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  • 1
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    Selection effects and binary galaxy velocity differences (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Measurements of the velocity differences (delta v's) in pairs of galaxies from large statistical samples have often been used to estimate the average masses of binary galaxies. A basic prediction of these models is that the delta v distribution ought to decline monotonically. However, some peculiar aspects of the kinematics have been uncovered, with an anomalous preference for delta v approx. equal to 72 km s(sup-1) appearing to be present in the data. The authors examine a large sample of binary galaxies with accurate redshift measurements and confirm that the distribution of delta v's appears to be non-monotonic with peaks at 0 and approx. 72 km s (exp -1). The authors suggest that the non-zero peak results from the isolation criteria employed in defining samples of binaries and that it indicates there are two populations of binary orbits contributing to the observed delta v distribution.
    Keywords: ASTROPHYSICS
    Type: NASA, Marshall Space Flight Center, Paired and Interacting Galaxies: International Astronomical Union Colloquium No. 124; p 485-490
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  • 2
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    Massive low surface brightness galaxies (1993)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: A multi-wavelength study of an extreme type of galaxy which will assist us in our attempts to understand the formation and evolution of galaxies was completed. In particular, a subset of low surface brightness (bar-mu(sub B) is approximately greater than 25 mag arcsec(sup -2)), giant galaxies (LSBG's) which contain large amounts of atomic gas (M(HI) is approximately greater than 10(exp 10) solar mass), have blue optical diameters similar to those of giant spiral galaxies, but which do not seem to have prodigious amounts of ongoing star formation were observed. Our sample was drawn from the first and second Palomar Sky Surveys. This population of galaxies has been largely ignored because of selection effects which make it difficult to detect optically. The question of how these massive systems differ from the higher surface brightness 'normal' spiral galaxies is addressed. Using B and R surface photometry, in conjunction with H-alpha, HI, CO-12, and far-infrared data, an attempt is made to determine if these galaxies had an early epoch of star formation that has since faded, have ongoing star formation with an unusual interplanetary magnetic field (IMF), or are perhaps galaxies which have never efficiently formed stars due to a lack of molecular clouds.
    Keywords: ASTROPHYSICS
    Type: NASA. Ames Research Center, The Evolution of Galaxies and Their Environment; p 84-85
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  • 3
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    Luminosity function of quasars at large redshifts from grism surveys (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: We have carried out a systematic search for emission-line objects through photometrically calibrated CCD grism surveys with the Palomar 200-inch telescope in transit mode, covering 62 square degrees. These surveys have yielded 141 quasars detected by their C IV or Ly-alpha emission in the redshift range 2.0 - 4.7. We use this sample and the known flux limits to derive the slope of the luminosity function and the space density above a given line luminosity, as a function of redshift. While space densities are approximately constant at redshifts 2.0 - 3.0, they are declining steeply for redshifts larger than 3.
    Keywords: ASTROPHYSICS
    Type: In: The space distribution of quasars; Proceedings of the Workshop, Victoria, Canada, June 3-5, 1991 (A93-28776 10-90); p. 109-114; Discussi
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  • 4
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    The HST Quasar Absorption-Line Key Project. 8: CCD imaging of Hubble Space Telescope quasar fields (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We present an analysis of CCD images of more than 100 quasars; many of the objects have been or will be observed in the Hubble Space Telescope (HST) Key Project Quasar Absorption-Line Survey. The data set consists of B, g, and i photometry of 117 quasars and deeper g (limiting magnitude of approximately equal 22) images of 101 quasar fields. Positions accurate to approximately equal 1 sec, measured with the Space Telescope Science Institute's Astrometric Support Program, are listed for all of the quasars in this study. Positions, magnitudes, and classifications of stars and galaxies located within approximately equal 100 sec of the quasars are given for all of the deep g data. The positions of the stars and galaxies relative to the quasar are accurate to approximately equal 0.5 sec. The results presented here can be used to prepare spectroscopic programs designed to obtain redshifts of galaxies in the fields of these quasars.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 106; 700; p. 646-669
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  • 5
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    Northern dwarf and low surface brightness galaxies. II - The Green Bank neutral hydrogen survey (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The paper reports neutral hydrogen observations of a large sample of dwarf and other low surface brightness galaxies. A detailed discussion and error analysis of the observations are presented, and spectra are displayed for 329 galaxies detected for the first time, or detected with substantially better signal-to-noise ratios than achieved previously. The positions on the sky of 667 galaxies meeting the present selection criteria north of delta = 38 deg are shown. The distribution of the redshifts of galaxies detected at Green Bank is illustrated. The Green Bank detections tapered off strongly below the median H I flux of 3.7 Jy km/s detected at Arecibo: only 12 percent of the Green Bank sample was detected with smaller fluxes.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal Supplement Series (ISSN 0067-0049); 81; 1 Ju
