Merging Cold Fronts in the Galaxy Pair NGC 7619 and NGC 7626
S. W. Randall, C. Jones, R. Kraft, W. R. Forman, and E. O'Sullivan

TL;DR
This study uses Chandra X-ray observations to analyze merger cold fronts in the galaxy pair NGC 7619 and NGC 7626, revealing a major subgroup merger in the Pegasus cluster with implications for galaxy dynamics and intracluster medium interactions.
Contribution
First detailed analysis of merger cold fronts in NGC 7619 and NGC 7626, demonstrating a major subgroup merger in the Pegasus cluster and linking radio jet features to the merger dynamics.
Findings
Galaxies are falling towards each other in the plane of the sky.
Relative velocity of the galaxies is approximately 1190 km/s.
Temperature maps show cool gas entrainment and extension near radio lobes.
Abstract
We present results from {\it Chandra} observations of the galaxy pair NGC 7619 and NGC 7626, the two dominant members of the Pegasus group. The X-ray images show a brightness edge associated with each galaxy, which we identify as merger cold fronts. The edges are sharp, and the axes of symmetry of the edges are roughly anti-parallel, suggesting that these galaxies are falling towards one another in the plane of the sky. The detection of merger cold fronts implies a merging subgroup scenario, since the alternative is that the galaxies are falling into a pre-existing keV halo without a dominant galaxy of its own, and such objects are not observed. We estimate the 3D velocities from the cold fronts and show that the velocity vectors are indeed most likely close to the plane of the sky, with a relative velocity of . The relative velocity is consistent with what is…
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