A Detection of the Environmental Dependence of the Sizes and Stellar Haloes of Massive Central Galaxies

TL;DR

This study uses deep imaging data from the HSC survey to demonstrate that the stellar profiles and outer stellar halos of massive central galaxies depend on their dark matter halo masses, revealing environmental effects on galaxy structure.

Contribution

It provides direct observational evidence linking halo mass to the size and stellar halo properties of massive galaxies without stacking, using unprecedented depth imaging.

Findings

Massive galaxies in more massive haloes have shallower inner profiles.

Outer stellar envelopes are more prominent in galaxies within larger haloes.

Halo mass influences the mass-size relation of central galaxies.

Abstract

We use ~100 square deg of deep (>28.5 mag arcsec$^{-2}$ in i-band), high-quality (median 0.6 arcsec seeing) imaging data from the Hyper Suprime-Cam (HSC) survey to reveal the halo mass dependence of the surface mass density profiles and outer stellar envelopes of massive galaxies. The i-band images from the HSC survey reach ~4 magnitudes deeper than Sloan Digital Sky Survey and enable us to directly trace stellar mass distributions to 100 kpc without requiring stacking. We conclusively show that, at fixed stellar mass, the stellar profiles of massive galaxies depend on the masses of their dark matter haloes. On average, massive central galaxies with $\log M_{\star, 100\ \mathrm{kpc}}>11.6$ in more massive haloes at 0.3 < z < 0.5 have shallower inner stellar mass density profiles (within ~10-20 kpc) and more prominent outer envelopes. These differences translate into a halo mass dependence of the mass-size relation. Central galaxies in haloes with $\log M_{\rm{Halo}}>14.0$ are ~20% larger in $R_{\mathrm{50}}$ at fixed stellar mass. Such dependence is also reflected in the relationship between the stellar mass within 10 and 100 kpc. Comparing to the mass--size relation, the $\log M_{\star, 100\ \rm{kpc}}$-$\log M_{\star, 10\ \rm{kpc}}$ relation avoids the ambiguity in the definition of size, and can be straightforwardly compared with simulations. Our results demonstrate that, with deep images from HSC, we can quantify the connection between halo mass and the outer stellar halo, which may provide new constraints on the formation and assembly of massive central galaxies.