Gravitational torques dominate the dynamics of accreted gas at $z>2$. (arXiv:2110.05384v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Cadiou_C/0/1/0/all/0/1">Corentin Cadiou</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dubois_Y/0/1/0/all/0/1">Yohan Dubois</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pichon_C/0/1/0/all/0/1">Christophe Pichon</a>
Galaxies form from the accretion of cosmological infall of gas. In the high
redshift Universe, most of this gas infall is expected to be dominated by cold
filamentary flows which connect deep down to the inside of halos, and, hence,
to the vicinity of galaxies. Such cold flows are important since they dominate
the mass and angular momentum acquisition that can make up
rotationally-supported disks at high-redshifts. In hydrodynamical cosmological
simulations of high-resolution zoomed-in halos of a few $10^{11},rm M_odot$
halos at $z=2$ including the physics of star formation and feedback from
supernovae and supermassive black holes, we have studied the angular momentum
acquisition of gas into galaxies, and in particular, the torques acting on the
accretion flows. Torques can be separated into those of gravitational origin,
and hydrodynamical ones driven by pressure gradients. We find that coherent
gravitational torques dominate over pressure torques in the cold phase, and are
hence responsible for the spin-down and realignment of this gas. Pressure
torques display small-scale fluctuations of significant amplitude, but with
very little coherence on the relevant galaxy or halo-scale that would otherwise
allow them to effectively re-orientate the gas flows. Dark matter torques
dominate gravitational torques outside the galaxy, while within the galaxy, the
baryonic component dominates. The circum-galactic medium emerges as the
transition region for angular momentum re-orientation of the cold component
towards the central galaxy’s mid-plane.
Galaxies form from the accretion of cosmological infall of gas. In the high
redshift Universe, most of this gas infall is expected to be dominated by cold
filamentary flows which connect deep down to the inside of halos, and, hence,
to the vicinity of galaxies. Such cold flows are important since they dominate
the mass and angular momentum acquisition that can make up
rotationally-supported disks at high-redshifts. In hydrodynamical cosmological
simulations of high-resolution zoomed-in halos of a few $10^{11},rm M_odot$
halos at $z=2$ including the physics of star formation and feedback from
supernovae and supermassive black holes, we have studied the angular momentum
acquisition of gas into galaxies, and in particular, the torques acting on the
accretion flows. Torques can be separated into those of gravitational origin,
and hydrodynamical ones driven by pressure gradients. We find that coherent
gravitational torques dominate over pressure torques in the cold phase, and are
hence responsible for the spin-down and realignment of this gas. Pressure
torques display small-scale fluctuations of significant amplitude, but with
very little coherence on the relevant galaxy or halo-scale that would otherwise
allow them to effectively re-orientate the gas flows. Dark matter torques
dominate gravitational torques outside the galaxy, while within the galaxy, the
baryonic component dominates. The circum-galactic medium emerges as the
transition region for angular momentum re-orientation of the cold component
towards the central galaxy’s mid-plane.
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