Diffuse X-Ray-emitting Gas in Major Mergers

Abstract

Using archived data from the Chandra X-ray telescope, we have extracted the diffuse Xray emission from 49 equal-mass interacting/merging galaxy pairs in a merger sequence, from widely separated pairs to merger remnants. After removal of contributions from unresolved point sources, we compared the diffuse thermal X-ray luminosity from hot gas (L X (gas)) with the global star formation rate (SFR). After correction for absorption within the target galaxy, we do not see strong trend of L X (gas)/SFR with SFR or merger stage for galaxies with SFR > 1 M ⊙ yr −1 . For these galaxies, the median L X (gas)/SFR is 5.5 × 10 39 ((erg s −1 )/M ⊙ yr −1 )), similar to that of normal spiral galaxies. These results suggest that stellar feedback in star forming galaxies reaches an approximately steady state condition, in which a relatively constant fraction of about 2% of the total energy output from supernovae and stellar winds is converted into X-ray flux. Three late-stage merger remnants with low SFRs and high K band luminosities (L K ) have enhanced L X (gas)/SFR; their UV/IR/optical colors suggest that they are post-starburst galaxies, perhaps in the process of becoming ellipticals. Systems with L K < 10 10 L ⊙ have lower L X (gas)/SFR ratios than the other galaxies in our sample, perhaps due to lower gravitational fields or lower metallicities. We see no relation between L X (gas)/SFR and Seyfert activity in this sample, suggesting that feedback from active galactic nuclei is not a major contributor to the hot gas in our sample galaxies.

VEGAS: A VST Early-type Galaxy Survey. III. Mapping the Galaxy Structure, Interactions, and Intragroup Light in the NGC 5018 Group

“…Recently, Chandra X-ray data have been analyzed by Smith et al (2018) to study the diffuse X-ray emitting gas in major mergers. They did a rough classification of the systems in their sample into seven merger stages.…”

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

“…Freely-flowing hot gas produces little X-ray emission, in contrast to hot gas confined by surrounding cooler gas (Hopkins et al 2012a). Observational studies show that for star-forming galaxies, the X-ray luminosity from hot gas, L X (gas), is proportional to the SFR (Strickland et al 2004b;Grimes et al 2005;Mineo et al 2012b;Smith et al 2018). This is in contrast to some theoretical estimates, which predict that L X (gas) should be proportional to SFR 2 (Chevalier & Clegg 1985;Zhang et al 2014).…”

An optical transmission spectrum of the giant planet WASP-36 b

“…The Calar Alto light curve is plotted in Fig. 1 together with the best one reported in the discovery paper (Smith et al 2012) for comparison. The GROND light curves are plotted according to date in Fig.…”

“…In the present work, we study the transiting planetary system WASP-36 (Smith et al 2012). This contains a relatively dense hot Jupiter, WASP-36 b, with mass Mp ≈ 2.3 MJup and radius Rp ≈ 1.3 RJup.…”

“…Figure 1. Transit light curve from Calar Alto (upper; this work) and the best one from the discovery paper (lower; Smith et al 2012). The dates and filters used are indicated.…”