Morphological properties of galaxies in different Local Volume environments

TL;DR

This study analyzes the properties of 1029 Local Volume galaxies, revealing how environment influences star formation and hydrogen content, with irregular and late-type galaxies showing sustained star formation, while quenched galaxies are more common in dense regions.

Contribution

It provides a comprehensive analysis of galaxy properties in the Local Volume, introducing environment metrics and examining their effects on star formation and gas content.

Findings

Star formation rate is more environment-sensitive than hydrogen mass fraction.

Most galaxies have low specific star-formation rates below -9.4 dex.

Quenched galaxies are more prevalent in dense environments.

Abstract

We consider an all-sky sample of 1029 Local Volume (LV) galaxies situated within a distance of 11 Mpc. Their majority have precise distances, estimates of hydrogen mass fraction and star-formation rate derived from far-ultraviolet or Halpha fluxes. To describe an environment, we attribute two dimensionless values: the density contrast created by the most significant neighbour and the local density contrast produced by all neighbours within a separation of 1 Mpc. The hydrogen mass fraction exhibits a weak effect of HI deficiency being the most pronounced for dwarf irregular galaxies. The specific star-formation rate (sSFR) is more sensitive to the environment than the hydrogen mass fraction. Almost all (99 per cent) LV galaxies have their sSFR below -9.4 dex (1/yr). We notice that irregular dwarfs as well as late-type bulgeless galaxies are capable to reproduce their stellar mass with the observed sSFR over the cosmic time. Thus, the transformation of gas into stars in dIrs and spiral disks is rather sluggish unlike that in E, S0, dSph galaxies, whose star-formation history has been stormy and short. Scatter of SFR(Halpha)-to-SFR(FUV) ratio increases from Sc, Sd, Sm galaxies towards BCD, Im, Ir types that favours the idea of bursty star formations in low-mass galaxies. However, this bursty activity is caused rather by internal processes than by an external tidal action. A fraction of quenched E, S0, dSph galaxies increases from ~5 per cent in the field up to ~50 per cent in the densest regions.