THE DEEP2 GALAXY REDSHIFT SURVEY: PROBING THE EVOLUTION OF DARK MATTER HALOS AROUND ISOLATED GALAXIES FROM z ～ 1 TO z ～ 0

摘要

Using the first 25% of the DEEP2 Redshift Survey data, we probe the line-of-sight velocity dispersion profile for isolated galaxies with absolute B-band magnitude -22 < M_B - 5 log(h) < -21 at z = 0.7-1.0, using satellite galaxies as luminous tracers of the underlying velocity distribution. Measuring the velocity dispersion beyond a galactocentric radius of ～200 h~(-1) kpc (physical) permits us to determine the total mass, including dark matter, around these bright galaxies. Tests with mock catalogs based on N-body simulations indicate that this mass measurement method is robust to selection effects. We find a line-of-sight velocity dispersion (σ_(los)) of 162_(-30)~(+44) km s~(-1) at ～110 h~(-1) kpc, 136_(-20)~(+26)km s~(-1) at ～230h~(-1) kpc, and 150_(-38)~(+55)km s~(-1) at ～320 h~(-1) kpc. Assuming an NFW model for the dark matter density profile, this corresponds to a mass within r_(200) of M_(200) = 5.5_(-2.0)~(+2.5) x 10~(12)h~(-1) solar mass for our sample of satellite hosts with mean luminosity ～2.5L~*. Roughly ～60% of these host galaxies have early-type spectra and are red in rest-frame (U - B) color, consistent with the overall DEEP2 sample in the same luminosity and redshift range. The halo mass determined for DEEP2 host galaxies is consistent with that measured in the Sloan Digital Sky Survey for host galaxies within a similar luminosity range relative to M_B~*. This comparison is insensitive to the assumed halo mass profile and implies an increase in the dynamical mass-to-light ratio (M_(200)/L_B) of isolated galaxies that host satellites by a factor of ～2.5 from z ～ 1 to z ～ 0. Our results can be used to constrain the halo occupation distribution and the conditional luminosity function used to populate dark matter halos with galaxies. In particular, our results are consistent with scenarios in which galaxies populate dark matter halos similarly from z ～ 0 to z ～ 1, except for ～ 1 mag of evolution in the luminosity of all galaxies. With the full DEEP2 sample, it will be possible to extend this analysis to multiple luminosity or color bins.