiation, whose origin remains uncertain, as well as at least one quasar, 3C 273. Looking to the future, the satellite opportunities for high energy gamma ray astronomy in the near term are the GAMMA-I planned to be launched in late 1987 and the Gamma Ray Observatory, scheduled for launch in 1990. The Gamma Ray Observatory will carry a total of four instruments covering the entire energy range from 30,000 eV to 3 x 10 to the 10th eV with over an order of magnitude increase in sensitivity relative to previous satellite instruments.
    Schlagwort(e): ASTRONOMY
    Materialart: Essays in Space Science; p 227-274
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  • 42
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    Space Infrared Telescope Facility (SIRTF) design and thermal analysis (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The design and performance characteristics of an observatory are compared with those of a storage dewar. The critical design technologies required to increase cryogen dewar lifetime are discussed. In particular, outer shell temperature, vapor cooled shields, multilayer insulation performance, and tank support systems are analyzed to assess their impact on cryogen lifetime for both the observatory and the storage dewar. The cryogen lifetime and cryogen mass loss rate of the Space Infrared Telescope Facility (SIRTF) are compared with that of the Infrared Astronomy Satellite and the Cosmic Background Explorer Satellite. A 0.1 percent mass loss per day of superfluid helium dewar can be designed using current state-of-the-art dewar technology. Space-based liquid hydrogen and liquid oxygen tanks can be designed for a 5-year lifetime.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Lewis Research Center, Cleveland, Ohio. Cryogenic Fluid Management Technology Workshop. Volume 1: Presentation Material and Discussion; p 193-220
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  • 43
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    The radio-far infrared correlation: Spiral and blue compact dwarf galaxies opposed (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The recently established correlation between radio continuum and far infrared emission in galaxies was further investigated by comparing normal spiral and blue compact dwarf galaxies. The puzzling result is that the ratio of radio to far infrared luminosity and its dispersion is the same for both samples, although their ratios of blue to far infrared luminosity, their radio spectral indices and their dust temperatures exhibit markedly different mean values and dispersions. This suggests that the amount of energy radiated in the two regimes is enhanced in the same way although the mechanisms responsible for the two components are rather different and complex. The fact that the blue light does not increase at the same proportion shows that both the radio and the far infrared emission are connected with the recent star formation history.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 583-588
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  • 44
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    Radio and infrared observations of (almost) one hundred non-Seyfert Markarian galaxies (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: The 13 cm flux densities of 96 non-Seyfert Markarian galaxies were measured at Arecibo Observatory. Far infrared flux densities have been published for 78 of these galaxies in the IRAS catalog. The radio, infrared, and optical fluxes of these galaxies and of a magnitude limited sample of normal galaxies were compared to clarify the nature of the radio emission in Markarian galaxies. It was found that Markarian galaxies of a given apparent magnitude and Hubble type generally have radio fluxes several times higher that the fluxes typical of normal galaxies of the same magnitude and type. Remarkably, the ratio of radio flux to far infrared flux is nearly the same for most of these starburst galaxies and for normal spiral disks. However, the compact and peculiar Markarian galaxies consistently have about 60% more radio flux per unit infrared flux than the other Markarian galaxies and the normal spirals. It is not clear whether this difference reflects a difference in the evolution of the starbursts in these galaxies or whether there is excess radio emission of nonstellar origin.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 579-582
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  • 45
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    The infrared morphology of galactic centers (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Initial results are presented of a program to map the centers of galaxies in the mid-infrared using the NASA-MSFC 20 pixel bolometer array. Maps at 10.8 micrometer of the galaxies NGC 5236 (M82), NGC 1808, NGC 4536, and NGC 4527 reveal complex emitting regions ranging in size from 500 pc to 2 kpc. The infrared spatial distributions generally resemble those in the visible and radio. In all cases a large fraction of the IRAS 12 micrometer flux originates in spatial structures prominent in the maps.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 497-500
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  • 46
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    The azimuthal and radial distributions of HI and H2 in NGC 6946 (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: A study was completed of the atomic and molecular components of the ISM in NGC 6946. The distribution of molecular clouds was determined from a fully sampled CO map of the inner disk using the 14-meter telescope of the FCRAO. The distribution of atomic gas was derived from VLA observations at 40" resolution in the D configuration. When comparing the global CO and HI properties with other components of the galaxy, it was found that the azimuthally averaged radial distributions of CO, H-alpha, radio continuum and blue light all exhibit similar roughly exponential falloffs, while the azimuthally averaged HI surface densities vary by only a factor of 2 out to R = 16 kpc. This indicates that while the H-alpha/CO ratio is approximately constant with radius, the CO/HI ratio decreases by a factor of 30 from the center of the galaxy to R = 10 kpc.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 491-495
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  • 47
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    VLA continuum observations of barred spiral galaxies (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Observations of NGC 613, NGC 1300, NGC 4314 and NGC 5383 using the VLA at frequencies of 1464.9 and 4885.1 MHz are reported. These objects are a subset of galaxies from which radio emission were searched. The selection criteria were: (1) they are barred spiral galaxies preferentially with different Hubble type; (2) they have a peculiar or hot spot nucleus; (3) they have been observed at far infrared wavelengths by IRAS; and (4) they are observable from the northern hemisphere. Their radio and far infrared properties are summarized and their composite spectra are shown.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 483-484
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  • 48
