OMEGA -- OSIRIS Mapping of Emission-line Galaxies in A901/2: II. -- Environmental influence on integrated star formation properties and AGN activity

Abstract

We present a study of the star formation and AGN activity for galaxies in the Abell 901/2 multi-cluster system at z~0.167 as part of the OMEGA survey. Using Tuneable Filter data obtained with the OSIRIS instrument at the GTC we produce spectra covering the Halpha and [N II] spectral lines for more than 400 galaxies. Using optical emission-line diagnostics, we identify a significant number of galaxies hosting AGN, which tend to have high masses and a broad range of morphologies. Moreover, within the environmental densities probed by our study, we find no environmental dependence on the fraction of galaxies hosting AGN. The analysis of the integrated Halpha emission shows that the specific star formation rates (SSFRs) of a majority of the cluster galaxies are below the field values for a given stellar mass. We interpret this result as evidence for a slow decrease in the star formation activity of star-forming galaxies as they fall into higher-density regions, contrary to some previous studies which suggested a rapid truncation of star formation. We find that most of the intermediate- and high-mass spiral galaxies go through a phase in which their star formation is suppressed but still retain significant star-formation activity. During this phase, these galaxies tend to retain their spiral morphology while their colours become redder. The presence of this type of galaxies in high density regions indicates that the physical mechanism responsible for suppressing star-formation affects mainly the gas component of the galaxies, suggesting that ram-pressure stripping or starvation are potentially responsible.

20 pages, 16 figures. Accepted for publication in MNRAS

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• Exploring the AGN-ram pressure stripping connection in local clusters
• NoSOCS in SDSS. VI. The Environmental Dependence of AGN in Clusters and Field in the Local Universe
• SDSS-IV MaNGA: spatially resolved dust attenuation in spiral galaxies
• Galaxy cluster mergers as triggers for the formation of jellyfish galaxies: case study of the A901/2 system
• OMEGA - OSIRIS Mapping of Emission-line Galaxies in A901/2: III. - Galaxy Properties Across Projected Phase Space in A901/2
• The Local Cluster Survey II: Disk-Dominated Cluster Galaxies with Suppressed Star Formation
• The effect of the environment on the structure, morphology and star-formation history of intermediate-redshift galaxies
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• Investigating the Impacts of AGN Activities on Dwarf Galaxies with FAST HI Observations