Evolution of the Halpha luminosity function

TL;DR

This study analyzes the evolution of the Halpha luminosity function over the last 4 Gyr, revealing that the characteristic luminosity increases and star formation activity is often triggered by galaxy interactions.

Contribution

It provides the first large-volume measurement of the Halpha luminosity function at z ~ 0.24, showing evolution in L* and star formation density with implications for galaxy interaction effects.

Findings

L* increases by 0.84 dex from z=0.1 to 0.377

Star formation density increases by 0.11 dex

Higher fraction of galaxies with close neighbors at higher L(Halpha)

Abstract

The Smithsonian Hectospec Lensing Survey (SHELS) is a window on the star formation history over the last 4 Gyr. SHELS is a spectroscopically complete survey for Rtot < 20.3 over 4 square degrees. We use the 10k spectra to select a sample of pure star forming galaxies based on their Halpha emission line. We use the spectroscopy to determine extinction corrections for individual galaxies and to remove active galaxies in order to reduce systematic uncertainties. We use the large volume of SHELS with the depth of a narrowband survey for Halpha galaxies at z ~ 0.24 to make a combined determination of the Halpha luminosity function at z ~ 0.24. The large area covered by SHELS yields a survey volume big enough to determine the bright end of the Halpha luminosity function from redshift 0.100 to 0.377 for an assumed fixed faint-end slope alpha = -1.20. The bright end evolves: the characteristic luminosity L* increases by 0.84 dex over this redshift range. Similarly, the star formation density increases by 0.11 dex. The fraction of galaxies with a close neighbor increases by a factor of 2-5 for L(Halpha) >~ L* in each of the redshift bins. We conclude that triggered star formation is an important influence for star forming galaxies with Halpha emission.