期刊
ASTROPHYSICAL JOURNAL
卷 731, 期 2, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/731/2/89
关键词
galaxies: elliptical and lenticular, cD; galaxies: evolution; galaxies: interactions; galaxies: structure
资金
- Alfred P. Sloan Foundation
- National Science Foundation
- US Department of Energy
- National Aeronautics and Space Administration
- Japanese Monbukagakusho
- Max Planck Society
- Higher Education Funding Council for England
- American Museum of Natural History
- Astrophysical Institute Potsdam
- University of Basel
- University of Cambridge
- Case Western Reserve University
- University of Chicago
- Drexel University
- Fermilab
- Institute for Advanced Study
- Japan Participation Group
- Johns Hopkins University
- Joint Institute for Nuclear Astrophysics
- Kavli Institute for Particle Astrophysics and Cosmology
- Korean Scientist Group
- Chinese Academy of Sciences (LAMOST)
- Los Alamos National Laboratory
- Max-Planck-Institute for Astronomy (MPIA)
- Max-Planck-Institute for Astrophysics (MPA)
- New Mexico State University
- Ohio State University
- University of Pittsburgh
- University of Portsmouth
- Princeton University
- United States Naval Observatory
- University of Washington
We study the properties of massive galaxies at an average redshift of z similar to 0.34 through stacking more than 42,000 images of luminous red galaxies (LRGs) from the Sloan Digital Sky Survey (SDSS). This is the largest data set ever used for such an analysis and it allows us to explore the outskirts of massive red galaxies at unprecedented physical scales. Our image stacks extend farther than 400 kpc, where the r-band profile surface brightness reaches 30 mag arcsec(-2). This analysis confirms that the stellar bodies of LRGs follow a simple Sersic profile out to 100 kpc. At larger radii, the profiles deviate from the best-fit Sersic models and exhibit extra light in the r-, i-, and z-band stacks. This excess light can probably be attributed to unresolved intragroup or intracluster light or a change in the light profile itself. We further show that standard analyses of SDSS-depth images typically miss 20% of the total stellar light and underestimate the size of LRGs by 10% compared to our best-fit r-band Sersic model of n = 5.5 and r(e) = 13.1 kpc. If the excess light at r > 100 kpc is considered to be part of the galaxy, the best-fit r-band Sersic parameters are n = 5.8 and r(e) = 13.6 kpc. In addition, we study the radially dependent stack ellipticity and find an increase with radius from epsilon = 0.25 at r = 10 kpc to epsilon = 0.3 at r = 100 kpc. This provides support that the stellar light that we trace out to at least 100 kpc is physically associated with the galaxies themselves and may confirm that the halos of individual LRGs have higher ellipticities than their central parts. Lastly, we show that the broadband color gradients of the stacked images are flat beyond roughly 40 kpc, suggesting that the stellar populations do not vary significantly with radius in the outer parts of massive ellipticals.
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