The quenching of star formation in dwarf galaxies: new perspectives from deep-wide surveys

TL;DR

This study uses deep, wide-field surveys to analyze the quenching of star formation in dwarf galaxies, revealing that both environmental factors and internal processes contribute to galaxy evolution.

Contribution

It provides an unbiased statistical analysis of ~7,000 dwarf galaxies at low redshift, highlighting the roles of environment and internal feedback in star formation quenching.

Findings

Approximately 40% of dwarfs are red/quenched at z~0.05

Proximity to massive galaxies influences quenching more than local density

About half of red dwarfs are quenched by internal processes

Abstract

Dwarf galaxies dominate the galaxy number density, making them critical to our understanding of galaxy evolution. However, typical dwarfs are too faint to be visible outside the very local Universe in past surveys like the SDSS, which offer large footprints but are shallow. Dwarfs in such surveys have relatively high star formation rates, which boost their luminosity, making them detectable in shallow surveys, but also biased and potentially unrepresentative of dwarfs as a whole. Here, we use deep data to perform an unbiased statistical study of ~7,000 nearby (z<0.25) dwarfs (10^8 MSun < M < 10^9.5 MSun) in the COSMOS field which, at these redshifts, is a relatively low-density field. At z~0.05, ~40 per cent of dwarfs in low-density environments are red/quenched, falling to ~30 per cent by z~0.25. Red dwarfs reside closer to nodes, filaments and massive galaxies. Proximity to a massive galaxy appears to be more important in determining whether a dwarf is red, rather than simply its distance from nodes and filaments or the mean density of its local environment. Interestingly, around half of the red dwarfs reside outside the virial radii of massive galaxies and around a third of those also inhabit regions in the lower 50 per cent in density percentile (i.e. regions of very low ambient density). Around half of the red dwarf population is, therefore, quenched by mechanisms unrelated to environment, which are likely to be internal processes such as stellar and AGN feedback.