Discovery of Extended Tidal Tails around the Globular Cluster Palomar 13
  We use photometry from the DECam Legacy Survey to detect candidate tidal
tails extending ~5 deg on either side of the Palomar 13 globular cluster. The
tails are aligned with the proper motion of Palomar 13 and are consistent with
its old, metal-poor stellar population. We identify three RR Lyrae stars that
are plausibly associated with the tails, in addition to four previously known
in the cluster. From these RR Lyrae stars, we find that the mean distance to
the cluster and tails is $23.6 \pm 0.2$ kpc and estimate the total (initial)
luminosity of the cluster to be $L_V=5.1^{+9.7}_{-3.4}\times 10^3 L_\odot$,
consistent with previous claims that its initial luminosity was higher than its
current luminosity. Combined with previously-determined proper motion and
radial velocity measurements of the cluster, we find that Palomar 13 is on a
highly eccentric orbit ($e\sim 0.8$) with a pericenter of ~9 kpc and an
apocenter of ~69 kpc, and a recent pericentric passage of the cluster ~75 Myr
ago. We note a prominent linear structure in the interstellar dust map that
runs parallel to the candidate tidal features, but conclude that reddening due
to dust is unlikely to account for the structure that we observe. If confirmed,
the Palomar 13 stellar stream would be one of very few streams with a known
progenitor system, making it uniquely powerful for studying the disruption of
globular clusters, the formation of the stellar halo, and the distribution of
matter within our Galaxy.
