Multiphase AGN winds from X-ray irradiated disk atmospheres. (arXiv:2101.09273v3 [astro-ph.GA] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Waters_T/0/1/0/all/0/1">Tim Waters</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Proga_D/0/1/0/all/0/1">Daniel Proga</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dannen_R/0/1/0/all/0/1">Randall Dannen</a>
The mechanism of thermal driving for launching mass outflows is
interconnected with classical thermal instability (TI). In a recent paper, we
demonstrated that as a result of this interconnectedness, radial wind solutions
of X-ray heated flows are prone to becoming clumpy. In this paper, we first
show that the Bernoulli function determines whether or not the entropy mode can
grow due to TI in dynamical flows. Based on this finding, we identify a
critical `unbound’ radius beyond which TI should accompany thermal driving. Our
numerical disk wind simulations support this result and reveal that clumpiness
is a consequence of buoyancy disrupting the stratified structure of steady
state solutions. Namely, instead of a smooth transition layer separating the
highly ionized disk wind from the cold phase atmosphere below, hot bubbles
formed from TI rise up and fragment the atmosphere. These bubbles first appear
within large scale vortices that form below the transition layer, and they
result in the episodic production of distinctive cold phase structures referred
to as irradiated atmospheric fragments (IAFs). Upon interacting with the wind,
IAFs advect outward and develop extended crests. The subsequent disintegration
of the IAFs takes place within a turbulent wake that reaches high elevations
above the disk. We show that this dynamics has the following observational
implications: dips in the absorption measure distribution are no longer
expected within TI zones and there can be a less sudden desaturation of X-ray
absorption lines such as OVIII as well as multiple absorption troughs in
FeXXVK.
The mechanism of thermal driving for launching mass outflows is
interconnected with classical thermal instability (TI). In a recent paper, we
demonstrated that as a result of this interconnectedness, radial wind solutions
of X-ray heated flows are prone to becoming clumpy. In this paper, we first
show that the Bernoulli function determines whether or not the entropy mode can
grow due to TI in dynamical flows. Based on this finding, we identify a
critical `unbound’ radius beyond which TI should accompany thermal driving. Our
numerical disk wind simulations support this result and reveal that clumpiness
is a consequence of buoyancy disrupting the stratified structure of steady
state solutions. Namely, instead of a smooth transition layer separating the
highly ionized disk wind from the cold phase atmosphere below, hot bubbles
formed from TI rise up and fragment the atmosphere. These bubbles first appear
within large scale vortices that form below the transition layer, and they
result in the episodic production of distinctive cold phase structures referred
to as irradiated atmospheric fragments (IAFs). Upon interacting with the wind,
IAFs advect outward and develop extended crests. The subsequent disintegration
of the IAFs takes place within a turbulent wake that reaches high elevations
above the disk. We show that this dynamics has the following observational
implications: dips in the absorption measure distribution are no longer
expected within TI zones and there can be a less sudden desaturation of X-ray
absorption lines such as OVIII as well as multiple absorption troughs in
FeXXVK.
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