LESS THAN 10 PERCENT OF STAR FORMATION IN z approx 0.6 MASSIVE GALAXIES IS TRIGGERED BY MAJOR INTERACTIONS
- Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany)
- Department of Astronomy, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003 (United States)
- Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218 (United States)
- Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)
- Institute of Cosmology and Gravitation, University of Portsmouth, Hampshire Terrace, Portsmouth PO1 2EG (United Kingdom)
- Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada)
- Laboratoire d'Astrophysique, Ecole Polytechnique Federale de Lausanne (EPFL), Observatoire, CH-1290 Sauverny (Switzerland)
- Institute for Astro- and Particle Physics, University of Innsbruck, Technikerstr. 25/8, A-6020 Innsbruck (Austria)
- Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam (Germany)
- University of Texas, McDonald Observatory, Fort Davis, TX 79734 (United States)
- School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom)
- Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver V6T 1Z1 (Canada)
- Department of Astronomy, University of Texas at Austin, 1 University Station, C1400 Austin, TX 78712-0259 (United States)
Both observations and simulations show that major tidal interactions or mergers between gas-rich galaxies can lead to intense bursts of star formation. Yet, the average enhancement in star formation rate (SFR) in major mergers and the contribution of such events to the cosmic SFR are not well estimated. Here we use photometric redshifts, stellar masses, and UV SFRs from COMBO-17, 24 mum SFRs from Spitzer, and morphologies from two deep Hubble Space Telescope (HST) cosmological survey fields (ECDFS/GEMS and A901/STAGES) to study the enhancement in SFR as a function of projected galaxy separation. We apply two-point projected correlation function techniques, which we augment with morphologically selected very close pairs (separation <2'') and merger remnants from the HST imaging. Our analysis confirms that the most intensely star-forming systems are indeed interacting or merging. Yet, for massive (M{sub *} >= 10{sup 10} M{sub sun}) star-forming galaxies at 0.4 < z < 0.8, we find that the SFRs of galaxies undergoing a major interaction (mass ratios <=1:4 and separations <=40 kpc) are only 1.80 +- 0.30 times higher than the SFRs of non-interacting galaxies when averaged over all interactions and all stages of the interaction, in good agreement with other observational works. Our results also agree with hydrodynamical simulations of galaxy interactions, which produce some mergers with large bursts of star formation on approx100 Myr timescales, but only a modest SFR enhancement when averaged over the entire merger timescale. We demonstrate that these results imply that only approx<10% of star formation at 0.4 <= z <= 0.8 is triggered directly by major mergers and interactions; these events are not important factors in the build-up of stellar mass since z = 1.
- OSTI ID:
- 21367452
- Journal Information:
- Astrophysical Journal, Vol. 704, Issue 1; Other Information: DOI: 10.1088/0004-637X/704/1/324; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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