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    IRAS observations of starburst galaxies (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Far infrared properties of Starburst galaxies were analyzed using IRAS observations at 25, 60, and 100 micrometers. Seventy-nine of 102 Starburst galaxies from the list of Balzano were detected. These galaxies have high IR luminosities of up to a few 10 to the 12th power L sub 0 and concentrate in a small area of the IR color - color diagram. The IR power law spectral indices, alpha, lie within the ranges -2.5 〈alpha(60,25)〈 -1.5 and -1.5 〈alpha(100,60)〈 0. These observed indices can be interpreted in terms of a cold disk component and a warm component. More than 80% of the 60 micrometer emission comes from the warm component. The fraction of the 60 micrometer emission attributable to the warm component can be used as an activity indicator.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 507-511
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  • 49
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    Ultraluminous infrared galaxies (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The IRAS survey of the local universe has revealed the existence of a class of ultraluminous infrared galaxies with L(8 to 1000 micrometer) greater than 10 to the 12th L sub 0 that are slightly more numerous, and as luminous as optically selected quasars at similar redshift. Optical CCD images of these infrared galaxies show that nearly all are advanced mergers. Millimeter wave CO observations indicate that these interacting systems are extremely rich in molecular gas with total H2 masses 1 to 3 x 10 to the 10th power M sub 0. Nearly all of the ultraluminous infrared galaxies show some evidence in their optical spectra for nonthermal nuclear activity. It is proposed that their infrared luminosity is powered by an embedded active nucleus and a nuclear starburst both of which are fueled by the tremendous reservoir of molecular gas. Once these merger nuclei shed their obscuring dust, allowing the AGN to visually dominate the decaying starburst, they become the optically selected quasars.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 411-420
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  • 50
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    Modelling the IRAS colors of galaxies (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: A physical interpretation is proposed for the color-color diagram of galaxies which are powered only by star formation. The colors of each galaxy result from the combination of two components: cirrus-like emission from the neutral disk, and warmer emission from regions directly involved in on-going star formation. This approach to modelling the emission is based on dust properties, but independent evidence for it is found in the relation between the color sequence and the luminosity sequence. Implications of data and interpretations are discussed and possible tests mentioned for the model.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 319-322
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  • 51
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    IRAS colors of VLA identified objects in the galaxy (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Infrared Astronomy Satellite (IRAS) sources found within 4 degrees of l = 125 deg, b = 2 deg on the 3rd HCON 60 micron Sky Brightness Images were observed at the Very Large Array (VLA). Regions were to be identified where massive stars are forming by looking for small areas of radio continuum emissions. The IRAS sources could be divided into three groups by their IRAS 12 micron/25 micron and 60 micron/100 micron color. The group identified with star forming regions contained essentially all of the objects with extended radio emission. In all of these cases the extended radio emission showed a morphology consistent with the identification of these objects as HII regions. The conclusion drawn is that star formation regions can be distinguished from other objects by their infrared colors.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 63-66
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  • 52
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    Infrared astronomy (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The role and contributions of Frank McDonald in extending high energy astrophysics to the sub-eV photon energy range (in putting infrared astronomy into orbit) are discussed.
    Schlagwort(e): ASTRONOMY
    Materialart: Essays in Space Science; p 395-401
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  • 53
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    X-ray astronomical spectroscopy (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The contributions of the Goddard group to the history of X-ray astronomy are numerous and varied. One role that the group has continued to play involves the pursuit of techniques for the measurement and interpretation of the X-ray spectra of cosmic sources. The latest development is the selection of the X-ray microcalorimeter for the Advanced X-ray Astrophysics Facility (AXAF) study payload. This technology is likely to revolutionize the study of cosmic X-ray spectra.
    Schlagwort(e): ASTRONOMY
    Materialart: Essays in Space Science; p 379-394
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  • 54
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    Hubble Space Telescope (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The Hubble Space Telescope will employ magnetic torque controllers, which make use of the Earth's magnetic field augmented by four reaction wheels. DC torques are easily allowed for, but variations, orbit by orbit, can result in excessive wheel speeds which can excite vibratory modes in the telescope structure. If the angular momentum from aerodynamic sources exceeds its allocation of 100 Nms, the excess has to come out of the maneuvering budget since the total capacity of the momentum storage system is fixed at 500 Nms. This would mean that maneuvers could not be made as quickly, and this would reduce the amount of science return. In summary, there is a definite need for a model that accurately portrays short term (within orbit) variations in density for use in angular momentum management analyses. It would be desirable to have a simplified model that could be used for planning purposes; perhaps applicable only over a limited altitude range (400 to 700 km) and limited latitude band.
    Schlagwort(e): ASTRONOMY
    Materialart: Upper and Middle Atmospheric Density Modeling Requirements for Spacecraft Design and Operations; p 73-87
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    Planetary radar astronomy (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The scientific aims, theoretical principles, techniques and instrumentation, and future potential of radar observations of solar-system objects are discussed in a general overview. Topics examined include the history of radar technology, echo detectability, the Arecibo and Goldstone radar observatories, echo time delay and Doppler shift, radar waveforms, albedo and polarization ratio, measurement of dynamical properties, and the dispersion of echo power. Consideration is given to angular scattering laws; the radar signatures of the moon and inner planets, Mars, and asteroids; topographic relief; delay-Doppler radar maps and their physical interpretation; and radar observations of the icy Galilean satellites of Jupiter, comets, and the rings of Saturn. Diagrams, drawings, photographs, and sample maps and images are provided.
