Galaxy-wide outflows: cold gas and star formation at high speeds
K. Zubovas, and A. King. (2014)cite arxiv:1401.0392Comment: 8 pages, 3 figures. Accepted for publication in MNRAS.
Abstract
Several active galaxies show strong evidence for fast ($v_out \sim
1000~km\,s^-1$) massive ($M =$ several $1000~\msun\,\rm
yr^-1$) gas outflows. Such outflows are expected on theoretical grounds once
the central supermassive black hole reaches the mass set by the $M - \sigma$
relation, and may be what makes galaxies become red and dead. Despite their
high velocities, which imply temperatures far above those necessary for
molecule dissociation, the outflows contain large amounts of molecular gas. To
understand this surprising result, we investigate the gas cooling and show that
the outflows cannot stably persist in high--temperature states. Instead the
outflowing gas forms a two--phase medium, with cold dense molecular clumps
mixed with hot tenuous gas, as observed. We also show that efficient cooling
leads to star formation, providing an observable outflow signature. The central
parts of the outflows can be intrinsically luminous gamma--ray sources,
provided that the central black hole is still strongly accreting. We note also
that these outflows can persist for $10^8$~yr after the central AGN has
turned off, so that many observed outflows (particularly with high speeds)
otherwise assumed to be driven by starbursts might also be of this type.
Description
[1401.0392] Galaxy-wide outflows: cold gas and star formation at high speeds
%0 Generic
%1 zubovas2014galaxywide
%A Zubovas, Kastytis
%A King, Andrew
%D 2014
%K cooling gas molecular outflows
%T Galaxy-wide outflows: cold gas and star formation at high speeds
%U http://arxiv.org/abs/1401.0392
%X Several active galaxies show strong evidence for fast ($v_out \sim
1000~km\,s^-1$) massive ($M =$ several $1000~\msun\,\rm
yr^-1$) gas outflows. Such outflows are expected on theoretical grounds once
the central supermassive black hole reaches the mass set by the $M - \sigma$
relation, and may be what makes galaxies become red and dead. Despite their
high velocities, which imply temperatures far above those necessary for
molecule dissociation, the outflows contain large amounts of molecular gas. To
understand this surprising result, we investigate the gas cooling and show that
the outflows cannot stably persist in high--temperature states. Instead the
outflowing gas forms a two--phase medium, with cold dense molecular clumps
mixed with hot tenuous gas, as observed. We also show that efficient cooling
leads to star formation, providing an observable outflow signature. The central
parts of the outflows can be intrinsically luminous gamma--ray sources,
provided that the central black hole is still strongly accreting. We note also
that these outflows can persist for $10^8$~yr after the central AGN has
turned off, so that many observed outflows (particularly with high speeds)
otherwise assumed to be driven by starbursts might also be of this type.
@misc{zubovas2014galaxywide,
abstract = {Several active galaxies show strong evidence for fast ($v_{\rm out} \sim
1000~{\rm km\,s}^{-1}$) massive ($\dot{M} =$ several $\times 1000~\msun\,{\rm
yr}^{-1}$) gas outflows. Such outflows are expected on theoretical grounds once
the central supermassive black hole reaches the mass set by the $M - \sigma$
relation, and may be what makes galaxies become red and dead. Despite their
high velocities, which imply temperatures far above those necessary for
molecule dissociation, the outflows contain large amounts of molecular gas. To
understand this surprising result, we investigate the gas cooling and show that
the outflows cannot stably persist in high--temperature states. Instead the
outflowing gas forms a two--phase medium, with cold dense molecular clumps
mixed with hot tenuous gas, as observed. We also show that efficient cooling
leads to star formation, providing an observable outflow signature. The central
parts of the outflows can be intrinsically luminous gamma--ray sources,
provided that the central black hole is still strongly accreting. We note also
that these outflows can persist for $\sim 10^8$~yr after the central AGN has
turned off, so that many observed outflows (particularly with high speeds)
otherwise assumed to be driven by starbursts might also be of this type.},
added-at = {2014-01-03T12:50:58.000+0100},
author = {Zubovas, Kastytis and King, Andrew},
biburl = {https://www.bibsonomy.org/bibtex/2e579a69fdac20e51a0d6243a03f89129/miki},
description = {[1401.0392] Galaxy-wide outflows: cold gas and star formation at high speeds},
interhash = {8e8a57fe729ca5e8bf2625ffa46c334a},
intrahash = {e579a69fdac20e51a0d6243a03f89129},
keywords = {cooling gas molecular outflows},
note = {cite arxiv:1401.0392Comment: 8 pages, 3 figures. Accepted for publication in MNRAS},
timestamp = {2014-01-03T12:50:58.000+0100},
title = {Galaxy-wide outflows: cold gas and star formation at high speeds},
url = {http://arxiv.org/abs/1401.0392},
year = 2014
}