The stellar-to-halo mass relation of local galaxies segregates by color

2015 
By means of a statistical approach that combines different semi-empirical methods of galaxy-halo connection, we derive the stellar-to-halo mass relations (SHMR) of local blue and red central galaxies. We also constrain the fraction of halos hosting blue/red central galaxies and the occupation statistics of blue and red satellites as a function of halo mass, M h. For the observational input we use the blue and red central/satellite galaxy stellar mass functions and two-point correlation functions in the stellar mass range of 9 < log(M */M ?)?<12. We find that: (1)?the SHMR of central galaxies is segregated by color, with blue centrals having a SHMR above that of red centrals; at log(M h/M ?) ~12, the M *-to-M h ratio of the blue centrals is 0.05, which is ~1.7?times larger than the value of red centrals. (2) The constrained scatters around the SHMRs of red and blue centrals are 0.14 and 0.11?dex, respectively. The scatter of the average SHMR of all central galaxies changes from ~0.20?dex to ~0.14?dex in the 11.3 < log(M h/M ?)?<15 range. (3) The fraction of halos hosting blue centrals at M ? is 87%, but at 2 ? 1012 M ? decays to ~20%, approaching a few percent at higher masses. The characteristic mass at which this fraction is the same for blue and red galaxies is M ?. Our results suggest that the SHMR of central galaxies at large masses is shaped by mass quenching. At low masses processes that delay star formation without invoking too strong supernova-driven outflows could explain the high M *-to-M h ratios of blue centrals as compared to those of the scarce red centrals.
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