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Probing the gaseous halo of galaxies through non-thermal emission from AGN-driven outflows

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(2015)cite arxiv:1506.05470Comment: 12 pages, 7 figures, 1 table, submitted to MNRAS.

Abstract

Feedback from outflows driven by active galactic nuclei (AGN) can affect the distribution and properties of the gaseous halos of galaxies. We study the hydrodynamics and non-thermal emission from the forward outflow shock produced by an AGN-driven outflow. We consider a few possible profiles for the halo gas density, self-consistently constrained by the halo mass, redshift and the disk baryonic concentration of the galaxy. We show that the outflow velocity levels off at $10^3\,km\, s^-1$ within the scale of the galaxy disk. Typically, the outflow can reach the virial radius around the time when the AGN shuts off. We show that the outflows are energy-driven, consistently with observations. The outflow shock lights up the halos of massive galaxies across a broad wavelength range. For Milky Way (MW) mass halos, radio observations by The Jansky Very Large Array (JVLA) and The Square Kilometer Array (SKA) and infrared/optical observations by The James Webb Space Telescope (JWST) and Hubble Space Telescope (HST) can detect the emission signal of angular size $8"$ from galaxies out to redshift $z\sim5$. Millimeter observations by The Atacama Large Millimeter/submillimeter Array (ALMA) are sensitive to non-thermal emission of angular size $18"$ from galaxies at redshift $złesssim1$, while X-ray observations by Chandra, XMM-Newton and The Advanced Telescope for High Energy Astrophysics (ATHENA) is limited to local galaxies ($z0.1$) with an emission angular size of $\sim2'$. Overall, the extended non-thermal emission provides a new way of probing the gaseous halos of galaxies at high redshifts.

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