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

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-circle dot 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 (M-H2 and M-H 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)/(M-H2 + 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 mu m flux ratio and with the Spitzer 3.6-24 mu m 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-circle dot 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.