    Schlagwort(e): ASTRONOMY
    Format: text
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  • 56
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    An atlas of optical spectrophotometry of Wolf-Rayet carbon and oxygen stars (1987)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-19
    Beschreibung: The atlas contains a homogeneous set of optical spectrophotometric observations (3300-7300 A) at moderate resolution (about 10 A) of almost all WC and WO stars in the Galaxy, the LMC, and the SMC. The data are presented in the form of spectral tracings (in magnitude units) arranged by subtype, with no correction for interstellar reddening. A montage of prototype stars of each spectral class is also shown. Comprehensive line identifications are given for the optical lines of WC and WO spectra, with major contributions tabulated and unidentified lines noted.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Journal Supplement Series (ISSN 0067-0049); 65; 459-483
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    Comments about observing conditions for UV astronomy aboard Spacelab (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The Spacelab missions provided a good opportunity for a first general UV survey of astrophysical objects. The UV observations carried out on Spacelab 1 yielded some new results, but revealed at the same time observing and operation constraints which must be considered for planning and preparing for future Spacelab experiments. Experience gained with two astronomical experiments, the UV Very Wide Field Camera (1ES022) and FAUST Far Ultraviolet Telescope (1NS-005) are discussed.
    Schlagwort(e): ASTRONOMY
    Materialart: Advances in Space Research (ISSN 0273-1177); 7; 5, 19
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  • 58
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    VLBI observations of the 3C 111 jet (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: VLBI observations have been made of the central component of the broad-line radio galaxy 3C 111 at 1.7 GHz and 5.0 GHz. High-dynamic-range maps at both frequencies show a one-sided jet in PA 62 + or - 1 deg but no counterjet. The lower limit to the jet/counterjet ratio is 30:1 at 5 GHz and 15:1 at 1.7 GHz. The jet is initially straight, but beyond 15 marcsec from the core it exhibits small bends or wiggles. Their onset corresponds to a sharp reduction in the rate of intensity falloff along the jet, suggesting that an instability in the jet is causing substantial particle acceleration.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 317; 121-127
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  • 59
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    Morphology of luminous IRAS galaxies: Summary talk (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: The author discusses the morphology of luminous Infrared Astronomy Satellite (IRAS) galaxies. A few comments are made about the direction to be taken in future observations of luminous IRAS galaxies.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 753-756
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  • 60
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    Summary of symposium: Low luminosity sources (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: The author summarized certain aspects of the conference. He shares this task with another colleague thereby breaking the task into more manageable proportions. The author covers the low luminosity sources. He begins his review with a summary of some major themes of the conference and ends with a few speculations on possible theoretical mechanisms.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 743-752
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  • 61
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    IRAS observations of AGN candidates at low flux levels (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: IRAS additional observations were used to obtain a sample of point sources at much fainter flux levels than hitherto available through the IRAS Point Source Catalogue. This sample is being used to compile an incomplete but representative catalogue of faint IRAS candidate Active Galactic Nuclei (AGNs) and to study the evolution of the infrared bright galaxies. Ground based follow up observations (optical spectroscopy) are mainly hampered by identification confusion.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 693-698
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  • 62
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    Extragalactic OH megamasers in strong IRAS sources (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: From the OH and HI survey of the strongest far infrared IRAS sources, 3 new powerful OH megamasers were discovered in Arp 143, IRAS 1510+0724 and in the uncatalogued IRAS source, IRAS 17208-0014. The HI line, the OH 1667 and 1665 MHz main lines and the 21 cm continuum observations were made with Nancy radio telescope. The optical spectra and images were obtained at the European Southern Observatory. The spectra are displayed in figures together with the main IR and OH properties of the 8 megamasers detected up to now, including IC 4553, NGC 3690 and Mrk 231, Mrk 273 and III ZW35.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 597-600
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  • 63
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    What are cirrus point sources? (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Most cirrus point sources are associated with interstellar gas. A subset of these was isolated, together with other sources showing large band 4 to 3 flux density ratios, that are not associated with interstellar gas. Most of the point sources are associated with diffuse cirrus emissions. The sources appear to be distributed randomly on the sky, with the exception of six clusters, one of which is not associated with any known object. Six sources out of seventeen that were observed for redshifted H I at Arecibo were found to be associated with relatively nondescript external galaxies. Most of the sources do not appear on the Palomar Sky Survey. Deep optical observations of eight fields revealed some fairly distant galaxies, one object with a very peculiar optical spectrum, and several blank fields.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 553-558
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  • 64
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    Systematic identification of IRAS point sources (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: A large scale program was initiated to identify IRAS point sources. At ROE the ideal facilities are at hand to undertake such a large program, viz. the rapid scanning capabilities of the COSMOS measuring machine to exploit the depth and resolution of the U.K. Schmidt Telescope J survey plates. Sources in 44 Schmidt plate areas were identified including 1300 sources and covering 1100 square degrees. The identification comprise 700 galaxy identifications and 600 stellar identifications. There are also about 40 sources with no obvious identification but which can be most easily explained by cirrus, confusion between two sources or sources just outside the 2 sigma error box. A major aim with the galaxy identification is to provide a data base from which sound statistical analyses can be made. Accurate blue magnitudes and morphological classifications for each identification were produced.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 537-545
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  • 65
