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Simulations of disk galaxies with cosmic ray driven galactic winds

Booth, C. M. ; Agertz, Oscar LU ; Kravtsov, Andrey V. and Gnedin, Nickolay Y. (2013) In Astrophysical Journal Letters 777(1).
Abstract

We present results from high-resolution hydrodynamic simulations of isolated Small Magellanic Cloud (SMC)- and Milky-Way-sized galaxies that include a model for feedback from galactic cosmic rays (CRs). We find that CRs are naturally able to drive winds with mass loading factors of up to ∼10 in dwarf systems. The scaling of the mass loading factor with circular velocity between the two simulated systems is consistent with η ∝ v 1-2
circ required to reproduce the faint end of the galaxy luminosity function. In addition, simulations with CR feedback reproduce both the normalization and the slope of the observed trend of wind velocity with galaxy circular velocity. We find that winds in simulations with CR... (More)

We present results from high-resolution hydrodynamic simulations of isolated Small Magellanic Cloud (SMC)- and Milky-Way-sized galaxies that include a model for feedback from galactic cosmic rays (CRs). We find that CRs are naturally able to drive winds with mass loading factors of up to ∼10 in dwarf systems. The scaling of the mass loading factor with circular velocity between the two simulated systems is consistent with η ∝ v 1-2
circ required to reproduce the faint end of the galaxy luminosity function. In addition, simulations with CR feedback reproduce both the normalization and the slope of the observed trend of wind velocity with galaxy circular velocity. We find that winds in simulations with CR feedback exhibit qualitatively different properties compared to supernova-driven winds, where most of acceleration happens violently in situ near star forming sites. The CR-driven winds are accelerated gently by the large-scale pressure gradient established by CRs diffusing from the star-forming galaxy disk out into the halo. The CR-driven winds also exhibit much cooler temperatures and, in the SMC-sized system, warm (T ∼ 104 K) gas dominates the outflow. The prevalence of warm gas in such outflows may provide a clue as to the origin of ubiquitous warm gas in the gaseous halos of galaxies detected via absorption lines in quasar spectra.

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author
; ; and
publishing date
type
Contribution to journal
publication status
published
keywords
cosmic rays, galaxies: formation, methods: numerical
in
Astrophysical Journal Letters
volume
777
issue
1
article number
L16
publisher
IOP Publishing
external identifiers
  • scopus:84886234920
ISSN
2041-8205
DOI
10.1088/2041-8205/777/1/L16
language
English
LU publication?
no
id
3a38b8f6-24d3-40d4-b362-b75a7af65ba9
date added to LUP
2019-02-07 11:21:14
date last changed
2020-12-29 02:07:55
@article{3a38b8f6-24d3-40d4-b362-b75a7af65ba9,
  abstract     = {<p>We present results from high-resolution hydrodynamic simulations of isolated Small Magellanic Cloud (SMC)- and Milky-Way-sized galaxies that include a model for feedback from galactic cosmic rays (CRs). We find that CRs are naturally able to drive winds with mass loading factors of up to ∼10 in dwarf systems. The scaling of the mass loading factor with circular velocity between the two simulated systems is consistent with η ∝ v <sup>1-2</sup><br>
<sub>circ</sub> required to reproduce the faint end of the galaxy luminosity function. In addition, simulations with CR feedback reproduce both the normalization and the slope of the observed trend of wind velocity with galaxy circular velocity. We find that winds in simulations with CR feedback exhibit qualitatively different properties compared to supernova-driven winds, where most of acceleration happens violently in situ near star forming sites. The CR-driven winds are accelerated gently by the large-scale pressure gradient established by CRs diffusing from the star-forming galaxy disk out into the halo. The CR-driven winds also exhibit much cooler temperatures and, in the SMC-sized system, warm (T ∼ 10<sup>4</sup> K) gas dominates the outflow. The prevalence of warm gas in such outflows may provide a clue as to the origin of ubiquitous warm gas in the gaseous halos of galaxies detected via absorption lines in quasar spectra.</p>},
  author       = {Booth, C. M. and Agertz, Oscar and Kravtsov, Andrey V. and Gnedin, Nickolay Y.},
  issn         = {2041-8205},
  language     = {eng},
  month        = {11},
  number       = {1},
  publisher    = {IOP Publishing},
  series       = {Astrophysical Journal Letters},
  title        = {Simulations of disk galaxies with cosmic ray driven galactic winds},
  url          = {http://dx.doi.org/10.1088/2041-8205/777/1/L16},
  doi          = {10.1088/2041-8205/777/1/L16},
  volume       = {777},
  year         = {2013},
}