On the lifetime of merger features of equal-mass disk mergers

TL;DR

This study uses numerical simulations to analyze how long post-merger features of equal-mass galaxy mergers remain visible under different observational conditions, highlighting the importance of survey depth and environment.

Contribution

It provides new insights into the visibility duration of merger features based on simulation data, considering various initial conditions and environments.

Findings

Merger-feature visibility is roughly twice the coalescence time at 25 mag/arcsec^2 surface brightness.

Deeper imaging (28 mag/arcsec^2) doubles the detectable merger-feature time.

Cluster environments significantly reduce the visibility duration of merger features.

Abstract

Detecting post-merger features of merger remnants is highly dependent on the depth of observation images. However, it has been poorly discussed how long the post-merger features are visible under different observational conditions. We investigate a merger-feature time useful for understanding the morphological transformation of galaxy mergers via numerical simulations. We use N-body/hydrodynamic simulations, including gas cooling, star formation, and supernova feedback. We run a set of simulations with various initial orbital configurations and with progenitor galaxies having different morphological properties mainly for equal-mass mergers. As reference models, we ran additional simulations for non-equal mass mergers and mergers in a large halo potential. Mock images using the SDSS $r$ band are synthesized to estimate a merger-feature times and compare it between the merger simulations. The mock images suggest that the post-merger features involve a small fraction of stars, and the merger-feature time depends on galaxy interactions. In an isolated environment, the merger-feature time is, on average, $\sim$ 2 times the final coalescence time for a shallow surface bright limit of 25 mag/arcsec^2. For a deeper surface brightness limit of 28 mag/arcsec^2, however, the merger-feature time is a factor of two longer, which is why the detection of post-merger features using shallow surveys has been difficult. Tidal force of a cluster potential is effective in stripping post-merger features out and reduces the merger-feature time.