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Testing the Limits of AGN Feedback and the Onset of Thermal Instability in the Most Rapidly Star-forming Brightest Cluster Galaxies

Calzadilla, Michael S.; McDonald, Michael; Donahue, Megan; McNamara, Brian R.; Fogarty, Kevin; Gaspari, Massimo; Gitti, Myriam; Russell, Helen R.; Tremblay, Grant R.; Voit, G. Mark; Ubertosi, Francesco

Testing the Limits of AGN Feedback and the Onset of Thermal Instability in the Most Rapidly Star-forming Brightest Cluster Galaxies Thumbnail


Michael S. Calzadilla

Michael McDonald

Megan Donahue

Brian R. McNamara

Kevin Fogarty

Massimo Gaspari

Myriam Gitti

Grant R. Tremblay

G. Mark Voit

Francesco Ubertosi


We present new, deep, narrow- and broadband Hubble Space Telescope observations of seven of the most star-forming brightest cluster galaxies (BCGs). Continuum-subtracted [OII] maps reveal the detailed, complex structure of warm (T ∼ 104 K) ionized gas filaments in these BCGs, allowing us to measure spatially resolved star formation rates (SFRs) of ∼60-600 M ⊙yr−1. We compare the SFRs in these systems and others from the literature to their intracluster medium cooling rates ( M ̇ cool ), measured from archival Chandra X-ray data, finding a best-fit relation of log ( SFR ) = ( 1.66 ± 0.17 ) log ( M ̇ cool ) + (−3.22 ± 0.38) with an intrinsic scatter of 0.39 ± 0.09 dex. This steeper-than-unity slope implies an increasingly efficient conversion of hot (T ∼ 107 K) gas into young stars with increasing M ̇ cool , or conversely a gradual decrease in the effectiveness of AGN feedback in the strongest cool cores. We also seek to understand the physical extent of these multiphase filaments that we observe in cluster cores. We show, for the first time, that the average extent of the multiphase gas is always smaller than the radii at which the cooling time reaches 1 Gyr, the t cool/t ff profile flattens, and that X-ray cavities are observed. This implies a close connection between the multiphase filaments, the thermodynamics of the cooling core, and the dynamics of X-ray bubbles. Interestingly, we find a one-to-one correlation between the average extent of cool multiphase filaments and the radius at which the cooling time reaches 0.5 Gyr, which may be indicative of a universal condensation timescale in cluster cores.

Journal Article Type Article
Acceptance Date Oct 3, 2022
Online Publication Date Nov 29, 2022
Publication Date Dec 1, 2022
Deposit Date Dec 5, 2022
Publicly Available Date Dec 15, 2022
Journal Astrophysical Journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 940
Issue 2
Article Number 140
Keywords Space and Planetary Science, Astronomy and Astrophysics
Public URL
Publisher URL


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