A Deep Halpha Survey of Galaxies in the Two Nearby Clusters Abell1367 and Coma: The Halpha Luminosity Functions

TL;DR

This study conducts a deep Halpha imaging survey of the Coma and Abell1367 galaxy clusters, determining their Halpha luminosity functions and comparing them with field galaxies to understand star formation contributions.

Contribution

First measurement of Schechter parameters for cluster galaxy Halpha luminosity functions using deep wide-field imaging.

Findings

Cluster Halpha LFs have flatter slopes than field galaxies.

Clusters contribute about 0.25% to the local Universe's star formation rate.

Cluster LFs show lower characteristic luminosities than field galaxy LFs.

Abstract

We present a deep wide field Halpha imaging survey of the central regions of the two nearby clusters of galaxies Coma and Abell1367, taken with the WFC at the INT2.5m telescope. We determine for the first time the Schechter parameters of the Halpha luminosity function (LF) of cluster galaxies. The Halpha LFs of Abell1367 and Coma are compared with each other and with that of Virgo, estimated using the B band LF by Sandage et al. (1985) and a L(Halpha) vs M_B relation. Typical parameters of phi^* ~ 10^0.00+-0.07 Mpc^-3, L^* ~ 10^41.25+- 0.05 erg sec^-1 and alpha ~ -0.70+-0.10 are found for the three clusters. The best fitting parameters of the cluster LFs differ from those found for field galaxies, showing flatter slopes and lower scaling luminosities L^*. Since, however, our Halpha survey is significantly deeper than those of field galaxies, this result must be confirmed on similarly deep measurements of field galaxies. By computing the total SFR per unit volume of cluster galaxies, and taking into account the cluster density in the local Universe, we estimate that the contribution of clusters like Coma and Abell1367 is approximately 0.25% of the SFR per unit volume of the local Universe.