Galaxy And Mass Assembly (GAMA): Galaxies at the faint end of the Halpha luminosity function

TL;DR

This study analyzes the faintest Halpha-emitting galaxies in the GAMA survey, revealing they are mostly low-mass, star-forming systems located in low-density environments, with diverse star formation histories.

Contribution

It provides new insights into the properties and environments of the lowest Halpha-luminosity galaxies, highlighting their low mass, isolated nature, and varied star formation histories.

Findings

Most are low-mass systems with median stellar mass 2.5x10^8 Msun.

They predominantly reside in low-density environments (~0.02 galaxy Mpc^-2).

Their specific star formation rates indicate diverse star formation histories.

Abstract

We present an analysis of the properties of the lowest Halpha-luminosity galaxies (L_Halpha<4x10^32 W; SFR<0.02 Msun/yr) in the Galaxy And Mass Assembly (GAMA) survey. These galaxies make up the the rise above a Schechter function in the number density of systems seen at the faint end of the Halpha luminosity function. Above our flux limit we find that these galaxies are principally composed of intrinsically low stellar mass systems (median stellar mass =2.5x10^8 Msun) with only 5/90 having stellar masses M>10^10 Msun. The low SFR systems are found to exist predominantly in the lowest density environments (median density ~0.02 galaxy Mpc^-2 with none in environments more dense than ~1.5 galaxy Mpc^-2). Their current specific star formation rates (SSFR; -8.5 < log(SSFR[yr^-1])<-12.) are consistent with their having had a variety of star formation histories. The low density environments of these galaxies demonstrates that such low-mass, star-forming systems can only remain as low-mass and forming stars if they reside sufficiently far from other galaxies to avoid being accreted, dispersed through tidal effects or having their gas reservoirs rendered ineffective through external processes.