Star forming galaxies in the Hercules cluster: Halpha imaging of A2151

TL;DR

This study investigates star formation in galaxies within the Hercules cluster A2151 using Halpha imaging, revealing environmental effects on star formation rates and galaxy morphology compared to other clusters and field galaxies.

Contribution

First Halpha imaging survey of A2151, demonstrating environmental influences on galaxy star formation and morphology within the cluster.

Findings

Cluster galaxies show lower Halpha luminosity than expected for their brightness.

Differences in Halpha properties between cluster and field galaxies.

Cluster environment and merging history affect star formation activity.

Abstract

This paper presents the first results of an Halpha imaging survey of galaxies in the central regions of the A2151 cluster. A total of 50 sources were detected in Halpha. The morphologies of the 43 H$\alpha$ selected galaxies range from grand design spirals and interacting galaxies to blue compacts and tidal dwarfs or isolated extragalactic HII regions, spanning a range of magnitudes of -21 <= MB <= -12.5 mag. A comparison with the clusters Coma and A1367 and a sample of field galaxies has shown the presence of cluster galaxies with L(Halpha) lower than expected for their MB, a consecuence of the cluster environment. This fact results in differences in the L(Halpha) vs. EW(Halpha) and L(H\alpha) distributions of the clusters with respect to the field, and in cluster to cluster variations of these quantities, which we propose are driven by a global cluster property as the total mass. Overall, we conclude that both, the global cluster environment as well as the cluster merging history play a non negligible role in the integral star formation properties of clusters of galaxies.