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Enhanced Warm H_2 Emission in the Compact Group Mid-infrared "Green Valley"

Cluver, M. E. and Appleton, P. N. and Ogle, P. and Jarrett, T. H. and Rasmussen, J. and Lisenfeld, U. and Guillard, P. and Verdes-Montenegro, L. and Antonucci, R. and Bitsakis, T. and Charmandaris, V. and Boulanger, F. and Egami, E. and Xu, C. K. and Yun, M. S. (2013) Enhanced Warm H_2 Emission in the Compact Group Mid-infrared "Green Valley". Astrophysical Journal, 765 (2). Art. No. 93. ISSN 0004-637X. doi:10.1088/0004-637X/765/2/93.

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We present results from a Spitzer mid-infrared spectroscopy study of a sample of 74 galaxies located in 23 Hickson Compact Groups (HCGs), chosen to be at a dynamically active stage of H I depletion. We find evidence for enhanced warm H_2 emission (i.e., above that associated with UV excitation in star-forming regions) in 14 galaxies (~20%), with 8 galaxies having extreme values of L(H_2 S(0)-S(3))/L(7.7 μm polycyclic aromatic hydrocarbon), in excess of 0.07. Such emission has been seen previously in the compact group HCG 92 (Stephan's Quintet), and was shown to be associated with the dissipation of mechanical energy associated with a large-scale shock caused when one group member collided, at high velocity, with tidal debris in the intragroup medium. Similarly, shock excitation or turbulent heating is likely responsible for the enhanced H_2 emission in the compact group galaxies, since other sources of heating (UV or X-ray excitation from star formation or active galactic nuclei) are insufficient to account for the observed emission. The group galaxies fall predominantly in a region of mid-infrared color-color space identified by previous studies as being connected to rapid transformations in HCG galaxy evolution. Furthermore, the majority of H_2-enhanced galaxies lie in the optical "green valley" between the blue cloud and red sequence, and are primarily early-type disk systems. We suggest that H2-enhanced systems may represent a specific phase in the evolution of galaxies in dense environments and provide new insight into mechanisms which transform galaxies onto the optical red sequence.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Cluver, M. E.0000-0002-9871-6490
Appleton, P. N.0000-0002-7607-8766
Ogle, P.0000-0002-3471-981X
Jarrett, T. H.0000-0002-4939-734X
Lisenfeld, U.0000-0002-9471-5423
Guillard, P.0000-0002-2421-1350
Bitsakis, T.0000-0001-5787-8242
Charmandaris, V.0000-0002-2688-1956
Xu, C. K.0000-0002-1588-6700
Yun, M. S.0000-0001-7095-7543
Additional Information:© 2013 American Astronomical Society. Received 2012 July 6; accepted 2013 January 17; published 2013 February 20. thank the referee for helpful comments and suggestions that improved the content and clarity of this paper. We are grateful to Sanch Borthakur (Johns Hopkins University) for access to unpublished Hi data and Michael Brown (Monash University) for the use of his galaxy template library. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407. M.E.C. acknowledges support from the Australian Research Council (FS110200023). Support for this work was provided by NASA through an award issued by JPL/Caltech. U.L. acknowledges support by the research projects AYA2007-67625-C02-02 and AYA2011-24728 from the Spanish Ministerio de Ciencia y Educaciόn and the Junta de Andalucía (Spain) grant FQM108. L.V.M. is funded by grants AYA2008-06181-C02 and AYA2011-30491-C02-01, co-financed by MICINN and FEDER funds, and the Junta de Andalucía (Spain) grants P08-FQM-4205 and TIC-114. 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. This research has made use of data obtained from the Chandra Source Catalog, provided by the Chandra X-ray Center (CXC) as part of the Chandra Data Archive.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Australian Research CouncilFS110200023
Ministerio de Ciencia y Educaciόn (MEC)AYA2007-67625-C02-02
Ministerio de Ciencia y Educaciόn (MEC)AYA2011-24728
Junta de AndalucíaFQM108
Ministerio de Ciencia e Innovación (MCINN)AYA2008-06181-C02
Ministerio de Ciencia e Innovación (MCINN)AYA2011-30491-C02-01
Junta de AndalucíaP08-FQM-4205
Junta de AndalucíaTIC-114
Fondo Europeo de Desarrollo Regional (FEDER)UNSPECIFIED
Subject Keywords:galaxies: evolution; galaxies: groups: general; galaxies: interactions; galaxies: ISM; infrared: galaxies; intergalactic medium
Issue or Number:2
Record Number:CaltechAUTHORS:20130408-071054973
Persistent URL:
Official Citation:Enhanced Warm H2 Emission in the Compact Group Mid-infrared "Green Valley" M. E. Cluver et al. 2013 ApJ 765 93
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37794
Deposited By: Ruth Sustaita
Deposited On:08 Apr 2013 14:57
Last Modified:09 Nov 2021 23:31

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