A Large Mass of H_2 in the Brightest Cluster Galaxy in Zwicky 3146

Creators: Egami, E.; Rieke, G. H.; Fadda, D.; Hines, D. C.

Abstract

We present the Spitzer/IRS mid-infrared spectrum of the infrared-luminous (L_(IR) = 4 × 10^(11) L_☉) brightest cluster galaxy (BCG) in the X-ray-luminous cluster Zwicky 3146 (Z3146; z = 0.29). The spectrum shows strong aromatic emission features, indicating that the dominant source of the infrared luminosity is star formation. The most striking feature of the spectrum, however, is the exceptionally strong molecular hydrogen (H_2) emission lines, which seem to be shock-excited. The line luminosities and inferred warm H_2 gas mass (~10^(10) M_☉) are 6 times larger than those of NGC 6240, the most H_2-luminous galaxy at z ≲ 0.05. Together with the large amount of cold H_2 detected previously (~10^(11) M_☉), this indicates that the Z3146 BCG contains disproportionately large amounts of both warm and cold H_2 gas for its infrared luminosity, which may be related to the intracluster gas cooling process in the cluster core.

Additional Information

© 2006 American Astronomical Society. Received 2006 August 4; accepted 2006 October 5; published 2006 October 30. We would like to thank G. Neugebauer and the anonymous referee for their comments, which improved the Letter. 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 a contract with NASA (contract 1407). Support for this work was provided by NASA through an award issued by JPL/Caltech (contract 1255094).

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