Insights about the Assembly of Massive Central Galaxies using Hyper Suprime-Cam

Predicted by the promising hierarchical formation model, the stellar halos of massive galaxies should keep vital fossil records regarding their assembly history and galaxy-halo connection.  However, due to its low surface brightness, much of this information is yet to be understood.   Using the deep i-band images from the Subaru Hyper Suprime-Cam (HSC) survey, we map the stellar mass distributions for a large sample of massive galaxies (log M*>11.6 Msun) out to more than 100 kpc individually, and reveal the interesting structural diversity in their stellar halos.  We find that both the slopes of the mass density profiles and the shapes of the stellar halos depend on total stellar mass: more massive galaxies on average host more extended halos with shallower slope and more elongated shape.  We also discover subtle, but systematic structural differences that depend on halo mass: central galaxy from more massive halo has on average larger size than the one in less massive halo at fixed stellar mass.  We have confirmed this trend using weak lensing measurements from HSC.  We will also discuss these results from the perspective of their assembly history.

Speaker: Song Huang, UC Santa Cruz