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Dissertation
Photometric and spectroscopic properties of void galaxies in the Sloan Digital Sky Survey
Doctor of Philosophy (Ph.D.), Drexel University
Mar 2004
DOI:
https://doi.org/10.17918/etd-270
Abstract
Using a nearest neighbor analysis, we construct a sample of void galaxies from the Sloan Digital Sky Survey (SDSS) and compare the photometric and spectroscopic properties of these galaxies to the population of non-void (wall) galaxies. We trace the density field of galaxies using a volume-limited sample with z[max] = 0.089. Galaxies from the flux-limited SDSS with z [less than or equal to] z[max] and fewer than three volume-limited neighbors within 7h⁻¹Mpc are classified as void galaxies. This criterion implies a density contrast [delta][rho]/[rho] < -0.6 around void galaxies. From 155,000 galaxies, we obtain a sub-sample of 13,742 galaxies with z [less than or equal to] z[max], from which we identify 1,010 galaxies as void galaxies. To identify an additional 194 faint void galaxies from the SDSS in the nearby universe, r [approximately less than] 72h⁻¹Mpc, we employ volume-limited samples extracted from the Updated Zwicky Catalog and the Southern Sky Redshift Survey with z[max] = 0.025 to trace the galaxy distribution. Our void galaxies span a range of absolute magnitude from M[r] = -13.5 to M[r] = -22.5. Using SDSS photometry, we compare the colors, concentration indices, and Sersic indices of the void and wall samples. Void galaxies are on average significantly bluer than galaxies lying at higher densities. The population of void galaxies with M[r] [approximately less than] M* + 1 and brighter is on average bluer and more concentrated (later type) than galaxies outside of voids. The latter behavior is only partly explained by the paucity of luminous red galaxies in voids. These results generally agree with the predictions of semi-analytic models for galaxy formation in cold dark matter models, which indicate that void galaxies should be relatively bluer, more disklike, and have higher specific star formation rates. Analysis of their spectroscopic properties confirms that void galaxies have a higher specific star formation rate than wall galaxies and although they have comparable metallicities to galaxies in higher density regions, there is a deficiency of metal-poor galaxies in dense environments (Hao et al. 2003). From the luminosity function (LF) of void galaxies (Hoyle et al. 2003) we infer that voids are not filled with a large population of dwarf galaxies based on the similarities of the faint end slopes of void and wall galaxy LFs. In addition, the fainter value of M[r]* for void galaxies is consistent with our analysis of their photometric properties. Our results show that void galaxies differ from wall galaxies in most of the properties under consideration with a high statistical significance. This seems to indicate that void galaxies do occupy a special region of the parameter space manifold of galaxy properties.
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Details
- Title
- Photometric and spectroscopic properties of void galaxies in the Sloan Digital Sky Survey
- Creators
- Randall R. Rojas - DU
- Contributors
- Michael Scott Vogeley (Advisor) - Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- College of Arts and Sciences; Physics; Drexel University
- Other Identifier
- 270; 991014632589404721