Systematic search for tidal features around nearby galaxies: I. Enhanced
  SDSS imaging of the Local Volume
  In hierarchical models of galaxy formation, stellar tidal streams are
expected around most, if not all, galaxies. Although these features may provide
useful diagnostics of the $\Lambda$CDM model, their observational properties
remain poorly constrained because they are challenging to detect and interpret
and have been studied in detail for only a sparse sampling of galaxy
population. More quantitative, systematic approaches are required. We advocate
statistical analysis of the counts and properties of such features in archival
wide-field imaging surveys for a direct comparison against results from
numerical simulations. Thus, in this paper we aim to study systematically the
frequency of occurrence and other observational properties of tidal features
around nearby galaxies. The sample we construct will act as a foundational
dataset for statistical comparison with cosmological models of galaxy
formation. Our approach is based on a visual classification of diffuse features
around a volume-limited sample of nearby galaxies, using a post-processing of
Sloan Digital Sky Survey imaging optimized for the detection of stellar
structure with low surface brightness. At a limiting surface brightness of $28\
\mathrm{mag~arcsec^{-2}}$, 14% of the galaxies in our sample exhibit evidence
of diffuse features likely to have arisen from minor merging events. Our
technique recovers all previously known streams in our sample and yields a
number of new candidates. Consistent with previous studies, coherent arc-like
features and shells are the most common type of tidal structures found in this
study. We conclude that although some detections are ambiguous and could be
corroborated or refuted with deeper imaging, our technique provides a reliable
foundation for the statistical analysis of diffuse circumgalactic features in
wide-area imaging surveys, and for the identification of targets for follow-up
studies.
