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