TITLE:
Galaxy halo masses and satellite fractions from galaxy-galaxy lensing in the SDSS: stellar mass, luminosity, morphology, and environment
dependencies.
AUTHOR(S):
Rachel Mandelbaum (Princeton), Uros Seljak (ICTP), Guinevere Kauffmann (MPA-Garching),
Christopher M. Hirata (IAS), Jonathan Brinkmann (APO).
DATE:
2005 Nov 07 (arXiv, v1, posted); 2005 Nov 07 (MNRAS, submitted); 2006 Jan 18 (revised);
2006 Mar 30 (MNRAS, published); 2006 May 01 (arXiv, v2, posted).
AVAILABILITY:
arXiv astro-ph/0511164 (free);
Blackwell Synergy (requires
subscription).
PUBLICATION INFORMATION: Mon. Not. R. Astron. Soc. 368, 715--731, 2006.
ABSTRACT:
The relationship between galaxies and dark matter can be characterized by the halo
mass of the central galaxy and the fraction of galaxies that are satellites. Here we
present observational constraints from the SDSS on these quantities as a function of
r-band luminosity and stellar mass using galaxy-galaxy weak lensing, with a total
of 351,507 lenses. We use stellar masses derived from spectroscopy and virial halo
masses derived from weak gravitational lensing to determine the efficiency with which
baryons in the halo of the central galaxy have been converted into stars. We find that
an L* galaxy with a stellar mass of 6x1010Msun is hosted by a halo with mass of
1.4x1012h-1Msun, independent of morphology, yielding baryon conversion efficiencies
of 17(+10/-5) (early types) and 16(+15/-6) (late types) per cent at the 95 per cent CL (statistical, not including systematic
uncertainty due to assumption of a universal initial mass
function, or IMF). We find that for a given stellar mass, the halo mass is independent
of morphology below Mstellar = 1011Msun, in contrast to typically a factor of two
difference in halo mass between ellipticals and spirals at a fixed luminosity. This suggests
that stellar mass is a good proxy for halo mass in this range and should be used preferentially
whenever a halo mass selected sample is needed. For higher stellar masses,
the conversion efficiency is a declining function of stellar mass, and the
differences in
halo mass between early and late types become larger, reflecting the fact that most
group and cluster halos with masses above 1013Msun host ellipticals at the center, while
even the brightest central spirals are hosted by halos of mass below 1013Msun. We find
that the fraction of spirals that are satellites is roughly 10-15 per cent independent
of stellar mass or luminosity, while for ellipticals this fraction decreases with stellar
mass from 50 per cent at 1010Msun to 10 per cent at 3x1011Msun. We split the elliptical
sample by local density, and find that at a given luminosity there is no
difference in the
signal on scales below 100 h-1kpc between high and low density regions, suggesting
that tidal stripping inside large halos does not remove most of the dark matter from
the early type satellites.color="#20ff20">
ADS BIBLIOGRAPHIC CODE: 2006MNRAS.368..715M
COMMENTS: SDSS Publication #568.