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  • 11
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    Galaxy formation and the origin of the ionizing flux at large redshift (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The absence of any continuous Ly-alpha opacity from the intergalactic medium at z = 3-4.5 can be understood if a significant population of star-forming galaxies is present at these redshifts. It is shown that such galaxies can be present within the galaxy populations at B = 22 to 27. The expected ionization produced during galaxy formation is analyzed in terms of highly model-independent metal production arguments and it is concluded that (if such galaxies are dust-free and transparent to ionizing photons) then at least 4(H0/50 km/s Mpc)-cubed percent of galaxy formation would have to have occurred in this redshift range.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 348; 371-377
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  • 12
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    A search for eclipses of HD 114762 by a low-mass companion (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: HD 114762 has an unseen companion with a dynamical mass that satisfies the constraint mass sin i = 2.5 x 10 to the 31st gm. The companion is a good candidate for a planetary-mass object, but the inclination of its orbit is unknown and its mass is indeterminate. Tests were conducted for the specific case of a nearly edge-on orbit by looking for eclipses of HD 114762 by the companion. Although the a priori probability of an eclipse is low, this is a crucial case because the companion has its minimum mass if the orbit is edge on. No eclipses were found with a depth greater than 0.01 mag and, therefore, the inclination of the orbit of HD 114762 is less than 89 deg.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 99; 672-674
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  • 13
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    CO(J = 2 - 1) study of molecular clouds in the southwest arm of M31 (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The first map of M31 in the CO(J = 2 - 1) transition, covering a 3 arcmin by 3 arcmin section of the SW arm-interarm region, is presented. The CO spectra in the arm region defined by H II regions are characterized by strong, narrow features which are interpreted here to be giant molecular clouds with masses of a few 100,000 solar masses. The interarm emission is interpreted as an ensemble of small clouds with masses of a few 10,000 solar masses. On the arm about 70 percent of the emission comes from large clouds, while off the arm essentially all of it comes from small clouds. The mass surface density on this section of M31 is about that of a comparable section of the Scutum arm of the Galaxy. The velocities of the giant clouds in the arm are shifted with respect to the rest of the molecular and atomic gas by about 15 km/s. This may be due to cloud response to passage through the spiral arm potential.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 365; 195-207
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  • 14
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    First images of water vapor masers in the galaxy M33 (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The first successful VLBI observations of 10 extragalactic H2O masers in the M33 galaxy are reported. A spectral-line VLBI synthesis map is constructed, the first of any extragalactic H2O maser sources. The map has the lowest noise of any K-band spectral line VLBI map yet produced. The maser emission extends over about 300 milliarcseconds and is divided into 14 distinct spatial components, the strongest of which has a correlated flux density of about 0.7 Jy. The relative positions of some of these components are determined accurately enough to provide first-epoch measurements for proper motion studies. The characteristics of the maser are similar to those of the most powerful maser in the Galaxy, W49N. A compact H II region is found close to the maser which is 1 pc in diameter and whose emission measure is about 6 x 10 to the 7th pc/cm exp 6. This region is the compact component of a more extended H II complex that extends over about 100 pc.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 364; 513-526
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  • 15
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    The anomalous 3.43 and 3.53 micron emission features toward HD 97048 and Elias 1 - C-C vibrational modes of polycyclic aromatic hydrocarbons? (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The 5-8 micron spectra obtained toward the two protostellar sources, HD 97048 and Elias 1 exhibit strong anomalous emission features at 3.43 and 3.53 microns. Combining these results with earlier data established that the emission in the general IR features is extended on at least a 20-arcsec scale. In view of the high energy density in the emission zone, as well as the apparent correspondence of the anomalous 3.43 and 3.53 micron features with weak emission shoulders associated with the general family of IR emission bands, an explanation for these observations in terms of C-C overtones and combination tones of large or dehydrogenated polycyclic aromatic hydrocarbons is judged to be provisionally suitable.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 360; 577-589
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  • 16
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    Comment on 'Local generation of electrostatic bursts at Comet Giacobini-Zinner: Modulation by steepened magnetosonic waves' by A. L. Brinca et al (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 8287-828
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  • 17
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    Studies of H I and D I in the local interstellar medium (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: High-dispersion IUE spectra are presented of the hydrogen Ly-alpha chromospheric emission line of two nearby late-type stars, Capella and Lambda And. Both interstellar H I and D I Ly-alpha absorption can be seen against the chromospheric line, and the density, velocity dispersion, and bulk velocity of the gas in those lines of sight are derived. Limits are placed on the D/H ratio. The results are consistent with the current picture of the local interstellar medium.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 356; 223-228
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  • 18
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    Observations of 40-70 micron bands of ice in IRAS 09371 + 1212 and other stars (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: IRAS 09371 + 1212 is still an absolutely unique object. This M giant star, with circumstellar CO and a spectacular bipolar nebula, displays unique IRAS FIR colors which had been attributed to strong emission in the 40-70-micron bands of ice, as subsequently supported by the observation of a strong 3.1-micron absorption band. The results of the KAO observations have confirmed its unusual nature: the far-infrared bands of ice are by far the strongest known. Its dust temperature, 50 K or less, is by far the lowest known for a late-type circumstellar envelope.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 355; L27-L30
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  • 19
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    The physical and infrared spectral properties of CO2 in astrophysical ice analogs (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Results of measurements of the infrared spectroscopic and condensation-vaporization properties of CO2 in pure and mixed ices are presented. Detailed examination of five infrared CO2 bands, 2.20, 2.78, 4.27, 15.2, and 4.39 microns, shows that the peak position, FWHM, and profile of the bands provide important information about the composition, formation, and subsequent thermal history of the ices. Absorption coefficients and their temperature dependence for all five CO2 bands are determined. The temperature dependence variation is found to be less than 15 percent from 10 to 150 K, i.e., the temperature at which H2O ice sublimes. The number of parameters associated with the physical behavior of CO2 in CO2- and H2O-rich ices, including surface binding energies, and condensation and sublimation temperatures, are determined under experimental conditions. The implications of the data obtained for cometary models are considered.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 355; 357-372
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  • 20
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    Variations in the abundance of transiently heated particles within nearby molecular clouds (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: IRAS images of molecular clouds in the Chamaeleon, Taurus, and Ursa Major complexes show that the mid-IR emission from transiently heated particles is distributed very differently from the 100 micron emission from large dust grains. The ratio between 12 and 100 micron emission varies by more than one order of magnitude in each complex from about 5 times to about one-quarter of the average value in the solar neighborhood. Within a complex, color variations are seen on all scales. No significant variations of the I(v)(100 micron)/A(v) ratio are observed between clouds of widely different mid- to far-IR color. It is shown that neither the large amplitude of the color variations nor their morphology can be explained by changes of the excitation by the UV radiation field and it is concluded that the color variations trace variations in the abundance of transiently heated particles. A scenario is proposed which relates the abundance variations to the cycling of interstellar matter between the gas-phase and grain surfaces.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 364; 136-145
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