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Abstract: We analyse Spitzer MIPS 24micron observations, and SDSS DR7 opticalbroadband photometry and spectra, to investigate the star formation SFproperties of galaxies residing in the Coma supercluster region. We find thatSF in dwarf galaxies is quenched only in the high density environment at thecentre of clusters and groups, but passively-evolving massive galaxies arefound in all environments, indicating that massive galaxies can become passivevia internal processes. We find AGN activity is suppressed in the clustercores. We present evidence for a strong dependence of the mechanismsresponsible for quenching SF in dwarf galaxies on the cluster potential. Wefind a significant increase in the mean EW of Halpha among star-forming dwarfgalaxies in the infall regions of the Coma cluster and the core of Abell 1367with respect to the overall supercluster population, indicative of theinfalling dwarf galaxies undergoing a starburst phase. We identify thesestarburst galaxies as the precursors of the post-starburst k+A galaxies. Wefind that 11.4% of all dwarf z mag > 15 galaxies in the Coma cluster and 4.8%in the Abell 1367 have k+A like spectra, while this fraction is just 2.1% whenaveraged over the entire supercluster region. We show that in the centre of theComa cluster, the 24-z colour of galaxies is correlated with their opticalg-r colour and Halpha emission. By analysing the projected phase spacedistribution of galaxies detected at 24micron in Coma, we find that theoptically red 24 micron detected galaxies follow the general distribution of`all- the spectroscopic members, but their optically blue counterparts showinteresting features, indicative of recent infall.



Author: Smriti Mahajan, Chris P. Haines, Somak Raychaudhury

Source: https://arxiv.org/







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