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Title: STARBURST-DRIVEN GALACTIC WINDS: FILAMENT FORMATION AND EMISSION PROCESSES

Abstract

We have performed a series of three-dimensional simulations of the interaction of a supersonic wind with a nonspherical radiative cloud. These simulations are motivated by our recent three-dimensional model of a starburst-driven galactic wind interacting with an inhomogeneous disk, which shows that an optically emitting filament can be formed by the breakup and acceleration of a cloud into a supersonic wind. In this study, we consider the evolution of a cloud with two different geometries (fractal and spherical) and investigate the importance of radiative cooling on the cloud's survival. We have also undertaken a comprehensive resolution study in order to ascertain the effect of the assumed numerical resolution on the results. We find that the ability of the cloud to radiate heat is crucial for its survival, with a radiative cloud experiencing a lower degree of acceleration and having a higher relative Mach number to the flow than in the adiabatic case. This diminishes the destructive effect of the Kelvin-Helmholtz instability on the cloud. While an adiabatic cloud is destroyed over a short period of time, a radiative cloud is broken up via the Kelvin-Helmholtz instability into numerous small, dense cloudlets, which are drawn into the flow to form amore » filamentary structure. The degree of fragmentation is highly dependent on the resolution of the simulation, with the number of cloudlets formed increasing as the Kelvin-Helmholtz instability is better resolved. Nevertheless, there is a clear qualitative trend, with the filamentary structure still persistent at high resolution. The geometry of the cloud affects the speed at which the cloud fragments; a wind more rapidly breaks up the cloud in regions of least density. A cloud with a more inhomogeneous density distribution fragments faster than a cloud with a more uniform structure (e.g., a sphere). We confirm the mechanism behind the formation of the Halpha emitting filaments found in our global simulations of a starburst-driven wind. Based on our resolution study, we conclude that bow shocks around accelerated gas clouds, and their interaction, are the main source of the soft X-ray emission observed in these galactic-scale winds.« less

Authors:
; ;  [1];  [2]
  1. Research School of Astronomy and Astrophysics, Australian National University, Canberra ACT 0200 (Australia)
  2. Institute of Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia)
Publication Date:
OSTI Identifier:
21372000
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 703; Journal Issue: 1; Other Information: DOI: 10.1088/0004-637X/703/1/330; Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCELERATION; EMISSION; FRACTALS; GALAXIES; HELMHOLTZ INSTABILITY; HYDRODYNAMICS; MACH NUMBER; RADIATIVE COOLING; RESOLUTION; SHOCK WAVES; SIMULATION; SOFT X RADIATION; SPHERICAL CONFIGURATION; THREE-DIMENSIONAL CALCULATIONS; CONFIGURATION; COOLING; DIMENSIONLESS NUMBERS; ELECTROMAGNETIC RADIATION; FLUID MECHANICS; INSTABILITY; IONIZING RADIATIONS; MECHANICS; PLASMA INSTABILITY; PLASMA MACROINSTABILITIES; RADIATIONS; VELOCITY; X RADIATION

Citation Formats

Cooper, Jackie L, Bicknell, Geoffrey V, Sutherland, Ralph S, and Bland-Hawthorn, Joss. STARBURST-DRIVEN GALACTIC WINDS: FILAMENT FORMATION AND EMISSION PROCESSES. United States: N. p., 2009. Web. doi:10.1088/0004-637X/703/1/330.
Cooper, Jackie L, Bicknell, Geoffrey V, Sutherland, Ralph S, & Bland-Hawthorn, Joss. STARBURST-DRIVEN GALACTIC WINDS: FILAMENT FORMATION AND EMISSION PROCESSES. United States. https://doi.org/10.1088/0004-637X/703/1/330
Cooper, Jackie L, Bicknell, Geoffrey V, Sutherland, Ralph S, and Bland-Hawthorn, Joss. 2009. "STARBURST-DRIVEN GALACTIC WINDS: FILAMENT FORMATION AND EMISSION PROCESSES". United States. https://doi.org/10.1088/0004-637X/703/1/330.
@article{osti_21372000,
title = {STARBURST-DRIVEN GALACTIC WINDS: FILAMENT FORMATION AND EMISSION PROCESSES},
author = {Cooper, Jackie L and Bicknell, Geoffrey V and Sutherland, Ralph S and Bland-Hawthorn, Joss},
abstractNote = {We have performed a series of three-dimensional simulations of the interaction of a supersonic wind with a nonspherical radiative cloud. These simulations are motivated by our recent three-dimensional model of a starburst-driven galactic wind interacting with an inhomogeneous disk, which shows that an optically emitting filament can be formed by the breakup and acceleration of a cloud into a supersonic wind. In this study, we consider the evolution of a cloud with two different geometries (fractal and spherical) and investigate the importance of radiative cooling on the cloud's survival. We have also undertaken a comprehensive resolution study in order to ascertain the effect of the assumed numerical resolution on the results. We find that the ability of the cloud to radiate heat is crucial for its survival, with a radiative cloud experiencing a lower degree of acceleration and having a higher relative Mach number to the flow than in the adiabatic case. This diminishes the destructive effect of the Kelvin-Helmholtz instability on the cloud. While an adiabatic cloud is destroyed over a short period of time, a radiative cloud is broken up via the Kelvin-Helmholtz instability into numerous small, dense cloudlets, which are drawn into the flow to form a filamentary structure. The degree of fragmentation is highly dependent on the resolution of the simulation, with the number of cloudlets formed increasing as the Kelvin-Helmholtz instability is better resolved. Nevertheless, there is a clear qualitative trend, with the filamentary structure still persistent at high resolution. The geometry of the cloud affects the speed at which the cloud fragments; a wind more rapidly breaks up the cloud in regions of least density. A cloud with a more inhomogeneous density distribution fragments faster than a cloud with a more uniform structure (e.g., a sphere). We confirm the mechanism behind the formation of the Halpha emitting filaments found in our global simulations of a starburst-driven wind. Based on our resolution study, we conclude that bow shocks around accelerated gas clouds, and their interaction, are the main source of the soft X-ray emission observed in these galactic-scale winds.},
doi = {10.1088/0004-637X/703/1/330},
url = {https://www.osti.gov/biblio/21372000}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 703,
place = {United States},
year = {Sun Sep 20 00:00:00 EDT 2009},
month = {Sun Sep 20 00:00:00 EDT 2009}
}