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    A near-infrared study of the luminous merging galaxies NGC 2623 and ARP 148 (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: As part of an investigation of the physical mechanisms which produce large infrared luminosities in interacting systems, multicolor near-infrared maps were obtained of the long tailed galaxy NGC 2623 and the ring galaxy Arp 148. The near-infrared broadband spectrum was decomposed to obtain the contribution of four processes: emission from evolved stars, nebular continuum emission, thermal reradiation, and extinction. This multicolor analysis, along with 2 micrometer maps and 10 micrometer measurements, is used to determine the structure of these interacting galaxies and to delineate regions of star formation.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 515
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  • 66
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    Characteristics of UGC galaxies detected by IRAS (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Infrared Astronomy Satellite (IRAS) detection rates at 60 microns were determined for the Uppsala General Catalog of Galaxies (Nilson 1973; the UCG). Late-type spirals, characterized by a normal IR/B ratio of approximately 0.6, are detected to a velocity of approximately 6000 km/s for L sub B = L sub *. Contrary to the situation for IRAS-selected galaxy samples, little evidence was found for a correlation between IR/B and 60/100 microns in this large optically-selected sample. Thus a significant fraction of the IRAS-measured far-infrared flux from normal spirals must originate in the diffuse interstellar medium, heated by the interstellar radiation field. Support was not found for Burstein and Lebofsky's (1986) conclusion that spiral disks are optically thick in the far-infrared.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 273-276
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  • 67
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    Spectral classification of emission-line galaxies (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: A revised method of classification of narrow line active galaxies and H II region-like galaxies is proposed. It involves the line ratios (O III) lambda 5007/H beta, (N II) lambda 6583/H alpha, (S II) (lambda lambda 6716 = 6731)/H alpha, and (O I) lambda 6300/H alpha. These line ratios take full advantage of the physical distinction between the two types of objects and minimize the effects of reddening correction and errors in the flux calibration. Large sets of internally consistent data are used including new previously unpublished measurements. Prediction of recent photoionization models by power law spectra and by hot stars are compared with the observations. The classification is based on the observational data interpreted on the basis of these models.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 737-740
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  • 68
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    Far-infrared properties of optically-selected quasars and Seyfert galaxies (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Pointed IRAS observations and ground based observations are used to determine the infrared properties of optically selected galaxies and quasars. The use of complete, unbiased, optically selected samples means that statistical tests can be applied to probe the underlying properties of active galactic nuclei (AGNs). The near infrared to millimeter spectral energy distributions (SEDs) were studied of the CfA Seyfert galaxies, a well defined, unbiased sample of 25 Type 1 and 23 Type 2 Seyfert galaxies selected by optical spectroscopy. Data given show strong trends in the infrared SEDs. Strong evidence is also given that the infrared spectra of Seyfert 2 galaxies are dominated by thermal emission from warm dust, while nonthermal emission is more important in the spectra of quasars and luminous Seyfert 1 nuclei.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 723-725
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  • 69
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    Circumnuclear starbursts in Seyfert galaxies (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Observational diagnostics for the recognition of circumnuclear star formation in Seyfert galaxies are described and illustrated. These methods include: (1) spatially resolved optical spectroscopy, which allows the emission lines for HII regions to be separated from those originating in gas ionized by the Seyfert nucleus; (2) radio continuum mapping, where the linear radio sources characteristic of the nuclear activity may be distinguished from the diffuse morphology of multiple supernova remnants generated in a starburst; (3) infrared spectroscopic searches for emission features of dust, which are seen in starbursts but not in Seyfert nuclei; (4) the shape of the IRAS spectrum. These various diagnostics agree well as to the presence or absence of ongoing star formation. The IRAS spectra of a significant fraction of Seyferts are dominated by emission from dust heated by stars, not the Seyfert nucleus itself. In these cases, the spectrum is curved, being steep between 25 and 60 microns and flatter between 60 and 100 microns. When the Seyfert nucleus dominates, the 25 to 100 micron spectrum is much flatter. It is suggested that the location of a Seyfert galaxy in the IRAS color-color diagram reflects primarily the relative contributions of the active nucleus and dust heated by stars to the infrared fluxes.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 675-691
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  • 70
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    Spatial deconvolution of IRAS galaxies at 60 UM (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Using IRAS in a slow scan observing mode to increase the spatial sampling rate and a deconvolution analysis to increase the spatial resolution, several bright galaxies were resolved at 60 micron. Preliminary results for M 82, NGC 1068, NGC 3079 and NGC 2623 show partially resolved emission from 10 to 26 arcsec., full width at half maximum, and extended emission from 30 to 90 arcsec. from the center. In addition, the interacting system, Arp 82, along with Mark 231 and Arp 220 were studied using the program ADDSCAN to average all available survey mode observations. The Arp 82 system is well resolved after deconvolution and its brighter component is extended; the two most luminous objects are not resolved with an upper limit of 15 arcsec. for Arp 220.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 651-660
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  • 71
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    Ground-based follow up of IRAS galaxies (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Optical, near infrared, radio continuum and HI observations were undertaken of the galaxies identified with IRAS sources in a few fields roughly of the size of a sky survey plate. Results are presented from two fields at galactic latitude +27 and +43 deg over a total area of 100 sq. deg. These regions contained 115 IRAS point sources, out of which 26 were identified with stars and 81 with faint galaxies, 10 of which were difficult to recognize on the Schmidt plates. Spectroscopy was obtained with the ESO telescopes at a resolution of about 10 A. The vast majority of galaxies have low excitation spectra dominated by low ionization lines. The spectra are typical of HII region type galaxies, however of much lower excitation that other starbursts galaxies. The importance of the reddening as determined from the H alpha/H beta ratio is stressed: the visual absorption A sub v ranges from 2 to 6 magnitudes and as a consequence the corrected L sub IR/L sub B ratios are considerably reduced if those reddenings apply to the whole galaxy.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 605-609
