An Entropy Threshold for Strong Hα and Radio Emission in the Cores of Galaxy Clusters

Our Chandra X-Ray Observatory archival study of intracluster entropy in a sample of 222 galaxy clusters shows that H? and radio emission from the brightest cluster galaxy are much more pronounced when the cluster's core gas entropy is 30 keV cm2. The prevalence of H? emission below this threshold indicates that it marks a dichotomy between clusters that can harbor multiphase gas and star formation in their cores and those that cannot. The fact that strong central radio emission also appears below this boundary suggests that AGN feedback turns on when the intracluster medium starts to condense, strengthening the case for AGN feedback as the mechanism that limits star formation in the universe's most luminous galaxies.

[1]  M. Donahue,et al.  An Infrared Survey of Brightest Cluster Galaxies. II. Why are Some Brightest Cluster Galaxies Forming Stars? , 2007, Proceedings of the International Astronomical Union.

[2]  D. A. Rafferty,et al.  Conduction and the Star Formation Threshold in Brightest Cluster Galaxies , 2008, 0806.0384.

[3]  M. Donahue,et al.  X-Ray and Optical Filaments in M87 , 2004, astro-ph/0402204.

[4]  R. Kennicutt.  The Rate of star formation in normal disk galaxies , 1983 .

[5]  C. Lawrence,et al.  Optical Spectra of a Complete Sample of Radio Sources. I. The Spectra , 1996 .

[6]  M. Donahue,et al.  Entropy Profiles in the Cores of Cooling Flow Clusters of Galaxies , 2005, astro-ph/0511401.

[7]  G. Kauffmann,et al.  The many lives of active galactic nuclei: cooling flows, black holes and the luminosities and colour , 2005, astro-ph/0508046.

[8]  G. Kriss,et al.  The X-ray emitting gas in poor clusters with central dominant galaxies , 1983 .

[9]  N. Soker,et al.  On the Nature of Feedback Heating in Cooling Flow Clusters , 2004, astro-ph/0407042.

[10]  Oxford,et al.  Breaking the hierarchy of galaxy formation , 2005, astro-ph/0511338.

[11]  M. Ruszkowski,et al.  A Global Stability Analysis of Clusters of Galaxies with Conduction and AGN Feedback Heating , 2008, 0804.3823.

[12]  Volker Springel,et al.  The Many lives of AGN: Cooling flows, black holes and the luminosities and colours of galaxies , 2006, astro-ph/0602065.

[13]  Properties of the galaxy population in hydrodynamical simulations of clusters , 2006, astro-ph/0609191.

[14]  D. A. Rafferty,et al.  A Systematic Study of Radio-induced X-Ray Cavities in Clusters, Groups, and Galaxies , 2004 .

[15]  J. Curran,et al.  SUMSS: a wide-field radio imaging survey of the southern sky – II. The source catalogue , 2003, astro-ph/0303188.

[16]  An investigation of cooling flows and general cluster properties from an X-ray image deprojection analysis of 207 clusters of galaxies , 1997, astro-ph/9707269.

[17]  M. Donahue,et al.  Two Clusters of Galaxies with Radio-quiet Cooling Cores , 2005, astro-ph/0508587.

[18]  M. I. Large,et al.  SUMSS: A Wide-Field Radio Imaging Survey of the Southern Sky. I. Science Goals, Survey Design, and Instrumentation , 1999 .

[19]  H(alpha) Imaging of the Hickson Compact Group 62 , 1996, astro-ph/9607138.

[20]  M. Donahue,et al.  Distant cooling flows , 1992 .

[21]  G. Bryan,et al.  Modified Entropy Models for the Intracluster Medium , 2002, astro-ph/0205240.

[22]  T. Ensslin,et al.  Cosmic ray confinement in fossil cluster bubbles , 2007, 0705.3235.

[23]  G. Voit.  Tracing cosmic evolution with clusters of galaxies , 2004, astro-ph/0410173.

[24]  Jack O. Burns,et al.  The radio properties of cD galaxies in Abell clusters. I - An X-ray selected sample , 1990 .

[25]  M. J. Hardcastle,et al.  Hot and cold gas accretion and feedback in radio-loud active galaxies , 2007 .

[26]  Patrick J. McCarthy,et al.  Dynamical, physical, and chemical properties of emission-line nebulae in cooling flows , 1989 .

[27]  X-ray Spectroscopy of Cooling Clusters , 2005, astro-ph/0512549.

[28]  C. Crawford,et al.  The extended Hα‐emitting filaments surrounding NGC 4696, the central galaxy of the Centaurus cluster , 2005, astro-ph/0507627.

[29]  J. Burns,et al.  Radio emission in the directions of cD and related galaxies in poor clusters. III - VLA observations at 20 cm , 1980 .

[30]  B. McNamara,et al.  Star formation in cooling flows in clusters of galaxies , 1989 .

[31]  L. Cowie,et al.  Long-slit spectroscopy of gas in the cores of X-ray luminous clusters , 1985 .

[32]  P. Nulsen,et al.  Heating Hot Atmospheres with Active Galactic Nuclei , 2007, 0709.2152.

[33]  The ROSAT Brightest Cluster Sample — III. Optical spectra of the central cluster galaxies , 1999, astro-ph/9903057.

[34]  M. Donahue,et al.  Bandpass Dependence of X-Ray Temperatures in Galaxy Clusters , 2008, 0803.3858.

[35]  A. Fabian,et al.  The optical spectra of central galaxies in southern clusters: evidence for star formation , 1987 .

[36]  E. Greisen,et al.  The NRAO VLA Sky Survey , 1996 .

[37]  Richard L. White,et al.  The FIRST Survey: Faint Images of the Radio Sky at twenty centimeters , 1995 .

[38]  G. Ferland,et al.  The origin of molecular hydrogen emission in cooling‐flow filaments★ , 2008, 0802.2535.

[39]  M. Donahue,et al.  A Deep Look at the Emission-Line Nebula in Abell 2597 , 1997, astro-ph/9706107.