1 research outputs found
Halo mass - concentration relation from weak lensing
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 170,640 isolated ~L* galaxies split into ellipticals and spirals, 38,236
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
10^{12} M_{sun} to 10^{15} M_{sun}. The resulting lensing signal is consistent
with an NFW or Einasto profile on scales outside the central region. We find
that the NFW concentration parameter c_{200b} decreases with halo mass, from
around 10 for galactic halos to 4 for cluster halos. Assuming its dependence on
halo mass in the form of c_{200b} = c_0 [M/(10^{14}M_{sun}/h)]^{\beta}, we find
c_0=4.6 +/- 0.7 (at z=0.22) and \beta=0.13 +/- 0.07, with very similar results
for the Einasto profile. The slope (\beta) is in agreement with theoretical
predictions, while the amplitude is about two standard deviations below the
predictions for this mass and redshift, but we note that the published values
in the literature differ at a level of 10-20% and that for a proper comparison
our analysis should be repeated in simulations. 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. [ABRIDGED]Comment: 17 pages, 5 figures, accepted to JCAP pending minor revisions that
are included in v2 here on arXi