The hidden satellites of massive galaxies and quasars at high-redshift

TL;DR

This study uses advanced simulations to show that stellar radiative feedback and tidal forces significantly influence the number and properties of satellite galaxies around massive high-redshift galaxies and quasars.

Contribution

It demonstrates how stellar radiative feedback affects satellite survival and galaxy size, providing new insights into galaxy evolution in the early universe.

Findings

Radiative feedback reduces satellite counts by up to 60%.

Satellites are more vulnerable to tidal disruption due to weaker binding.

Central galaxy size increases by up to a factor of 3.

Abstract

Using cosmological, radiation-hydrodynamic simulations targeting a rare $\approx \, 2 \times 10^{12} \, \rm M_\odot$ halo at $z \, = \, 6$, we show that the number counts and internal properties of satellite galaxies within the massive halo are sensitively regulated by a combination of local stellar radiative feedback and strong tidal forces. Radiative feedback operates before the first supernova explosions erupt and results in less tightly-bound galaxies. Satellites are therefore more vulnerable to tidal stripping when they accrete onto the main progenitor and are tidally disrupted on a significantly shorter timescale. Consequently, the number of satellites with $M_{\rm \star} > 10^{7} \, \rm M_\odot$ within the parent system's virial radius drops by up to $60 \%$ with respect to an identical simulation performed without stellar radiative feedback. Radiative feedback also impacts the central galaxy, whose effective radius increases by a factor $\lesssim 3$ due to the presence of a more extended and diffuse stellar component. We suggest that the number of satellites in the vicinity of massive high-redshift galaxies is an indication of the strength of stellar radiative feedback and and can be anomalously low in the extreme cosmic environments of high-redshift quasars.