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

Abstract

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, Mh. 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 < 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(Mh/M⊙) ∼ 12, the M∗-to-Mh 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 < 15 range. (3) The fraction of halos hosting blue centrals at Mh = 1011 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 Mh ≈ 7 × 1011 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.