The Mass Dependence of Dwarf Satellite Galaxy Quenching

TL;DR

This study investigates how the fraction of quenched dwarf satellite galaxies varies with mass, revealing a sharp transition that constrains models of galaxy quenching mechanisms and timescales.

Contribution

It provides the first detailed analysis of mass-dependent quenching fractions in dwarf satellites, combining observations with models to understand quenching processes.

Findings

Low mass dwarfs are almost all quenched.

Quenched fraction decreases to 40-50% at higher masses.

Quenching occurs within 1-2 Gyr after pericenter for low mass satellites.

Abstract

We combine observations of the Local Group with data from the NASA-Sloan Atlas to show the variation in the quenched fraction of satellite galaxies from low mass dwarf spheroidals and dwarf irregulars to more massive dwarfs similar to the Magellanic clouds. While almost all of the low mass ($M_\star \lesssim 10^7$ $M_\odot$) dwarfs are quenched, at higher masses the quenched fraction decreases to approximately 40-50%. This change in the quenched fraction is large, and suggests a sudden change in the effectiveness of quenching that correlates with satellite mass. We combine this observation with models of satellite infall and ram pressure stripping to show that the low mass satellites must quench within 1-2 Gyr of pericenter passage to maintain a high quenched fraction, but that many more massive dwarfs must continue to form stars today even though they likely fell in to their host >5 Gyr ago. We also characterize how the susceptibility of dwarfs to ram pressure must vary as a function of mass if it is to account for the change in quenched fractions. Though neither model predicts the quenching effectiveness a priori, this modeling illustrates the physical requirements that the observed quenched fractions place on possible quenching mechanisms.