An Infrared Survey of Brightest Cluster Galaxies. II. Why are Some Brightest Cluster Galaxies Forming Stars?

O'Dea, C.P.; Baum, S.A.; Privon, G.; Noel-Storr, J.; Quillen, A.C.; Zufelt, N.; Park, J.; Edge, A.; Russell, H.; Fabian, A.C.; Donahue, M.; Sarazin, C.L.; McNamara, B.; Bregman, J.N.; Egami, E.

doi:10.1086/588212

An Infrared Survey of Brightest Cluster Galaxies. II. Why are Some Brightest Cluster Galaxies Forming Stars?

O'Dea, C.P.; Baum, S.A.; Privon, G.; Noel-Storr, J.; Quillen, A.C.; Zufelt, N.; Park, J.; Edge, A.; Russell, H.; Fabian, A.C.; Donahue, M.; Sarazin, C.L.; McNamara, B.; Bregman, J.N.; Egami, E.

Authors

C.P. O'Dea

S.A. Baum

G. Privon

J. Noel-Storr

A.C. Quillen

N. Zufelt

J. Park

Professor Alastair Edge alastair.edge@durham.ac.uk
Professor

H. Russell

A.C. Fabian

M. Donahue

C.L. Sarazin

B. McNamara

J.N. Bregman

E. Egami

Abstract

Quillen et al. presented 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. They found that at least half of these sources have signs of excess IR emission. Here we discuss the nature of the IR emission and its implications for cool core clusters. The strength of the mid-IR excess emission correlates with the luminosity of the optical emission lines. Excluding the four systems dominated by an AGN, the excess mid-IR emission in the remaining brightest cluster galaxies is likely related to star formation. The mass of molecular gas (estimated from CO observations) is correlated with the IR luminosity as found for normal star-forming galaxies. The gas depletion timescale is about 1 Gyr. The physical extent of the IR excess is consistent with that of the optical emission-line nebulae. This supports the hypothesis that star formation occurs in molecular gas associated with the emission-line nebulae and with evidence that the emission-line nebulae are mainly powered by ongoing star formation. We find a correlation between mass deposition rates () estimated from the X-ray emission and the star formation rates estimated from the IR luminosity. The star formation rates are 1/10 to 1/100 of the mass deposition rates, suggesting that the reheating of the intracluster medium is generally very effective in reducing the amount of mass cooling from the hot phase but not eliminating it completely.

Citation

O'Dea, C., Baum, S., Privon, G., Noel-Storr, J., Quillen, A., Zufelt, N., …Egami, E. (2008). An Infrared Survey of Brightest Cluster Galaxies. II. Why are Some Brightest Cluster Galaxies Forming Stars?. Astrophysical Journal, 681(2), 1035-1045. https://doi.org/10.1086/588212

Journal Article Type	Article
Publication Date	Jul 1, 2008
Deposit Date	Jan 30, 2012
Publicly Available Date	Sep 4, 2013
Journal	Astrophysical Journal
Print ISSN	0004-637X
Electronic ISSN	1538-4357
Publisher	American Astronomical Society
Peer Reviewed	Peer Reviewed
Volume	681
Issue	2
Pages	1035-1045
DOI	https://doi.org/10.1086/588212
Keywords	Cooling flow, Galaxies, Clusters, Elliptical and lenticular, cD, Star formation, Infrared.