Interaction-induced star formation in a complete sample of 105 nearby star-forming galaxies |
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| Authors: | Cheng Li Guinevere Kauffmann Timothy M Heckman Y P Jing Simon D M White |
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| Institution: | MPA/SHAO Joint Centre for Astrophysical Cosmology at Shanghai Astronomical Observatory, Nandan Road 80, Shanghai 200030, China;Max Planck Institut für Astrophysik, Karl-Schwarzschild-Strasse 1, 85748 Garching, Germany;Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA |
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| Abstract: | We investigate the clustering properties of a complete sample of 105 star-forming galaxies drawn from the data release 4 (DR4) of the Sloan Digital Sky Survey. On scales less than 100 kpc, the amplitude of the correlation function exhibits a strong dependence on the specific star formation rate (SSFR) of the galaxy. We interpret this as the signature of enhanced star formation induced by tidal interactions. We then explore how the average star formation rate (SFR) in a galaxy is enhanced as the projected separation r p between the galaxy and its companions decreases. We find that the enhancement strongly depends on r p, but very weakly on the relative luminosity of the companions. The enhancement is also stronger in low-mass galaxies than in high-mass galaxies. In order to explore whether a tidal interaction is not only sufficient, but also necessary to trigger enhanced star formation in a galaxy, we compute background subtracted neighbour counts for the galaxies in our sample. The average number of close neighbours around galaxies with low to average values of SFR/ M * is close to zero. At the highest SSFRs, however, more than 40 per cent of the galaxies in our sample have a companion within a projected radius of 100 kpc. Visual inspection of the highest SFR/ M * galaxies without companions reveals that more than 50 per cent of these are clear interacting or merging systems. We conclude that tidal interactions are the dominant trigger of enhanced star formation in the most strongly star-forming systems. Finally, we find clear evidence that tidal interactions not only lead to enhanced star formation in galaxies, but also cause structural changes such as an increase in concentration. |
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| Keywords: | galaxies: clusters: general galaxies: distances and redshifts cosmology: theory dark matter large-scale structure of Universe |
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