The Environmental Influence on the Evolution of Local Galaxies

TL;DR

This study investigates how the environment influences the evolution of dwarf galaxies by analyzing their star formation rates and gas content across different density regions, confirming environmental effects on galaxy morphology and activity.

Contribution

It provides new observational evidence linking galaxy environment to star formation and morphology, emphasizing the environmental impact on dwarf galaxy evolution.

Findings

Dwarf galaxies in high-density regions have lower current SFR.

Environmental factors correlate with galaxy morphology and gas content.

Dwarfs in denser environments show higher past average SFR.

Abstract

The results of an Halpha photometric survey of 30 dwarf galaxies of various morphologies in the Centaurus A and Sculptor groups are presented. Of these 30, emission was detected in 13: eight are of late-type, two are early-type and three are of mixed-morphology. The typical flux detection limit of 2e-16 erg s-1 cm-2, translates into a Star Formation Rate (SFR) detection limit of 4e-6 M_sol yr-1 . In the light of these results, the morphology-density relation is reexamined: It is shown that, despite a number of unaccounted parameters, there are significant correlations between the factors determining the morphological type of a galaxy and its environment. Dwarf galaxies in high density regions have lower current SFR and lower neutral gas content than their low density counterparts, confirming earlier results from the Local Group and other denser environments. The effect of environment is also seen in the timescale formed from the ratio of blue luminosity to current SFR - dwarfs in higher density environments have larger values, indicating relatively higher past average SFR. The influence of environment extends very far and no dwarfs from our sample can be identified as 'field' objects.