Star Formation Density and Halpha Luminosity Function of an Emission Line Selected Galaxy Sample at z ~ 0.24

TL;DR

This study measures the Halpha luminosity function and star formation density at z ~ 0.24 using narrowband imaging, revealing environmental influences on star formation rates and highlighting uncertainties in luminosity function comparisons.

Contribution

It provides new measurements of the Halpha luminosity function at z ~ 0.24 with detailed correction methods and compares results across different fields and surveys, emphasizing systematic uncertainties.

Findings

Field samples differ in faint end slope and luminosity.

Sample has a fainter L* turn-over compared to other surveys.

Star formation rate increases with local galaxy density.

Abstract

We use narrowband imaging (FWHM = 70 A) to select a sample of emission line galaxies between 0.20 <~ z <~ 1.22 in two fields covering 0.5 sq. deg. We use spectroscopic follow-up to select a sub-sample of Halpha emitting galaxies at z ~ 0.24 and determine the Halpha luminosity function and star formation density at z ~ 0.24 for both of our fields. Corrections are made for imaging and spectroscopic incompleteness, extinction and interloper contamination on the basis of the spectroscopic data. When compared to each other, we find the field samples differ by \Delta \alpha = 0.2 in faint end slope and \Delta \log [ L* (ergs/s) ] = 0.2 in luminosity. In the context of other recent surveys, our sample has comparable faint end slope, but a fainter L* turn-over. We conclude that systematic uncertainties and differences in selection criteria remain the dominant sources of uncertainty between Halpha luminosity functions at this redshift. We also investigate average star formation rates as a function of local environment and find typical values consistent with the field densities that we probe, in agreement with previous results. However, we find tentative evidence for an increase in star formation rate with respect to the local density of star forming galaxies, consistent with the scenario that galaxy-galaxy interactions are triggers for bursts of star formation.