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Deep Chandra Observations of M84: AGN Feeding and Feedback from Kiloparsec Scales to the Bondi Radius

Presentation #106.56 in the session “AGN (Poster)”.

Published onApr 01, 2022
Deep Chandra Observations of M84: AGN Feeding and Feedback from Kiloparsec Scales to the Bondi Radius

The interplay between sub-kiloparsec (sub-kpc) scale accretion flows onto active galactic nuclei (AGN) and the outflows they power remains a key uncertainty for understanding both black hole accretion and AGN feedback in early type galaxies. We present the deepest Chandra observation to date of the elliptical galaxy M84 in the Virgo Cluster, totaling over 840 kiloseconds (ks) including both legacy data and that obtained from a recent long (730 ks) campaign. The increased signal to noise provided by such a deep observation allows us to study the structure of the accretion flow feeding the supermassive black hole in the center of M84 from the kpc scales of the X-ray halo to the Bondi radius of the black hole. M84 is one of only four systems in which the Bondi radius can be spatially resolved by Chandra. We produce temperature and metallicity maps of the large-scale H-shaped filaments carved out by the AGN’s radio jets. By modeling the bright nuclear emission from the AGN in the same way as has been done for Virgo’s brightest cluster galaxy, M87, we are able to produce temperature, metallicity, and deprojected density profiles in four sectors about the AGN up to and just within the Bondi radius. We find that rather than being dictated by the gravitational potential of the black hole as would be expected in classical Bondi accretion, the accretion flow in M84 is strongly influenced by the bipolar radio jets emanating from the central AGN. Along the jet axis, the density profile is consistent with ne ~ r-1; however, there is a systematic flattening of the profiles perpendicular to the jet. The radio jets produce a significant asymmetry in the accretion flow, violating a key assumption of the Bondi solution. Temperature in the inner kiloparsec is approximately constant, with only a slight increase from 0.6 to 0.7 keV approaching the Bondi radius, and we find no evidence for a temperature increase imposed by the potential of the black hole. While we are unable to detect a second temperature component in the inner kpc, we find evidence for multi-temperature gas near the Bondi radius in the form of a steep metallicity gradient. The Bondi accretion rate exceeds the inferred accretion rate based on AGN jet power and luminosity by over an order of magnitude, consistent with previous findings in M87. Because M84 is far less luminous than M87 while still hosting a powerful radio jet, our measurements provide unique insight into the large-scale feeding of AGN responsible for radio mode feedback in clusters of galaxies.


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