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 _ { -0.23 } ^ { +0.34 } for the latter , are in remarkable agreement with slopes of \sim 0.9 - 1.0 predicted by the cold dark matter paradigm .
The tangential distortion signals in the radial range of 0.02 - 2 \mathrel { 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 \sim 0.2 , the total signal-to-noise ratio , S/N = 13.3 , is comparable to , or higher , because the enormous number of background source galaxies compensates for the low lensing efficiency of the nearby cluster .