Subhalo abundance matching using progenitor mass at varying redshift: two modes of stellar mass growth imprinted into the Subaru HSC galaxy clustering

We propose a novel subhalo abundance matching (SHAM) model that uses the virial mass of the main progenitor of each (sub)halo M_prog as a proxy of the galaxy stellar mass M_* at the time of observation. This M_prog model predicts the two-point correlation functions depending on the choice of the epoch z_prog at which M_prog is quoted. With z_prog as a fitting parameter, we apply the M_prog model to the angular correlation functions measured with varying stellar mass thresholds from M_{*, lim}/(h^-2 M_⊙) = 10¹¹-10^8.6 using a sample of galaxies at z ≃ 0.4 from the Subaru Hyper Suprime-Cam survey. The M_prog model can reproduce the observations very well over 10 h^-1kpc-10 h^-1Mpc. We find that, for the samples of 10^9.2 ≤ M_{*, lim}/(h^-2 M_⊙) ≤ 10^10.2, the correlation functions predicted by the widely used V_peak model lack amplitudes at ≲1 h^-1 Mpc, suggesting that M_prog is a better proxy of the galaxy stellar mass than conventional V_peak. The z_prog parameter is highest (z_prog ≃ 3) for intermediate mass galaxies at M_* ≃ 10^9.9 h^-2 M_⊙, and becomes smaller down to z_prog ≃ 1 for both lower and higher mass galaxies. We interpret these trends as reflecting the downsizing in the in situ star formation in lower mass galaxies and the larger contribution of the ex situ stellar mass growth in higher mass galaxies.