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  • 72
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    Optical and IR luminosity functions of IRAS galaxies (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: The optical and infrared luminosity functions are determined for a 60 micron flux-limited sample of 68 IRAS galaxies covering a total area of 150 deg sq. The IR function is in good agreement with that obtained by other authors. The shape of the optical luminosity function is similar to that of optically selected galaxy samples. The integrated light of most objects in the sample have (NII) to H alpha line flux ratios characteristic of HII-region galaxies. In the absolute magnitude range M sub J = -18, -22 about 14% of late-type galaxies are IRAS galaxies. The apparent companionship frequency is about twice as large as that for a comparable sample of non-IRAS late-type galaxies.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 569-572
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    Properties of the unusual galaxy PSC 09104+4109 (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: The IRAS source PSC 09104+4109 is tentatively identified with a faint emission line galaxy having z = 0.442. Assuming this identification is correct, the total infrared luminosity of this galaxy is estimated to be 5 x 10 to the 12th power L sub 0, among the highest for galaxies detected by IRAS. This energy is concentrated at wavelengths less than 30 micrometers, and is approx. 50 times greater than the estimated optical luminosity. The serendipitous way in which this source was found in the PSC catalog suggests that many more similar objects may be found at the lowest levels of the IRAS survey.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 559-562
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  • 74
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    The luminosity function of the brightest galaxies in the IRAS survey (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Results from a study of the far infrared properties of the brightest galaxies in the IRAS survey are described. There is a correlation between the infrared luminosity and the infrared to optical luminosity ratio and between the infrared luminosity and the far infrared color temperature in these galaxies. The infrared bright galaxies represent a significant component of extragalactic objects in the local universe, being comparable in space density to the Seyferts, optically identified starburst galaxies, and more numerous than quasars at the same bolometric luminosity. The far infrared luminosity in the local universe is approximately 25% of the starlight output in the same volume.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 523-530
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  • 75
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    Far-infrared activity and starburst galaxies (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: After the IRAS discovery of galaxies with large far-infrared to blue luminosity ratio, it has been proposed that an enhanced star formation could be the origin of the far-infrared emission through dust heating. Whether a simple photometric model is able to account for the FIR and optical properties of IRAS galaxies was investigated. The L sub IR/L sub B ratio, (B-V) color and H sub alpha equivalent width of normal spirals are well reproduced with smooth star formation histories. In the case of starburst galaxies, several theoretical diagrams allow us to estimate the burst strength and extinction. L sub IR/L sub B ratio up to 100 can be rather easily reached, whereas extreme values probably require IMF truncated at the low end.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 501-505
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    Detection of CO (J=1-0) in the dwarf elliptical galaxy NGC 185 (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: The detection of CO (J = 1-0) emission in the dwarf elliptical galaxy NGC 185 is reported. The presence of massive molecular clouds in this early-type galaxy supports the idea of recent or ongoing stellar formation indicated by the population of blue stars in the center. The CO was detected in two positions in the galaxy, the center, and a prominent dustcloud. The emission profile has two peaks, roughly centered around the systemic velocity. It is found that NGC 185 is overluminous in blue light for its CO luminosity compared with Sc galaxies. This might indicate a higher star-formation efficiency for NGC 185 than for the late-type galaxies.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 331-332
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    The onset of chromospheric activity among the A- and F- type stars (1987)
    In:  Other Sources
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    Publikationsdatum: 2019-01-25
    Beschreibung: IUE observations of C II lambda1335 and C IV lambda1549 and ground-based observations of He I lambda5876 have previously discovered intense levels of chromospheric activity among early F type stars. Virtually all F dwarfs show stronger chromospheric and transition region emission than do the cooler and more deeply convective dwarf stars like the Sun. The IUE spectra and those of He lambda5876 place the onset of stellar activity along the main sequence near a color B - V = 0.28, which corresponds approximately to spectral type FO and an effective temperature of 7300 K. However, existing X-ray observations of A and F stars suggest that coronal activity may reach a peak blueward of this high temperature boundary at B - V = 0.28 before vanishing among the early and mid A-type stars. Discussed are preliminary results of a new effort to refine the location of the high temperature boundary to chromospheric activity among A- and F- type stars, making use of low dispersion short-wavelength spectra from the IUE archives from which the strengths of C IV, C II, and Lyman alpha emission have been measured.
    Schlagwort(e): ASTRONOMY
    Materialart: Colorado Univ., 5th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun; 1 p
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    An astrometric facility for planetary detection on the Space Station (1987)
    In:  Other Sources
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    Publikationsdatum: 2018-12-01
    Beschreibung: The preliminary system definition study for an Astrometric Telescope Facility (ATF) designed for the Space Station IOC is discussed, and a strawman system is designed which is found to meet the requirements for extrasolar planetary systems search and study. The strawman facility design, with a prime-focus 1.25-m aperture telescope and an f ratio of 13, was selected to minimize random and systematic errors. A basic operations approach is identified, including the approach to launch, initial on-orbit assembly and checkout, normal operations, and the response to anomolous conditions or failures. The preliminary system is designed to be fail-safe and single-fault tolerant. Mission analysis indicates that the basic viewing required for planetary detection can be accomplished in about 2/3 of the total viewing time.
