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

Abstract

Abstract 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 ( and M H i , respectively), using published carbon monoxide and 21 cm H i measurements. Systems with higher SFRs have larger M X(gas)/( + 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 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.