Abstract
We study how interactions between galaxies affect star formation within them by considering a sample of almost 1500 of the nearest galaxies, all within a distance of ∼45 Mpc. We use the far-IR emission to define the massive star formation rate (SFR), and then normalise the SFR by the stellar mass of the galaxy to obtain the specific star formation rate (SSFR). We explore the distribution of (S)SFR with morphological type and with stellar mass. We calculate the relative enhancement of SFR and SSFR for each galaxy by normalising them by the median SFR and SSFR values of individual control samples of similar non-interacting galaxies. We find that both the median SFR and SSFR are enhanced in interacting galaxies, and more so as the degree of interaction is higher. The increase is moderate, reaching a maximum of a factor of 1.9 for the highest degree of interaction (mergers). While the SFR and SSFR are enhanced statistically by interactions, in many individual interacting galaxies they are not enhanced at all. Our study is based on a representative sample of nearby galaxies and should be used to place constraints on studies based on samples of galaxies at larger distances.
Highlights
Galaxy-galaxy interactions and mergers are an important factor in the dominant cosmological model of galaxy evolution, in which mergers between dark matter haloes and/or luminous galaxies occur frequently, increasing their mass and shaping them into the galaxies that we observe at the current epoch
We summarise here the results of our statistical study of the star formation rate (SFR) and the specific SFR (SSFR; SFR normalised by stellar mass) of a sample of some 1500 galaxies in the very local Universe, within a distance of ∼45 Mpc ([7,10])
Using a sample of 1500 nearby galaxies from the S4 G we quantify the role of galaxy-galaxy interactions in enhancing the star formation
Summary
Galaxy-galaxy interactions and mergers are an important factor in the dominant cosmological model of galaxy evolution, in which mergers between dark matter haloes and/or luminous galaxies occur frequently, increasing their mass and shaping them into the galaxies that we observe at the current epoch. We summarise here the results of our statistical study of the SFR and the specific SFR (SSFR; SFR normalised by stellar mass) of a sample of some 1500 galaxies in the very local Universe, within a distance of ∼45 Mpc ([7,10]). This sample is unique because it covers galaxies down to stellar masses of around 108 M and of all morphological types, and should be considered as a local analogue for studies of galaxies at higher redshifts
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