TITLE:
Halo mass - concentration relation from weak lensing.
AUTHOR(S):
Rachel Mandelbaum (IAS), Uros Seljak (Zurich), Christopher M. Hirata (Caltech).
DATE:
2008 May 16 (JCAP, submitted); 2008 May 16 (arXiv, v1, posted);
2008 Jun 20 (revised); 2008 Jul 07 (arXiv, v2, posted);
2008 Jul 07 (JCAP, accepted);
2008 Aug 06 (JCAP, published).
AVAILABILITY:
arXiv 0805.2552 (free);
IOP (free).
PUBLICATION INFORMATION:
JCAP 08, 006, 2008.
ABSTRACT:
We perform a statistical weak lensing analysis of dark matter profiles around tracers of halo mass
from galactic to cluster size halos. In this analysis we use 288 736 isolated ~L* galaxies split
into ellipticals and spirals, 43 335 groups traced by isolated spectroscopic Luminous Red Galaxies
(LRGs) and 13 823 MaxBCG clusters from the Sloan Digital Sky Survey (SDSS) covering a wide
range of richness. Together these three samples allow a determination of the density profiles of dark
matter halos over three orders of magnitude in mass, from 1012Msun to 1015Msun. The resulting lensing
signal is consistent with an NFW or Einasto profile on scales outside the central region. In the inner
regions, modelling of the proper identification of the halo center and inclusion of baryonic effects
from the central galaxy make the comparison less reliable. We find that the NFW concentration
parameter c200b decreases with halo mass, with typical values around 10 for galactic halo masses and
4 for cluster halos. Assuming its dependence on halo mass in the form of c = c0(M/1014h-1Msun)-β,
we find c0=4.6+/-0.7 and β=0.13+/-±0.07, with very similar results for the Einasto profile. The slope
(β) is in agreement with theoretical predictions, while the amplitude is about two standard devations
below the predictions for this mass and redshift, c~6, but we note that the published values in the
literature differ at a level of 10-20% and that for many analyses of simulations only relaxed halos
(which have higher concentrations) are used. This discrepancy could be further explained by the
residual effects due to cluster center misidentification, although we note that we see no evidence
of it on the scales used for this analysis, and that galaxies and groups also favor similarly low
concentrations. The dominant source of error is statistical at the low mass end, while at the high
mass end it is dominated by uncertainties in the identification of the halo center. We discuss the
implications of our results for the baryonic effects on the shear power spectrum: since these are
expected to increase the halo concentration, the fact that we see no evidence of high concentrations
on scales above 20% of the virial radius suggests that baryonic effects are limited to small scales,
and are not a significant source of uncertainty for the current weak lensing measurements of the
dark matter power spectrum.
ADS BIBLIOGRAPHIC CODE: N/A.
COMMENTS: SDSS Publication #875.