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

By K. Cavagnolo, M. Donahue, G. Mark Voit, Ming Sun. 2008

193 citations recorded by the source corpus.

Our Chandra X-Ray Observatory archival study of intracluster entropy in a sample of 222 galaxy clusters shows that Hα 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 Hα 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.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/838735f7208b4dfe2c59ffe8b00b187bf3490656

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. P. Hopkins
2. R. Maiolino
3. L. Hernquist
4. D. M. Alexander
5. Sylvain Veilleux
6. P. Best
7. T. Heckman
8. E. Quataert

Citations in the corpus

• Thermal instability and the feedback regulation of hot haloes in clusters, groups and galaxies (2011, background): “1 in Cavagnolo et al. 2008).”
• CAUSE AND EFFECT OF FEEDBACK: MULTIPHASE GAS IN CLUSTER CORES HEATED BY AGN JETS (2011, background): “Cavagnolo et al. (2008), Voit et al. (2008) and McDonald et al. (2011a) have shown the existence of a tight correlation between the amount of cold gas and the ICM entropy or the cooling time.”
• The Coevolution of Galaxies and Supermassive Black Holes: Insights from Surveys of the Contemporary Universe (2014, background): “Observationally, cool clouds and filaments are almost universally observed in galaxies, groups and clusters with cooling times significantly below the Hubble time, but not in systems with higher gas entropy (e.g. Hu et al. 1985, Cavagnolo et al. 2008).”
• AGN wind scaling relations and the co-evolution of black holes and galaxies (2017, background): “Interestingly, only the brightest central galaxies (BCGs) in clusters/groups with low inner entropy (short cooling time) have an active nucleus, and are actively forming stars (Cavagnolo et al. 2008, 2009).”
• ON THE ORIGIN OF THE EXTENDED Hα FILAMENTS IN COOLING FLOW CLUSTERS (2010, background): “However, while previous authors (e.g., Cavagnolo et al. 2008) have found that the central entropy, K0, is much lower in clusters with Hα emission, we find that the entropy is lower everywhere interior to the cooling radius for clusters with extended Hα emission.”
• LoCuSS: the connection between brightest cluster galaxy activity, gas cooling and dynamical disturbance of X‐ray cluster cores (2009, background): “…the BCG and thepeak of the cluster X-ray emission as in important parameter in understanding the activity of the BCG, both in terms of star formation (e.g.Edwards et al. 2007; Bildfell et al. 2008; Cavagnolo et al. 2008) and AGN radio emission (e.g.Cavagnolo et al. 2008; Mittal et al. 2008).”
• Chaotic cold accretion on to black holes (2013, background): “This threshold can also be related to the observed entropy threshold, K ≡ kBT /n2/3e ∼ 30 keV cm2, below which substantial star formation is triggered and extended multiphase gas is observed (Cavagnolo et al. 2008; Rafferty, McNamara & Nulsen 2008).”
• INTRACLUSTER MEDIUM ENTROPY PROFILES FOR A CHANDRA ARCHIVAL SAMPLE OF GALAXY CLUSTERS (2009, methodology): “Later in this paper, and in Cavagnolo et al. (2008a), we focus much of our discussion on the parameter K0 so it is worth clarifying what K0 does not represent.”