AKARI OBSERVATION OF THE NORTH ECLIPTIC POLE (NEP) SUPERCLUSTER AT z = 0.087: MID-INFRARED VIEW OF TRANSITION GALAXIES
- Yonsei University Observatory, Yonsei University, Seoul 120-749 (Korea, Republic of)
- Astronomy Program, Department of Physics and Astronomy, FPRD, Seoul National University, Seoul 151-742 (Korea, Republic of)
- Spitzer Science Center, California Institute of Technology, MS 220-6, Pasadena, CA 91125 (United States)
- Service d'Astrophysique, CEA Saclay, F-91191 Gif-sur-Yvette (France)
- Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)
- Department of Physics and Astronomy, University of California at Los Angeles, CA 90095 (United States)
- George P. and Cynthia W. Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics, Texas A and M University, College Station, TX 77843 (United States)
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Kanagawa 229-8510 (Japan)
- Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602 (Japan)
We present the mid-infrared (MIR) properties of galaxies within a supercluster in the north ecliptic pole region at z {approx} 0.087 observed with the AKARI satellite. We use data from the AKARI NEP-Wide (5.4 deg{sup 2}) IR survey and the CLusters of galaxies EVoLution studies (CLEVL) mission program. We show that near-IR (3 {mu}m)-mid-IR (11 {mu}m) color can be used as an indicator of the specific star formation rate and the presence of intermediate-age stellar populations. From the MIR observations, we find that red-sequence galaxies consist not only of passively evolving red early-type galaxies, but also of (1) 'weak-SFGs' (disk-dominated star-forming galaxies that have star formation rates lower by {approx}4 Multiplication-Sign than blue-cloud galaxies) and (2) 'intermediate-MXGs' (bulge-dominated galaxies showing stronger MIR dust emission than normal red early-type galaxies). These two populations can be a set of transition galaxies from blue, star-forming, late-type galaxies evolving into red, quiescent, early-type ones. We find that the weak-SFGs are predominant at intermediate masses (10{sup 10} M{sub Sun} < M{sub *} < 10{sup 10.5} M{sub Sun }) and are typically found in local densities similar to the outskirts of galaxy clusters. As much as 40% of the supercluster member galaxies in this mass range can be classified as weak-SFGs, but their proportion decreases to <10% at larger masses (M{sub *} > 10{sup 10.5} M{sub Sun }) at any galaxy density. The fraction of the intermediate-MXG among red-sequence galaxies at 10{sup 10} M{sub Sun} < M{sub *} < 10{sup 11} M{sub Sun} also decreases as the density and mass increase. In particular, {approx}42% of the red-sequence galaxies with early-type morphologies are classified as intermediate-MXGs at intermediate densities. These results suggest that the star formation activity is strongly dependent on the stellar mass, but that the morphological transformation is mainly controlled by the environment.
- OSTI ID:
- 22011700
- Journal Information:
- Astrophysical Journal, Vol. 745, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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