Late-stage galaxy mergers in COSMOS to z~1
C. N. Lackner, J. D. Silverman, M. Salvato, P. Kampczyk, J. S., Kartaltepe, D. Sanders, P. Capak, F. Civano, O. Ilbert, K. Jahnke, A. M., Koekemoer, N. Lee, O. Le Fevre, C. T. Liu, N. Scoville, K. Sheth, S. Toft

TL;DR
This study develops an automated method to identify late-stage galaxy mergers in the COSMOS survey, revealing their increasing rate with redshift and their role in star formation and black hole activity.
Contribution
The paper introduces a new automated technique for detecting late-stage galaxy mergers using median-filtered high-resolution images, improving upon previous pair-finding and morphological methods.
Findings
Approximately 5% of galaxies are late-stage mergers at z~1.
The merger rate increases as (1+z)^{3.8±0.9} with redshift.
Star-forming galaxy merger rate rises steeply with redshift, while quiescent galaxy merger rate shows no significant evolution.
Abstract
The role of major mergers in galaxy and black hole formation is not well constrained. To help address this, we develop an automated method to identify late-stage galaxy mergers before coalescence of the galactic cores. The resulting sample of mergers is distinct from those obtained using pair-finding and morphological indicators. Our method relies on median-filtering of high-resolution images in order to distinguish two concentrated galaxy nuclei at small separations. Using mock images, we derive statistical contamination and incompleteness corrections for the fraction of late-stage mergers. We apply our new method to a magnitude-limited (I < 23) sample of 44,164 galaxies from the COSMOS HST/ACS catalog. Using a mass-complete sample with and , we find ~5% of systems are late-stage mergers with separations between 2.2 and 8 kpc. Correcting…
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