A Chandra X-Ray Investigation of the Violent Interstellar Medium: From Dwarf Starbursts to Ultraluminous Infrared Galaxies
J. Grimes, T. Heckman, D. Strickland
Mar 31, 2005
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The Astrophysical Journal
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Key Takeaway Key Takeaway: The same physical mechanism produces diffuse X-ray emission in dwarf, edge-on, and ultraluminous infrared galaxies, suggesting a galactic "superwind" drives this emission.
Abstract
We have analyzed observations with the Chandra X-Ray Observatory of the diffuse emission by hot gas in seven dwarf starburst galaxies, six edge-on starburst galaxies, and nine ultraluminous infrared galaxies. These systems cover ranges of ~104 in X-ray luminosity, and several thousand in star formation rate and K-band luminosity (a proxy for stellar mass). Despite this range in fundamental parameters, we find that the properties of the diffuse X-ray emission are very similar in all three classes of starburst galaxies. The spectrum of the diffuse emission is well fitted by thermal emission from gas with kT ~ 0.25-0.8 keV and with several times solar abundance ratios of α-elements to Fe. The ratio of the thermal X-ray to far-infrared luminosity is roughly constant, as is the characteristic surface brightness of the diffuse X-ray emission. The size of the diffuse X-ray source increases systematically with both far-infrared and K-band luminosity. All three classes show strong morphological relationships between the regions of hot gas probed by the diffuse X-ray emission and the warm gas probed by optical line emission. These findings suggest that the same physical mechanism is producing the diffuse X-ray emission in the three types of starbursts. These results are consistent with that mechanism being shocks driven by a galactic "superwind," which is powered by the kinetic energy collectively supplied by stellar winds and supernovae in the starburst.