    Schlagwort(e): ASTRONOMY
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  • 79
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    Nonlinear force-free magnetic fields: Calculation and applicatin to astrophysics (1987)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: The problem concerned in this work is that of calculating magnetic field configurations in which the Lorentz force (vector)j x (vector)B is everywhere zero, subject to specified boundary conditions. The magnetic field is represented in terms of Clebsch variables in the form (vector)B = del alpha x del beta. These variables are constant on any field line. The most appropriate choice of boundary conditions is to specify the values of alpha and beta on the bounding surface. It is proposed that the field lines move in the direction of local Lorentz force and relax towards a force-free field configuration. This concept leads to an iteration procedure for modifying the variables alpha and beta that tends asymptotically towards the force-free state. This method is first applied to a simple problem in two rectangular dimensions; the calculation shows that the convergence of magnetic field energy to a minimum state (force-free) is close to exponential. This method is then applied to study some astrophysical force-free magnetic fields, such as the structures and evolution of magnetic fields of rotating sunspots and accretion disks. The implication of the results, as related to the mechanisms of solar flares, extragalactic radio sources and radio jets, are discussed.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA-CR-181196 , NAS 1.26:181196 , CSSA-ASTRO-87-11
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    Fifty Year Canon of Solar Eclipses: 1986 - 2035 (1987)
    In:  CASI
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    Publikationsdatum: 2019-06-28
    Beschreibung: A complete catalog is presented, listing the general characteristics of every solar eclipse from 1901 through 2100. To complement this catalog, a detailed set of cylindrical projection world maps shows the umbral paths of every solar eclipse over the 200 year interval. Focusing in on the next 50 years, accurate geodetic path coordinates and local circumstances for the 71 central eclipses from 1987 through 2035 are tabulated. Finally, the geodetic paths of the umbral and penumbral shadows of all 109 solar eclipses in this period are plotted on orthographic projection maps of the Earth. Appendices are included which discuss eclipse geometry, eclipse frequency and occurrence, modern eclipse prediction and time determination. Finally, code for a simple Fortran program is given to predict the occurrence and characteristics of solar eclipses.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA-RP-1178-REV , REPT-87B0252 , NAS 1.61:1178-REV
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  • 81
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    Observations made with the International Ultraviolet Explorer (1987)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: Observations were made with the International Ultraviolet Explorer of two quite diverse astronomical objects. The first is an extremely ultraviolet excess star projected near the globular cluster M5. The second is a previously unrecognized but very bright starburst galaxy. Each of these objects is discussed in detail.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA-CR-181117 , NAS 1.26:181117
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  • 82
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    IRAS observations of BL Lac objects (1987)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: IRAS data was analyzed for 35 BL Lac objects selected from a complete 5 GHz radio sample, using the coadded survey database. The detection rate is 50% with more than 40% detected in more than one band. This compares with only 15% of these sources that are included in the IRAS Point Source Catalog. High luminosity BL Lac objects generally have smooth energy spectra over four or five decades in frequency, consistent with incoherent synchrotron emission from 1 cm to 1 micron. However, many low luminosity BL Lac objects have discontinuous spectra, with a large range in the spectral index at IRAS wavelengths. For BL Lacs with a total luminosity of less than 10 to the 44th power ergs/-s, most of the far infrared energy probably originates from dust heated near the galaxy nucleus. The energy budget shows that the majority of the power per unit bandwidth emerges in the infrared (1 to 100 microns).
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 731-735
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  • 83
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    VLA observations of a sample of galaxies with high far-infrared luminosities (1987)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: Preliminary results are presented from a radio survey of galaxies detected by the IRAS minisurvey. It was found that the main difference between galaxies selected in the far infrared and those selected in the optical is that the former have higher radio luminosities and that the radio emission is more centrally concentrated. There is some evidence that the strong central radio sources in the galaxies selected in the infrared are due to star formation, the star formation rate divided by the volume in which the star formation is occuring is 100 to 1000 times greater in the galaxies selected in the infrared than in the disks of normal galaxies.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 531-536
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  • 84
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    Interferometric CO observations of the ultraluminous IRAS galaxies ARP 220, IC 694/NGC 3690, NGC 6420 and NGC 7469 (1987)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: High resolution CO observations of the IRAS galaxies Arp 220, IC 694/NGC 3690, NGC 6240 and NGC 7469 were made with the Millimeter Wave Interferometer of the Owen Valley Radio Observatory. These yield spatial information on scales of 1 to 5 kpc and allow the separation of compact condensations from the more extended emission in the galaxies. In the case of the obviously interacting system IC 694/NGC 3690 the contributions of each component can be discerned. For that galaxy, and also for Arp 220, the unusually high lumonisities may be produced by nonthermal processes rather than by intense bursts of star formation.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 471-475
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  • 85
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    CO observations of nearby galaxies and the efficiency of star formation (1987)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: The CO distributions and total molecular content of 160 galaxies were observed using the 14 meter millimeter telescope of the FCRAO. For the luminous, relatively face-on Sc galaxies, the azimuthally averaged CO distributions are centrally peaked, while for the Sb and Sa galaxies the Co distributions often exhibit central CO holes up to 5 kpc across. None of the Sc galaxies have CO distributions which resemble the Milky Way. A general correlation was found between total CO and IR luminosities in galaxies. The scatter in this relation is highly correlated with dust temperature. No strong correlation of IR luminosities was found with HI masses, and it was thereby concluded that the infrared emission is more directly tied to the molecular content of galaxies. It is suggested that galaxies which have high Star Formation Effiencies (SFEs) produce more stars per unit molecular mass, thereby increasing the average temperature of the dust in the star forming regions. Irregular galaxies and galaxies previously identified as mergers have the highest observed star formation efficiencies. For the mergers, evidence was found that the IR/CO luminosity ratio increases with the merger age estimated by Joseph and Wright (1985).
