AGN-stimulated Cooling of Hot Gas in Elliptical Galaxies

Abstract

We study the impact of relatively weak AGN feedback on the interstellar medium of intermediate and massive elliptical galaxies. We find that the AGN activity, while globally heating the ISM, naturally stimulates some degree of hot gas cooling on scales of several kpc. This process generates the persistent presence of a cold ISM phase, with mass ranging between 10${}^4$ and $\gtrsim$ 5 $\times$ 10${}^7$ M${}_{\odot }$, where the latter value is appropriate for group centered, massive galaxies. Widespread cooling occurs where the ratio of cooling to free-fall time before the activation of the AGN feedback satisfies $t_{cool}/t_{ff}\lesssim 70$, that is we find a less restrictive threshold than commonly quoted in the literature. This process helps explaining the body of observations of cold gas (both ionized and neutral/molecular) in Ellipticals and, perhaps, the residual star formation detected in many early-type galaxies. The amount and distribution of the off-center cold gas vary irregularly with time. The cold ISM velocity field is irregular, initially sharing the (outflowing) turbulent hot gas motion. Typical velocity dispersions of the cold gas lie in the range 100-200 km/s. Freshly generated cold gas often forms a cold outflow and can appear kinematically misaligned with respect to the stars. We also follow the dust evolution in the hot and cold gas. We find that the internally generated cold ISM has a very low dust content, with representative values of the dust-to-gas ratio of 10${}^{-4}$- 10${}^{-5}$. Therefore, this cold gas can escape detection in the traditional dust-absorption maps.

We better explained formulas in Section 2, to clarify the implementation of dust physics in the code. 23 pages, 12 figures. Published in MNRAS

References in corpus (14)

• Heating Hot Atmospheres with Active Galactic Nuclei
• Evolution of interstellar dust and stardust in the solar neighbourhood
• An Entropy Threshold for Strong H-alpha and Radio Emission in the Cores of Galaxy Clusters
• The role of minor mergers in the recent star formation history of early-type galaxies
• Jet acceleration of the fast molecular outflows in the Seyfert galaxy IC5063
• Formation of cold filaments in cooling flow clusters
• A Strong Correlation between Circumnuclear Dust and Black Hole Accretion in Early-Type Galaxies
• Effect of turbulent diffusion on iron abundance profiles
• Conduction and the Star-Formation Threshold in Brightest Cluster Galaxies
• HD and H2 formation in low-metallicity dusty gas clouds at high redshift
• Stopping Cooling Flows with Jets
• Spitzer Observations of Transient, Extended Dust in Two Elliptical Galaxies: New Evidence of Recent Feedback Energy Release in Galactic Cores
• Creation of the X-ray Cavity Jet and its Radio Lobe in M87/Virgo with Cosmic Rays; Relevance to Relic Radio Sources
• The cold mode: A phenomenological model for the evolution of density perturbations in the intracluster medium

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• Impact of AGN feedback on galaxies and their multiphase ISM across cosmic time
• A Study of High-redshift AGN Feedback in SZ Cluster Samples
• Buoyant AGN bubbles in the quasi-isothermal potential of NGC 1399
• Probing multiphase gas in local massive elliptical galaxies via multiwavelength observations
• Optical Properties of Peaked Spectrum Radio Sources
• Dust Grain Growth at High Redshift: Starburst-driven CMB-Dark Supershells