The Origin of Faint Tidal Features Around Galaxies in the RESOLVE Survey

TL;DR

This study investigates the frequency and nature of faint tidal features around galaxies in the RESOLVE survey, revealing differences based on gas content and galaxy environment, and suggesting multiple formation mechanisms.

Contribution

It provides the first large-scale analysis of faint tidal features in a local galaxy survey, linking their presence to galaxy properties and environment, and proposing different origins for gas-rich and gas-poor galaxies.

Findings

17% of galaxies show tidal features, with lower frequency in gas-poor galaxies.

Tidal features in gas-poor galaxies are linked to dry mergers or satellite disruption.

Tidal features in gas-rich galaxies are associated with resonant interactions and gas accretion.

Abstract

We study tidal features (TFs) around galaxies in the REsolved Spectroscopy of a Local VolumE (RESOLVE) survey. Our sample consists of 1048 RESOLVE galaxies that overlap with the DECam Legacy Survey, which reaches an r-band 3$\sigma$ depth of $\sim$27.9 mag arcsec$^{-2}$ for a 100 arcsec$^{2}$ feature. Images were masked, smoothed, and inspected for TFs like streams, shells, or tails/arms. We find TFs in 17$^{\pm 2} \%$ of our galaxies, setting a lower limit on the true frequency. The frequency of TFs in the gas-poor (gas-to-stellar mass ratio $<$ 0.1) subsample is lower than in the gas-rich subsample (13$^{\pm 3} \%$ vs. 19$^{\pm 2} \%$). Within the gas-poor subsample, galaxies with TFs have higher stellar and halo masses, $\sim 3\times$ closer distances to nearest neighbors (in the same group), and possibly fewer group members at fixed halo mass than galaxies without TFs, but similar specific star formation rates. These results suggest TFs in gas-poor galaxies are typically streams/shells from dry mergers or satellite disruption. In contrast, the presence of TFs around gas-rich galaxies does not correlate with stellar or halo mass, suggesting these TFs are often tails/arms from resonant interactions. Similar to TFs in gas-poor galaxies, TFs in gas-rich galaxies imply 1.7x closer nearest neighbors in the same group; however, TFs in gas-rich galaxies are associated with diskier morphologies, higher star formation rates, and higher gas content. In addition to interactions with known neighbors, we suggest that TFs in gas-rich galaxies may arise from accretion of cosmic gas and/or gas-rich satellites below the survey limit.