Ko, Jongwan and Im, Myungshin and Lee, Hyung Mok and Lee, Myung Gyoon and Kim, Seong Jin and Shim, Hyunjin and Jeon, Yiseul and Hwang, Ho Seong and Willmer, Christopher N. A. and Malkan, Matthew A. and Papovich, Casey and Weiner, Benjamin J. and Matsuhara, Hideo and Oyabu, Shinki and Takagi, Toshinobu (2012) AKARI Observation of the North Ecliptic Pole (NEP) Supercluster at z = 0.087: Mid-infrared View of Transition Galaxies. Astrophysical Journal, 745 (2). Art. No. 181. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20120323-075031614
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We present the mid-infrared (MIR) properties of galaxies within a supercluster in the north ecliptic pole region at z ~ 0.087 observed with the AKARI satellite. We use data from the AKARI NEP-Wide (5.4 deg^2) IR survey and the CLusters of galaxies EVoLution studies (CLEVL) mission program. We show that near-IR (3 μm)-mid-IR (11 μm) 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 ~4 × 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^(10) M_☉ < M_* < 10^(10.5) M_☉) 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_* > 10^(10.5) M_☉) at any galaxy density. The fraction of the intermediate-MXG among red-sequence galaxies at 10^(10) M_☉ < M_* < 10^(11) M_☉ also decreases as the density and mass increase. In particular, ~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.
|Additional Information:||© 2012 American Astronomical Society. Received 2011 September 9; accepted 2011 November 28; published 2012 January 17. This work is based on observations with AKARI, a JAXA project with the participation of ESA. This work was supported by the Korea Science and Engineering Foundation (KOSEF) grant no. 2009-0063616, funded by the Korea government (MEST). J.K. was supported by “KASI–Yonsei Joint Research for the Frontiers of Astronomy and Space Science” program (2011) funded by Korea Astronomy and Space Science Institute. We thank L. Piovan for providing his SED model, and Stephane Charlot and Gustavo Bruzual for kindly sending us the new version of their CB07 model. H.S.H. acknowledges the support of the Centre National d’Etudes Spatiales (CNES). This work is partly based on observations obtained with the MMT, a joint facility operated by the Smithsonian Astrophysical Observatory and the University of Arizona, and with the telescopes at the Kitt Peak National Observatory. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.|
|Subject Keywords:||galaxies: clusters: general; galaxies: evolution; galaxies: stellar content; infrared: galaxies; surveys|
|Official Citation:||AKARI Observation of the North Ecliptic Pole (NEP) Supercluster at z = 0.087: Mid-infrared View of Transition Galaxies Jongwan Ko et al. 2012 ApJ 745 181|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||23 Mar 2012 15:27|
|Last Modified:||26 Dec 2012 14:58|
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