Exploring the reality of density substructures in the Palomar 5 stellar
  stream
  We present an analysis of the presence of substructures in the stellar stream
of the Palomar 5 globular cluster, as derived from Sloan Digital Sky Survey
data. Using a matched filter technique, we recover the positions and sizes of
overdensities reported in previous studies. To explore the reality of these
structures, we also create an artificial model of the stream, in which we
construct a realistic background on top of which we add a perfectly smooth
stream structure, taking into account the effects of photometric completeness
and interstellar extinction. We find that the smooth artificial stream then
shows similarly-pronounced substructures as the real structure. Interestingly,
our best-fit N-body simulation does display real projected density variations
linked to stellar epicyclic motions, but these become less significant when
taking into account the SDSS star-count constraints. The substructures found
when applying our matched filter technique to the N-body particles converted
into observable stars are thus mostly unrelated to these epicyclic motions.
This analysis suggests that the majority of the previously-detected
substructures along the tidal tail of Palomar 5 are artefacts of observational
inhomogeneities.
