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Why are some brightest cluster galaxies forming stars?

Published online by Cambridge University Press:  01 July 2007

Christopher P. O'Dea
Affiliation:
Department of Physics, Rochester Institute of Technology, Rochester, NY 14623, USA email: [email protected]
Alice Quillen
Affiliation:
Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627, USA email: [email protected]
Nicholas Zufelt
Affiliation:
Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627, USA email: [email protected]
Jaehong Park
Affiliation:
Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627, USA email: [email protected]
Alastair Edge
Affiliation:
Institute for Computational Cosmology, Department of Physics, Durham University, Durham DH1 3LE, UK email: [email protected]
Helen Russell
Affiliation:
Institute of Astronomy, Madingley Rd., Cambridge, CB3 0HA, UK email: [email protected], [email protected]
Andy Fabian
Affiliation:
Institute of Astronomy, Madingley Rd., Cambridge, CB3 0HA, UK email: [email protected], [email protected]
Stefi Baum
Affiliation:
Center for Imaging Science, Rochester Institute of Technology, Rochester, NY 14623, USA email: [email protected]
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Abstract

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We present first results from an imaging survey with the Spitzer Space Telescope of 62 brightest cluster galaxies with optical line emission located in the cores of X-ray luminous clusters selected from the ROSAT All-Sky Survey. We find that 1/3 of these sources have signs of excess infrared emission; 22 objects of 62 are detected at 70 μm and 19 have 8 to 5.8 μm flux ratios above 0.98. The strength of the excess emission correlates with the luminosity of the optical emission lines. Excluding the four systems dominated by an AGN, the excess mid-infrared emission in the remaining brightest cluster galaxies is likely powered by star formation. We find a correlation between mass deposition rate from a cooling flow model for the X-ray emission and the star formation rate estimated from the infrared luminosity. The star formation rates are 1/10 to 1/100 of the mass deposition rates expected in the absence of heating suggesting that the re-heating of the ICM is generally very effective in reducing the amount of mass cooling from the hot phase.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2008

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