Halo Mass-Concentration Relation at High-Mass End
  The concentration-mass (c-M) relation encodes the key information of the
assembly history of the dark matter halos, however its behavior at the high
mass end has not been measured precisely in observations yet. In this paper, we
report the measurement of halo c-M relation with galaxy-galaxy lensing method,
using shear catalog of the Dark Energy Camera Legacy Survey (DECaLS) Data
Release 8, which covers a sky area of 9500 deg^2. The foreground lenses are
selected from redMaPPer, LOWZ, and CMASS catalogs, with halo mass range from
10^{13} to 10^{15} M_sun and redshift range from z=0.08 to z=0.65. We find that
the concentration decreases with the halo mass from 10^{13} to 10^{14} M_sun,
but shows a trend of upturn after the pivot point of ~10^{14} M_sun. We fit the
measured c-M relation with the concentration model c(M)=C_0 (M/(10^{12}
M_sun/h)^{-\gamma} [1+(M/M_0)^{0.4}], and get the values (C_0, \gamma, log(M_0)
= (5.119_{-0.185}^{0.183}, 0.205_{-0.010}^{0.010}, 14.083_{-0.133}^{0.130}),
and (4.875_{-0.208}^{0.209}, 0.221_{-0.010}^{0.010}, 13.750_{-0.141}^{0.142})
for halos with 0.08<=z<0.35 and 0.35<=z<0.65, respectively. We also show that
the model including an upturn is favored over a simple power-law model. Our
measurement provides important information for the recent argument of massive
cluster formation process.
