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  • 1
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    Survey incompleteness and the evolution of the QSO luminosity function (1993)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: We concentrate on a type of QSO survey which depends on selecting QSO candidates based on combinations of colors. Since QSO's have emission lines and power-law continua, they are expected to yield broadband colors unlike those of stellar photospheres. Previously, the fraction of QSO's expected to be hiding (unselected) within the locus of stellar (U-J, J-F) colors was estimated at about 15 percent. We have now verified that the KK88 survey is at least 11 percent incomplete, but have determined that it may be as much as 34 percent incomplete. The 'missing' QSO's are expected to be predominantly at z less than or = 2.2. We have studied the proper motion and variability properties of all stellar objects with J less than or = 22.5 or F less than or = 21.5 in the SA 57 field which has previously been surveyed with a multicolor QSO search by KK88.
    Keywords: ASTROPHYSICS
    Type: NASA. Ames Research Center, The Evolution of Galaxies and Their Environment; p 7-8
    Format: application/pdf
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  • 2
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    Absolute proper motions to B approximately 22.5: Evidence for kimematical substructure in halo field stars (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Radial velocities have been obtained for six of nine stars identified on the basis of similar distances and common, extreme transverse velocities in the proper motion survey of Majewski (1992) as a candidate halo moving group at the north Galactic pole. These radial velocities correspond to velocities perpendicular to the Galactic plane which span the range -48 +/- 21 to -128 +/- 9 km/sec (but a smaller range, -48 +/- 21 to -86 +/- 19 km/sec, when only our own measurements are considered), significantly different than the expected distribution, with mean 0 km/sec, for a random sample of either halo or thick disk stars. The probability of picking such a set of radial velocities at random is less than 1%. Thus the radial velocity data support the hypothesis that these stars constitute part of a halo moving group or star stream at a distance of approximately 4-5 kpc above the Galactic plane. If real, this moving group is evidence for halo phase space substructure which may be the fossil remains of a destroyed globular cluster, Galactic satellite, or Searle & Zinn (1978) 'fragment.'
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 427; 1; p. L37-L41
    Format: text
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  • 3
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    Probabilities for gravitational lensing by point masses in a locally inhomogeneous universe (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Probability functions for gravitational lensing by point masses that incorporate Poisson statistics and flux conservation are formulated in the Dyer-Roeder construction. Optical depths to lensing for distant sources are calculated using both the method of Press and Gunn (1973) which counts lenses in an otherwise empty cone, and the method of Ehlers and Schneider (1986) which projects lensing cross sections onto the source sphere. These are then used as parameters of the probability density for lensing in the case of a critical (q0 = 1/2) Friedmann universe. A comparison of the probability functions indicates that the effects of angle-averaging can be well approximated by adjusting the average magnification along a random line of sight so as to conserve flux.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 336; 544-549
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  • 4
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    The peculiar velocity field in the Perseus-Pisces supercluster (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Results are reported from a program to study peculiar motions of galaxies in the Per-Psc supercluster. The data set consists of newly obtained CCD photometry and published 21-cm line widths for 320 spiral galaxies. The peculiar velocities of these objects are estimated using the Tully-Fisher relation, calibrated with respect to an independent sample of cluster galaxies. Analysis shows that the principal feature of the velocity field in the Per-Psc region is a coherent streaming toward the Local Group. Nearly all the galaxies well in the foreground (cz less than about 2000 km/sec) have negtive peculiar velocities of amplitude about 1000 km/sec. A great majority of objects in the background of the supercluster, out to redshifts of about 7000 km/sec, also have very large negative peculiar velocities. The supercluster ridge itself, at a redshift or about 5000 km/sec, appears to consist of positive and negative peculiar-velocity groups of galaxies, but with negative peculiar velocities predominating both in amplitude and in number of objects involved.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 351; L5-L8
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  • 5
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    Narrowband imaging and spectroscopy close to the nucleus of the Seyfert galaxy NGC 7682 (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Keel's (1985) report of a jet-like optical feature emanating from the nucleus of NGC 7682 is investigated. Deep CCD images of NGC 7682 were taken with narrowband filters centered on the redshifted wavelength of H-alpha + forbidden N II and on a nearby continuum region. The continuum-subtracted line images show no evidence of the jet feature, although numerous H II regions appear clearly, both close to the nucleus and in the extended spiral arm structure. Spectra were taken at various dispersions and position angles, including the supposed position angle of the jet. These data were used to obtain background-subtracted spectra at the precise location of the jet. No excess emission was detected above the background-galaxy contribution. The highest-resolution spectra were used to determine the redshift of the galaxy to high precision.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 93; 1054-105
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  • 6
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    A redshift survey toward a proposed void of galaxies suggested by the distribution of Abell clusters (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: A program of redshift measurements was carried out in a region of the sky in which a relative under-density of Abell clusters had been used to infer the presence of a large (diameter about 40/h Mpc) void in the general galaxy distribution. The purpose of this study was to investigate whether the large-scale distribution of galaxies is traced by the distribution of rich clusters. Redshifts are presented for 308 galaxies in the Zwicky Catalog in a 234 square degree region centered on R.A. about 2h, Decl. about 12 deg of which 229 have been newly measured. These data reveal a pattern of filamentary structure alternating with voids of characteristic diameter about 25-30/h Mpc, throughout the volume sampled. While the redshift data reveal an underdensity in the distribution of galaxies in the general region suggested by the Abell cluster distribution, they do not support the existence there of a 40/h Mpc diameter void.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 355; 393-400
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  • 7
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    The faint quasar luminosity function (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-08-27
    Description: Preliminary results of an expanded program to determine the faint-quasar luminosity function are described. Quasars have been selected in four fields totaling 1.2 sq deg from four-band photometry. Out of a total of 130 quasars with good spectroscopy, 37 have J greater than 21.5 and 46 have F greater than 21.0. The spectroscopic sample is representative of all of the color-selected candidates. An estimate of the luminosity function as a function of redshift is derived.
    Keywords: ASTROPHYSICS
    Type: In: The space distribution of quasars; Proceedings of the Workshop, Victoria, Canada, June 3-5, 1991 (A93-28776 10-90); p. 32-43; Discussion
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