Spherical accretion in giant elliptical galaxies: multi-transonicity, shocks, and implications on AGN feedback

• Published in: arXiv.org 2021-03
• Main Authors: Raychaudhuri, Sananda, Ghosh, Shubhrangshu, Joarder, Partha S
• Format: Article
• Language: English
• Subjects: Active galactic nuclei; Ambient temperature; Context; Cosmological constant; Dark matter; Deposition; Elliptical galaxies; Feedback; Galactic clusters; Galactic mass; Space telescopes; Topology
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2103.15508

Isolated massive elliptical galaxies, or that are present at the center of cool-core clusters, are believed to be powered by hot gas accretion directly from their surrounding hot X-ray emitting gaseous medium. This leads to a giant Bondi-type spherical/quasi-spherical accretion flow onto their host SMBHs, with the accretion flow region extending well beyond the Bondi radius. In this work, we present a detailed study of Bondi-type spherical flow in the context of these massive ellipticals by incorporating the effect of entire gravitational potential of the host galaxy in the presence of cosmological constant \(\Lambda\), considering a five-component galactic system (SMBH + stellar + dark matter + hot gas + \(\Lambda\)). The current work is an extension of Ghosh \& Banik (2015), who studied only the cosmological aspect of the problem. The galactic contribution to the potential renders the (adiabatic) spherical flow to become {\it multi-transonic} in nature, with the flow topology and flow structure significantly deviating from that of classical Bondi solution. More notably, corresponding to moderate to higher values of galactic mass-to-light ratios, we obtain Rankine-Hugoniot shocks in spherical wind flows. Galactic potential enhances the Bondi accretion rate. Our study reveals that there is a strict lower limit of ambient temperature below which no Bondi accretion can be triggered; which is as high as \(\sim 9 \times 10^6 \, K\) for flows from hot ISM-phase, indicating that the hot phase tightly regulates the fueling of host nucleus. Our findings may have wider implications, particularly in the context of outflow/jet dynamics, and radio-AGN feedback, associated with these massive galaxies in the contemporary Universe.