Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994phdt........28m&link_type=abstract
PhD Dissertation, Harvard Univ. Boston, MA United States
Astronomy and Astrophysics
Astronomy
Astronomical Catalogs, Elliptical Galaxies, Extraterrestrial Matter, Galactic Clusters, Luminosity, Sky Surveys (Astronomy), Spiral Galaxies, Red Shift, Brightness, Color, Cosmology, Irregular Galaxies, Stellar Magnitude, Velocity Distribution
Scientific paper
We use the CfA Redshift Survey to explore three independent but related aspects of the nearby galaxy distribution. First, we examine the galaxy luminosity function (LF), a classical tool of observational cosmology. We compute the LF for a sample of over 9,000 galaxies from the CfA Redshift Survey based on apparent magnitudes from the Zwicky Catalogue of Galaxies and of Clusters of Galaxies. The shape of the CfA LF is consistent with a Schechter function for galaxies brighter than M(z) = -16.5, where M(z) is the absolute magnitude in the Zwicky system. The general LF reveals a preponderance of faint galaxies, many more than would be expected from an extrapolation of the brighter portion of the LF. We also compute the LF for galaxies of different morphological types. The LF for elliptical and SO galaxies is consistent with the LF for spiral galaxies. Magellanic spiral and irregular (Sm-Im) galaxies contribute most of the faint end excess to the general LF. The Sm-Im LF is much steeper toward faint magnitudes than LFs for other types of galaxies. The excess of faint, blue galaxies significantly increases the expected number of galaxies at faint blue apparent magnitude even for a nonevolving population of galaxies. This increase does not account for the excess of a factor of 5-15 in deep galaxy counts over the counts predicted by standard no-evolution models. We compute the redshift-space correlation function of the combined CfA Redshift Survey and Southern Sky Redshift Survey. The sample includes 14,166 galaxies distributed over more than a quarter of the sky. We use the anisotropy of the redshift-space correlation function to measure the second moment of the peculiar velocity distribution, sigma(l2). If we include all galaxies in the combined CfA + SSRS2 sample, we measure sigma(l2) = 565 +/- 196 km/s. Taken at face value, the large velocity dispersion appears surprisingly consistent with a range of models based on Omega = 1 cold dark matter. However, we demonstrate that this statistic is extremely sensitive to clusters of galaxies; a few rich clusters significantly enhance sigma(l2) in samples of this size. When we exclude clusters, the dispersion decreases to 372 +/- 99 km/s. In Chapter 4, we describe a survey of Zwicky galaxies at low Galactic latitude. This survey explores the coherence of structure on very large scales. In particular, we examine the connection between the Perseus-Pisces complex in the south Galactic cap and the Great Wall in the north Galactic cap. We find that these two vast structures are not simply connected across the region obscured by the Galactic plane. Instead, these structures form the boundaries of a network of voids with characteristic scale approximately 50h-1 Mpc.
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