Dwarf Galaxies and the Cosmic Web

TL;DR

This paper proposes a new mechanism called cosmic web stripping, where ram-pressure from the cosmic web removes gas from low-mass halos, impacting dwarf galaxy formation and star formation histories.

Contribution

It introduces the concept of cosmic web stripping as a process affecting dwarf galaxies, based on cosmological simulations, adding a new perspective to galaxy formation models.

Findings

Gas removal from low-mass halos via ram-pressure

Impact on star formation histories of dwarf galaxies

Potential explanation for dwarf galaxy scarcity

Abstract

We use a cosmological simulation of the formation of the Local Group of Galaxies to identify a mechanism that enables the removal of baryons from low-mass halos without appealing to feedback or reionization. As the Local Group forms, matter bound to it develops a network of filaments and pancakes. This moving web of gas and dark matter drifts and sweeps a large volume, overtaking many halos in the process. The dark matter content of these halos is unaffected but their gas can be efficiently removed by ram-pressure. The loss of gas is especially pronounced in low-mass halos due to their lower binding energy and has a dramatic effect on the star formation history of affected systems. This "cosmic web stripping" may help to explain the scarcity of dwarf galaxies compared with the numerous low-mass halos expected in \Lambda CDM and the large diversity of star formation histories and morphologies characteristic of faint galaxies. Although our results are based on a single high-resolution simulation, it is likely that the hydrodynamical interaction of dwarf galaxies with the cosmic web is a crucial ingredient so far missing from galaxy formation models.