INTERACTING GALAXIES IN THE A901/902 SUPERCLUSTER WITH STAGES
- Department of Astronomy, University of Texas at Austin, 1 University Station C1400, Austin, TX 78712-0259 (United States)
- Institute for Astro- and Particle Physics, University of Innsbruck, Technikerstr. 25/8, A-6020 Innsbruck (Austria)
- NRC Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, V9E 2E7 (Canada)
- Scottish Universities Physics Alliance (SUPA), Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh, EH9 3HJ (United Kingdom)
- School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom)
- Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117, Heidelberg (Germany)
- Institute of Cosmology and Gravitation, Dennis Sciama Building, University of Portsmouth, Dennis Sciama Building, Portsmouth, PO1 3FX (United Kingdom)
- Department of Physics and Astronomy, University Of Waterloo, Waterloo, Ontario, N2L 3G1 (Canada)
- Laboratoire d'Astrophysique, Ecole Polytechnique Federalede Lausanne (EPFL), Observatoire, CH-1290 Sauverny (Switzerland)
- University of Texas, McDonald Observatory, Fort Davis, TX 79734 (United States)
- Department of Physics, 5110 Rockhill Road, University of Missouri-Kansas City, Kansas City, MO 64110 (United States)
- Centro Hispano Aleman de Calar Alto, C/Jesus Durban Remon 2-2, E-04004 Almeria (Spain)
We present a study of galaxy mergers and the influence of environment in the Abell 901/902 supercluster at zapprox 0.165, based on 893 bright (R{sub Vega}<= 24) intermediate-mass (M{sub *} >= 10{sup 9} M{sub sun}) galaxies. We use HST ACS F606W data from the Space Telescope A901/902 Galaxy Evolution Survey, COMBO-17, Spitzer 24 mum, and XMM-Newton X-ray data. Our analysis utilizes both a physically driven visual classification system and quantitative CAS parameters to identify systems which show evidence of a recent or ongoing merger of mass ratio >1/10 (i.e., major and minor mergers). Our results are (1) after visual classification and minimizing the contamination from false projection pairs, we find that the merger fraction f{sub merge} is 0.023 +- 0.007. The estimated fractions of likely major mergers, likely minor mergers, and ambiguous cases are 0.01 +- 0.004, 0.006 +- 0.003, and 0.007 +- 0.003, respectively. (2) All the mergers lie outside the cluster core of radius R< 0.25 Mpc: the lack of mergers in the core is likely due to the large galaxy velocity dispersion in the core. The mergers, instead, populate the region (0.25 Mpc <R<= 2 Mpc) between the core and the cluster outskirt. In this region, the estimated frequency of mergers is similar to those seen at typical group overdensities in N-body simulations of accreting groups in the A901/902 clusters. This suggests the ongoing growth of the clusters via accretion of group and field galaxies. (3) We compare our observed merger fraction with those reported in other clusters and groups out to zapprox 0.4. Existing data points on the merger fraction for L <= L* galaxies in clusters allow for a wide spectrum of scenarios, ranging from no evolution to evolution by a factor of approx5 over zapprox 0.17-0.4. (4) In A901/902, the fraction of interacting galaxies, which lie on the blue cloud is 80% +- 18% (16/20) versus 34% +- 7% or (294/866) for non-interacting galaxies, implying that interacting galaxies are preferentially blue. (5) The average star formation rate (SFR), based on UV or a combination of UV+IR data, is enhanced by a factor of approx1.5-2 in mergers compared to non-interacting galaxies. However, mergers in the A901/902 clusters contribute only a small fraction (between 10% and 15%) of the total SFR density, while the rest of the SFR density comes from non-interacting galaxies.
- OSTI ID:
- 21378280
- Journal Information:
- Astrophysical Journal, Vol. 705, Issue 2; Other Information: DOI: 10.1088/0004-637X/705/2/1433; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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