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 197-215
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  • 86
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    Infrared spectroscopy of star formation in galaxies (1987)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: The Brackett alpha and beta lines with 7.2 seconds angular and 350 km/s velocity resolution were observed in 11 infrared-bright galaxies. From these measurements extinctions, Lyman continuum fluxes, and luminosities due to OB stars were derived. The galaxies observed to date are NGC3690, M38, NGC 5195, Arp 220, NGC 520, NGC660, NGC1614, NGC 3079, NGC 6946, NGC 7714, and Maffei 2, all of which were suggested at some time to be starburst ogjects. The contributions of OB stars to the luminosities of these galaxies can be quantified from the measurements and range from insignificant to sufficient to account for the total energy output. The OB stellar luminosities observed are as high as 10 to the 12th solar luminosities in the galaxy NGC 1614. It is noteworthy that star formation can play very different roles in the infrared energy output of galaxies of similar luminosity, as for example Arp 220 and NGC 1614. In addition to probing the star formation process in these galaxies, the Brackett line measurements, when compared to radio and infrared continuum results, have revealed some unexpected and at present imperfectly understood phenomena: in some very luminous sources the radio continuum appears to be suppressed relative to the infrared recombination lines; in many galaxies there is a substantial excess of 10 micron flux over that predicted from simple models of Lyman alpha heating of dust if young stars are the only significant energy source.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 363-366
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  • 87
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    Ground-based 1- to 32-microns observations of ARP 220: Evidence for a dust-embedded AGN? (1987)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: New observations of the 10 and 20 micron size of the emission region in Arp 220 are presented. Also given are ground based photometry from 1 to 32 micron including measurements of the strength of the silicate feature at 10 micron. The results show that the 20 micron size of Arp is smaller than 1.5 arcsec (500 pc); comparison of IRAS and ground based observations show that IRAS 12 micron flux measured with a large arcmin beam is the same as that seen from the ground with a 3 arcsec aperture. At 10 micron a deep silicate absorption feature is seen that corresponds to a visual extinction of about 50 mag. These results suggest that a very significant portion of the 10 to the 12th power L sub 0 infrared luminosity from Arp 220 comes from a region less than or of the order of 500 pc in diameter. When these results are combined with recent measurement of a broad Brackett alpha line by DePoy and an unresolved 2.2 micron source by Neugebauer, Matthews and Scoville, a very attractive possibility for the primary luminosity source Arp 220 is a dust embedded compact Seyfert type nucleus.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 643-650
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  • 88
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    Near-infrared observations of IRAS minisurvey galaxies (1987)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: Near infrared photometry at J, H, and K was obtained for 82 galaxies from the IRAS minisurvey. The near infrared colors of these galaxies cover a larger range in J-H and H-K than do normal field spiral galaxies, and evidence is presented of a tighter correlation between the near and far infrared emission in far infrared bright galaxies than exists between the far infrared and the visible emission. These results suggest the presence of dust in the far infrared bright galaxies, with hot dust emission contributing to the 2.2 micron emission, and extinction by dust affecting both the near infrared colors and the visible luminosities. In addition, there is some indication that the infrared emission in many of the minisurvey galaxies is coming from a strong nuclear component.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 601-604
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  • 89
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    Reflectance spectra of mafic silicates and phyllosilicates from .6 to 4.6 microns (1987)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: The results of spectral measurements for mafic silicates are given. The study provided valuable spectral reflectance information about mafic silicates and phyllosilicates in the 2.5 to 4.6 micron wavelength region. It was shown that the reflectance of these materials is strongly affected by the presence of H2O and OH. Therefore, the identification of these absorbing species is greatly enhanced.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington, Reports of Planetary Geology and Geophysics Program, 1986; p 187-189
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  • 90
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    IUE observations of Mg2 emission form Miras (1987)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: A total of 61 well exposed low dispersion LWP observations were obtained from the brightest normal M-type Mira variables around their pulsation cycles. By observing Mg II throughout the cycle, the intent is to determine the shock luminosity and duration, and the density in the upper atmospheres of Miras. The data also provide a mechanism for probing the radiative cooling in postshock regions of the atmosphere as a function of time. A summary of data acquired for IUE programs SRHLW and MGIEB is presented.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA-CR-180603 , NAS 1.26:180603
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  • 91
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    Astronomic Telescope Facility: Preliminary systems definition study report. Volume 2: Technical description (1987)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: The Astrometric Telescope Facility (AFT) is to be an earth-orbiting facility designed specifically to measure the change in relative position of stars. The primary science investigation for the facility will be the search for planets and planetary systems outside the solar system. In addition the facility will support astrophysics investigations dealing with the location or motions of stars. The science objective and facility capabilities for astrophysics investigations are discussed.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA-TM-89429-VOL-2 , A-87172 , NAS 1.15:89429-VOL-2
    Format: application/pdf
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  • 92
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    An astrometric facility for planetary detection on the space station (1987)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: An Astrometric Telescope Facility (ATF) for planetary detection is being studied as a potential space station initial operating capability payload. The primary science objective of this mission is the detection and study of planetary systems around other stars. In addition, the facility will be capable of other astrometric measurements such as stellar motions of other galaxies and highly precise direct measurement of stellar distance within the Milky Way Galaxy. The results of a recently completed ATF preliminary systems definition study are summarized. Results of this study indicate that the preliminary concept for the facility is fully capable of meeting the science objective without the development of any new technologies. A simple straightforward operations approach was developed for the ATF. A real-time facility control is not normally required, but does maintain a near real-time ground monitoring capability for the facility and science data stream on a full-time basis. Facility observational sequences are normally loaded once a week. In addition, the preliminary system is designed to be fail-safe and single-fault tolerant. Routine interactions by the space station crew with the ATF will not be necessary, but onboard controls are provided for crew override as required for emergencies and maintenance.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA-TM-89436 , A-87133 , NAS 1.15:89436
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  • 93
