Environmental effects in galaxies: Molecular Gas, Star Formation, and Activity

Abstract

In order to study whether there is any correlation between nuclear activities, gas content, and the environment where galaxies reside, we have obtained optical and millimetric spectra for a well-defined sample of intermediate Hubble type spirals in dense environments and in the field. We found that these spirals in dense environments have on average: less molecular gas per blue luminosity, higher atomic gas fraction, lower current star formation rate, and the same star formation efficiency as field galaxies. Although none of these results stand out as a single strong diagnostic, given their statistical significance, taken together they indicate a trend for diminished gas content and star formation activity in galaxies in high density environments. Our results suggest that galaxies in dense environments have either (i) consumed their molecular gas via star formation in the past or (ii) that dense environments leads to an inhibition of molecular gas from atomic phase. The similarities in star formation efficiency of the dense environments and field galaxies suggest that the physical processes controling the formation of stars from the molecular gas are local rather than global. We also found that star formation rate per blue luminosity increases linearly as the total amount of gas increases in LINERs. This result, based on a small sample, suggests that LINERs are powered by star formation rather than an AGN.

12 pages, 12 figures, A&A accepted

References in corpus (4)

• Tidally-Triggered Star Formation in Close Pairs of Galaxies
• The Nature of LINERs
• The Relation Between Activity and Environment in Compact Groups of Galaxies
• Environmental Effects in Galaxies: The Data

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• The Fornax Deep Survey with VST. X. The assembly history of the bright galaxies and intra-group light in the Fornax A subgroup
• Ionised carbon and galaxy activity
• Stochastic processes, galactic star formation, and chemical evolution. Effects of accretion, stripping, and collisions in multiphase multi-zone models
• Environmental Effects in Galaxies: The Data
• Galaxies with unusually high abundances of molecular hydrogen