Ejective and preventative: the IllustrisTNG black hole feedback and its effects on the thermodynamics of the gas within and around galaxies. (arXiv:2004.06132v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Zinger_E/0/1/0/all/0/1">Elad Zinger</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Pillepich_A/0/1/0/all/0/1">Annalisa Pillepich</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Nelson_D/0/1/0/all/0/1">Dylan Nelson</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Weinberger_R/0/1/0/all/0/1">Rainer Weinberger</a> (3), <a href="http://arxiv.org/find/astro-ph/1/au:+Pakmor_R/0/1/0/all/0/1">R&#xfc;diger Pakmor</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Springel_V/0/1/0/all/0/1">Volker Springel</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Hernquist_L/0/1/0/all/0/1">Lars Hernquist</a> (3), <a href="http://arxiv.org/find/astro-ph/1/au:+Marinacci_F/0/1/0/all/0/1">Federico Marinacci</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Vogelsberger_M/0/1/0/all/0/1">Mark Vogelsberger</a> (5) ( (1) Max-Planck-Institut f&#xfc;r Astronomie, (2) Max-Planck-Institut f&#xfc;r Astrophysik, (3) Institute for Theory and Computation, Harvard-Smithsonian Center for Astrophysics, (4) Department of Physics &amp; Astronomy, University of Bologna, (5) Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology)

Supermassive black holes (SMBHs) which reside at the centres of galaxies can
inject vast amounts of energy into the surrounding gas and are thought to be a
viable mechanism to quench star-formation in massive galaxies. Here we study
the $10^{9-12.5},mathrm{M_odot}$ stellar mass central galaxy population of
the IllustrisTNG simulation, specifically the TNG100 and TNG300 volumes at
$z=0$, and show how the three components – SMBH, galaxy, and circumgalactic
medium (CGM) – are interconnected in their evolution. We find that gas entropy
is a sensitive diagnostic of feedback injection. In particular, we demonstrate
how the onset of the low-accretion BH feedback mode, realised in the
IllustrisTNG model as a kinetic, BH-driven wind, leads not only to
star-formation quenching at stellar masses $gtrsim10^{10.5},mathrm{M_odot}$
but also to a change in thermodynamic properties of the (non-star-forming) gas,
both within the galaxy and beyond. The IllustrisTNG kinetic feedback from SMBHs
increases the average gas entropy, within the galaxy and in the CGM,
lengthening typical gas cooling times from $10-100, mathrm{Myr}$ to
$1-10,mathrm{Gyr}$, effectively ceasing ongoing star-formation and inhibiting
radiative cooling and future gas accretion. In practice, the same AGN feedback
channel is simultaneously `ejective’ and `preventative’ and leaves an imprint
on the temperature, density, entropy, and cooling times also in the outer
reaches of the gas halo, up to distances of several hundred kiloparsecs. In the
IllustrisTNG model, a long-lasting quenching state can occur for a
heterogeneous CGM, whereby the hot and dilute CGM gas of quiescent galaxies
contains regions of low-entropy gas with short cooling times.

Supermassive black holes (SMBHs) which reside at the centres of galaxies can
inject vast amounts of energy into the surrounding gas and are thought to be a
viable mechanism to quench star-formation in massive galaxies. Here we study
the $10^{9-12.5},mathrm{M_odot}$ stellar mass central galaxy population of
the IllustrisTNG simulation, specifically the TNG100 and TNG300 volumes at
$z=0$, and show how the three components – SMBH, galaxy, and circumgalactic
medium (CGM) – are interconnected in their evolution. We find that gas entropy
is a sensitive diagnostic of feedback injection. In particular, we demonstrate
how the onset of the low-accretion BH feedback mode, realised in the
IllustrisTNG model as a kinetic, BH-driven wind, leads not only to
star-formation quenching at stellar masses $gtrsim10^{10.5},mathrm{M_odot}$
but also to a change in thermodynamic properties of the (non-star-forming) gas,
both within the galaxy and beyond. The IllustrisTNG kinetic feedback from SMBHs
increases the average gas entropy, within the galaxy and in the CGM,
lengthening typical gas cooling times from $10-100, mathrm{Myr}$ to
$1-10,mathrm{Gyr}$, effectively ceasing ongoing star-formation and inhibiting
radiative cooling and future gas accretion. In practice, the same AGN feedback
channel is simultaneously `ejective’ and `preventative’ and leaves an imprint
on the temperature, density, entropy, and cooling times also in the outer
reaches of the gas halo, up to distances of several hundred kiloparsecs. In the
IllustrisTNG model, a long-lasting quenching state can occur for a
heterogeneous CGM, whereby the hot and dilute CGM gas of quiescent galaxies
contains regions of low-entropy gas with short cooling times.

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