The Hot Gas Exhaust of Starburst Engines in Mergers: Testing Models of Stellar Feedback and Star Formation Regulation

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Using archival data from the Chandra X-ray telescope, we have measured the spatial extent of the hot interstellar gas in a sample of 49 nearby interacting galaxy pairs, mergers, and merger remnants. For systems with SFR > 1 M yr-1, the volume and mass of hot gas are strongly and linearly correlated with the star formation rate (SFR). This supports the idea that stellar/supernovae feedback dominates the production of hot gas in these galaxies. We compared the mass of X-ray-emitting hot gas M X(gas) with the molecular and atomic hydrogen interstellar gas masses in these galaxies (MH2 and MH i, respectively), using published carbon monoxide and 21 cm H i measurements. Systems with higher SFRs have larger M X(gas)/(MH2 + M H i) ratios on average, in agreement with recent numerical simulations of star formation and feedback in merging galaxies. The M X(gas)/( MH2 + M H i) ratio also increases with dust temperature on average. The ratio M X(gas)/SFR is anticorrelated with the Infrared Astronomical Satellite 60-100 μm flux ratio and with the Spitzer 3.6-24 μm color. These trends may be due to variations in the spatial density of young stars, the stellar age, the ratio of young to old stars, the initial mass function, and/or the efficiency of stellar feedback. Galaxies with low SFR (<1 M ⊙ yr-1) and high K band luminosities may have an excess of hot gas relative to the relation for higher SFR galaxies, while galaxies with low K band luminosities (and therefore low stellar masses) may have a deficiency in hot gas, but our sample is not large enough for strong statistical significance.