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    The HII regions in M51: Radio and optical observations (1987)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: High resoluton, dual frequency radio observations and calibrated H alpha surface photometry of the spiral galaxy M51 are used to determine the physical properties of the 40 brightest HII region complexes. M51 appears to have a normal HII region population when compared with other nearby Sc galaxies for which good data exist. The radio and H alpha data were used to measure the extinction toward the HII regions. The extinction is very patchy but appears to have a weak trend to become on the average smaller toward large galactocentric radii. This trend is consistent with a possible metallicity gradient in M51. The radio determined extinctions were compared with Balmer decrement extinctions and good agreement was found between the two, contrary to previous studies of M51 and other galaxies.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 235-238
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  • 94
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    Star formation in the merging Galaxy NGC3256 (1987)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: The central 5 kpc of the ultra-luminous merging galaxy NGC 3256 was mapped at J, H, K, L, and 10 micrometer, and a 2 micrometer spectra of the nuclear region was obtained. This data was used to identify and characterize the super starburst which has apparently been triggered and fuelled by the merger of two gas rich galaxies. It is also shown that the old stellar population has relaxed into a single spheroidal system, and that a supernova driven wind might eventually drive any remaining gas from the system to leave a relic which will be indistinguishable from an elliptical galaxy.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 517-519
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  • 95
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    A study of the fundamental characteristics of 2175A extinction (1987)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: The characteristics of interstellar extinction were studied in the region of the 2175 A feature for lines of sight which appear to exhibit unusually weak ultraviolet extinction. The analysis was based upon a parameterization of the observed extinction via fitting specific mathematical functions in order to determine the position and width of the 2175 A feature. The data are currently being analyzed.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA-CR-180926 , NAS 1.26:180926
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  • 96
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    Astrometric Telescope Facility preliminary systems definition study. Volume 1: Executive summary (1987)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: The Astrometric Telescope Facility (ATF) is a spaceborne observatory proposed for use on the Space Station (SS) as an Initial Operating Capability (IOC) payload. The primary objective of the ATF will be the search for extrasolar planetary systems and a detailed investigation of any discovered systems. In addition, it will have the capability of conducting other astrophysics investigations; e.g., measuring precise distances and motions of stars within our galaxy. The purposes of the study were to: (1) define mission and system requirements; (2) define a strawman system concept for the facility at the Prephase A level; (3) define the need for additional trade studies or technology development; and (4) estimate program cost for the strawman concept. It has been assumed for the study that the ATF will be a SS payload, will use a SS-provided Coarse Pointing System (CPS), will meet SS constraints, and will make maximum use of existing flight qualified designs or designs to be qualified by the SS program for general SS use.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA-TM-89429-VOL-1 , A-87113 , NAS 1.15:89429-VOL-1
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  • 97
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    Infrared source cross-index, first edition (1987)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: The Infrared Source Cross-Index is a listing of correlated infrared source names (and positions) for astronomical objects observed at 1-1000 microns. The source names have been obtained from the database of the first edition of the Catalog of Infrared Observations (CIO: NASA RP 1118), covering observations published through l982. Additional identifications were located by correlating these names with identifications contained in other machine-readable astronomical catalogs in the NASA National Space Science Data Center (NSSDC). There are some 80,000 different source names in the Cross-Index, corresponding to over 27,000 unique infrared sources.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA-RP-1182 , REPT-87B0058 , NAS 1.61:1182
    Format: text
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  • 98
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    X-ray astronomy experiments from sounding rockets (1987)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: During the past fourteen years, the M.I.T. X-ray Astronomy sounding rocket group has designed, fabricated, and flown five different scientific sounding rocket payloads. These experiment payloads were launched on a total of twelve sounding rocket flights of which only one failed because of rocket problems. Eight of these flights yielded astronomical data that resulted in a total of twelve publications. The bulk of this research was supported by NASA Grant NGR 22-009-730 X-Ray Astronomy Experiments Sounding Rockets. The fifth and final experiment payload conceived and built under this Grant (the Wide Field Soft X-ray Camera: WFSXC) served as the prototype for the British Wide Field Camera (WFC) experiment to be launched on the ROSAT mission. The five experiment payloads and the results obtained from these experiments are briefly described. In the case of the WFSXC, which served principally as an engineering prototype for a major space mission, a number of papers written by British collaborators which describe the ROSAT Wide Field Camera are presented.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA-CR-180112 , NAS 1.26:180112
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  • 99
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    Coordinated ultraviolet and radio observations of selected nearby stars (1987)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: All of the US2 shifts assigned were successfully completed with simultaneous International Ultraviolet Explorer (IUE) and the Very Large Array (VLA) observations of the proposed target stars. The target stars included dwarf M flare stars and RS CVn stars. The combined ultraviolet (IUE) and microwave (VLA) observations have provided important new insights to the radiation mechanisms at these two widely-separated regions of the electromagnetic spectrum. The VLA results included the discovery of narrow-band microwave radiation and rapid time variations in the microwave radiation of dwarf M flare stars. The results indicate that conventional radiation mechanisms cannot explain the microwave emission from these stars. In general, ultraviolet variations and bursts occur when no similar variations are detected at microwave wavelengths and vice versa. Although these is some overlap, the variations in these two spectral regions are usually uncorrelated, suggesting that there is little interaction between the activity centers at the two associated atmospheric levels.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA-CR-181089 , NAS 1.26:180189
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  • 100
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    Using SIRTF to study extragalactic star formation (1987)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: SIRTF, the Space Infrared Telescope Facility, is a NASA mission to provide a long lifetime, sensitive and flexible infrared observatory in space. SIRTF will be able to study selected objects with a sensitivity over 5,000 time better than the IRAS survey limits, and will provide photometric and low to medium resolution spectroscopic data over almost nine octaves from 1.8 to 700 micron wavelength. The baseline SIRTF design has an 85 cm telescope with optics and control system designed for diffraction limited operation at 4 micron and longer wavelengths. SIRTF will be able to measure important cooling lines from neutral regions, such as the 157 micron line, and lines from H II regions such as the 88 micron line. SIRTF will also be able to survey small areas of the sky to the confusion limit in the 3 to 700 micron region.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 629
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