The Nun Path: The Evolution and Quenching of Satellite Galaxies

TL;DR

This paper investigates the quenching process of satellite galaxies using cosmological simulations, identifying key phases and drivers, and introduces new methods and findings related to galaxy evolution and structure.

Contribution

It provides a detailed analysis of satellite galaxy quenching, introduces an innovative merger tree construction method, and reports new findings on dark matter decoupling and compact elliptical galaxy formation.

Findings

Quenching involves three phases: gas accretion halt, rapid sSFR drop, and stellar heating/stripping.

Ram pressure and tidal forces are primary drivers of quenching, with secondary roles for star formation and feedback.

Decoupling of dark matter from stellar components and formation of compact elliptical satellites are newly identified phenomena.

Abstract

The galaxy quenching process, in which a galaxy stops forming stars is a crucial stage in galaxy life. Two mechanisms for quenching are possible: halo mass quenching of central galaxies and environmental quenching of satellite galaxies. This thesis describes the satellite galaxies (SG) quenching process and its primary causes. The analysis contains a study of a large sample of 118 SGs within the Vela cosmological simulation, identified by a specific SG merger tree algorithm. We find that the quenching evolves through a typical path in the diagram of specific star formation (sSFR) vs. inner stellar surface density ($\Sigma_{\star, 0.5\textrm kpc}$), with the inner surface density defined as the density within 0.5kpc from the center of mass of the SG. Three discrete phases characterize this path: 1. Halt in gas accretion with SG compaction at high sSFR as the SG keeps forming stars 2. Gas removal and rapid drop in the sSFR at the peri-center of its orbit within the host halo 3. Stellar heating and stripping may lead to coalescing with the halo center, an ultra-diffuse galaxy (UDG), a compact elliptical galaxy (eCg), or a globular cluster (GC). We find that the main drivers of SG evolution are ram pressure stripping at the initial stages and tidal forces at the final stages, aided by starvation, suppression of gas accretion. We show that other processes, such as gas depletion by star formation or stellar feedback are secondary. Moreover, we present an innovative method for constructing merger trees in simulations that solve systemic errors. Two new significant results presented here: a. Decoupling of dark-matter from the stellar component in SGs. b. Compact elliptical SG formation. An assembly of these results and others are presented in a fast and robust catalog.