Hot Atmospheres, Cold Gas, AGN Feedback and the Evolution of Early Type Galaxies: a Topical Perspective. (arXiv:1811.05004v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Werner_N/0/1/0/all/0/1">N. Werner</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+McNamara_B/0/1/0/all/0/1">B. R. McNamara</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Churazov_E/0/1/0/all/0/1">E. Churazov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Scannapieco_E/0/1/0/all/0/1">E. Scannapieco</a>

Most galaxies comparable to or larger than the mass of the Milky Way host
hot, X-ray emitting atmospheres, and many such galaxies are radio sources. Hot
atmospheres and radio jets and lobes are the ingredients of radio-mechanical
active galactic nucleus (AGN) feedback. While a consensus has emerged that such
feedback suppresses cooling of hot cluster atmospheres, less attention has been
paid to massive galaxies where similar mechanisms are at play. Observation
indicates that the atmospheres of elliptical and S0 galaxies are largely
primordial, augmented to some degree by stellar mass loss. Their atmospheres
have entropy and cooling time profiles that are remarkably similar to those of
central cluster galaxies. About half display filamentary or disky nebulae of
cool and cold gas, much of which has likely cooled from the hot atmospheres. We
review the observational and theoretical perspectives on thermal instabilities
in galactic atmospheres and the evidence that AGN heating is able to roughly
balance the atmospheric cooling. Such heating and cooling may be regulating
star formation in all massive spheroids at late times.

Most galaxies comparable to or larger than the mass of the Milky Way host
hot, X-ray emitting atmospheres, and many such galaxies are radio sources. Hot
atmospheres and radio jets and lobes are the ingredients of radio-mechanical
active galactic nucleus (AGN) feedback. While a consensus has emerged that such
feedback suppresses cooling of hot cluster atmospheres, less attention has been
paid to massive galaxies where similar mechanisms are at play. Observation
indicates that the atmospheres of elliptical and S0 galaxies are largely
primordial, augmented to some degree by stellar mass loss. Their atmospheres
have entropy and cooling time profiles that are remarkably similar to those of
central cluster galaxies. About half display filamentary or disky nebulae of
cool and cold gas, much of which has likely cooled from the hot atmospheres. We
review the observational and theoretical perspectives on thermal instabilities
in galactic atmospheres and the evidence that AGN heating is able to roughly
balance the atmospheric cooling. Such heating and cooling may be regulating
star formation in all massive spheroids at late times.

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