SUBARU WEAK-LENSING SURVEY OF DARK MATTER SUBHALOS IN THE COMA CLUSTER: SUBHALO MASS FUNCTION AND STATISTICAL PROPERTIES

Okabe Nobuhiro

Futamase Toshifumi

Kijisawa Masaru

Kuroshima Risa

The Astrophysical Journal

We present a 4 deg^2 weak gravitational lensing survey of subhalos in the very nearby Coma cluster using the Subaru/Suprime-Cam. The large apparent size of cluster subhalos allows us to measure the mass of 32 subhalos detected in a model-independent manner, down to the order of 10^−3 of the virial mass of the cluster. Weak-lensing mass measurements of these shear-selected subhalos enable us to investigate subhalo properties and the correlation between subhalo masses and galaxy luminosities for the first time. The mean distortion profiles stacked over subhalos show a sharply truncated feature which is well-fitted by a Navarro–Frenk–White (NFW) mass model with the truncation radius, as expected due to tidal destruction by the main cluster. We also found that subhalo masses, truncation radii, and mass-to-light ratios decrease toward the cluster center. The subhalo mass function, dn/d ln M_sub, in the range of 2 orders of magnitude in mass, is well described by a single power law or a Schechter function. Best-fit power indices of 1.09^+0.42_−0.32 for the former model and 0.99^+0.34_−0.23 for the latter, are in remarkable agreement with slopes of ∼0.9–1.0 predicted by the cold dark matter paradigm. The tangential distortion signals in the radial range of 0.02–2 h^−1 Mpc from the cluster center show a complex structure which is well described by a composition of three mass components of subhalos, the NFW mass distribution as a smooth component of the main cluster, and a lensing model from a large scale structure behind the cluster. Although the lensing signals are 1 order of magnitude lower than those for clusters at z ∼ 0.2, the total signal-to-noise ratio, S/N = 13.3, is comparable, or higher, because the enormous number of background source galaxies compensates for the low lensing efficiency of the nearby cluster.

galaxies: clusters: individual (Coma Cluster (A1656)) – gravitational lensing: weak – X-rays: galaxies: clusters

Astronomy. Space sciences [ 440 ]

eng

IOP Publishing

© 2014. The American Astronomical Society. All rights reserved.

[ISSN] 0004-637X

[ISSN] 1538-4357

[NCID] AA00553253

[DOI] 10.1088/0004-637X/784/2/90

[DOI] https://doi.org/10.1088/0004-637X/784/2/90