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  • 6
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    Gravitational lensing of quasars as seen by the Hubble Space Telescope Snapshot Survey (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Results from the ongoing HST Snapshot Survey are presented, with emphasis on 152 high-luminosity, z greater than 1 quasars. One quasar among those observed, 1208 + 1011, is a candidate lens system with subarcsecond image separation. Six other quasars have point sources within 6 arcsec. Ground-based observations of five of these cases show that the companion point sources are foreground Galactic stars. The predicted lensing frequency of the sample is calculated for a variety of cosmological models. The effect of uncertainties in some of the observational parameters upon the predictions is discussed. No correlation of the drift rate with time, right ascension, declination, or point error is found.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 394; 1 Ju; 51-60
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  • 7
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    A gravitational lens candidate with an unusually red optical counterpart (1992)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The properties of the strong radio source MG0414 + 0534 are described. It is found to display many of the properties expected in a gravitational lens system. At radio wavelengths and 0.5-arcsec resolution, MG0414 + 0534 is made up of four compact components whose unusual configuration and relative flux densities are similar to those found in confirmed four-image gravitational lens systems. At optical wavelengths three objects are detected, consistent with there being optical objects at the positions of the radio components, given the lower optical resolution. The radio and optical centroid positions agree within the astrometric errors, and the relative ordering of the fluxes is the same. The colors and radiooptical spectral indices are similar, but there are differences larger than the photometric errors and the measured variability (about 30 percent). Extinction by dust might simultaneously explain the unusually red color and the absence of light from a lens.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 104; 3 Se; 968-979
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  • 8
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    Radio properties of optically selected high-redshift quasars. I - VLA observations of 22 quasars at 6 cm (1992)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: A total of 22 optically selected high-redshift QSOs were obseved at 5 GHz with the VLA. The measured radio properties of low-redshift optically selected quasars indicate that radio emission should have been detected from 5-10 objects in this sample of high-redshift QSOs, but only one QSO was found to have a radio flux above the 5 sigma limit of roughly 0.2 mJy. Possible explanations of this finding are considered.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 103; 5 Ma
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  • 9
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    Hubble Space Telescope imaging of the large-redshift gravitational lens candidate 1208 + 1011 (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Four-color photometry obtained with the HST is consistent with the hypothesis that the light from the quasar 1208 + 1011 (z = 3.8) is gravitationally lensed. Guided exposures taken with the HST Planetary Camera resolve the quasar image into two point-source components separated by 0.476 +/- 0.004 arcsec. The intensity ratio of the components is approximately 4:1 in each of four broadband HST filters with mean wavelengths of 4352, 5416, 6898, and 8922 A. The HST photometry, when combined with high-resolution ground-based spectroscopy, rules out the possibility that the secondary component is a Galactic star. The limit on additional point sources is 3 percent of the brighter image for separations greater than 0.5 arcsec from the primary component and 5 percent of the brighter component for separations between 0.1 and 0.5 arcsec. If the gravitational lens is an ordinary galaxy, it would not have been detected on the HST images.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 392; 1 Ju; L1-L4
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  • 10
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    Hubble Space Telescope Wide Field Camera imaging of the gravitational lens 2237 + 0305 (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Images of the gravitational lens system 2237 + 0305, taken with the HST Wide Field Camera, are analyzed. Positions for the four quasar images, accurate to +/-0.015 arcsec, and relative magnitudes in U and R, accurate to +/-0.06 and 0.04 mag, respectively, are determined. The upper limits on the observed brightness of the fifth image are found to be less than or approximately equal to 7 percent of the brightest quasar image. The mass of the lens inside 0.9 arcsec is found to be 1.08 +/-0.02 x 10 exp 10 solar masses/h100 corresponding to a mass-to-light ratio in B of 12.3h100. This solar mass/solar luminosity estimate agrees with values obtained from stellar dynamics for other elliptical galaxies. A comparison of predictions from this mass model with the measured central velocity dispersion yields a distance-independent agreement to within 10 percent, assuming isotropic velocity dispersions.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 104; 3 Se; 959-967
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