The Environmental Quenching Mechanisms of Field Dwarf Galaxies

TL;DR

This study uses the TNG50 simulation to show that environmental effects like cosmic web stripping and backsplash phenomena are primary mechanisms quenching star formation in field dwarf galaxies, especially at lower stellar masses.

Contribution

It identifies and characterizes the environmental processes responsible for quenching in isolated field dwarf galaxies, highlighting the role of cosmic web stripping and backsplash effects.

Findings

Quenched fraction increases with decreasing stellar mass.

Most isolated quenched dwarfs are affected by the cosmic web.

Backsplash dwarfs are more dark matter deficient and stopped forming stars earlier.

Abstract

Field dwarf galaxies not actively forming stars are relatively rare in the local Universe, but are present in cosmological hydrodynamical simulations. We use the TNG50 simulation to investigate their origin and find that they all result from environmental effects that have removed or reduced their gas content. Quenched field dwarfs consist of either backsplash objects ejected from a massive host or of systems that have lost their gas after crossing overdense regions such as filaments or sheets (``cosmic web stripping''). Quenched fractions rise steeply with decreasing stellar mass, with quenched systems making up roughly $\sim 15\%$ of all field dwarfs (i.e., excluding satellites) with stellar masses $10^{7}<M_{\star}/M_{\odot}<10^{9}$. This fraction drops to only $\sim1\%$ when a strict isolation criterion that requires no neighbours with $M_{\star}>10^9\, M_{\odot}$ within {$1.5$} Mpc is applied. Of these isolated dwarfs, $\sim 6\%$ are backsplash, while the other $\sim 94\%$ have been affected by the cosmic web. Backsplash systems are more deficient in dark matter, have retained less or no gas, and have stopped forming stars earlier than cosmic web-stripped systems. The discovery of deeply isolated dwarf galaxies which were quenched relatively recently would lend observational support to the prediction that the cosmic web is capable of inducing the cessation of star formation in dwarfs.