  Stars that escape globular clusters form tidal tails that are predominantly
shaped by the global distribution of mass in the Galaxy, but also preserve a
historical record of small-scale perturbations. Using deep $grz$ photometry
from DECaLS, we present highly probable members of the tidal tails associated
with the disrupting globular cluster Palomar 5. These data yield the cleanest
view of a stellar stream beyond $\sim20\,\rm kpc$ and reveal: (1) a wide, low
surface-brightness extension of the leading tail; (2) significant density
variations along the stream; and (3) sharp changes in the direction of both the
leading and the trailing tail. In the fiducial Milky Way model, a rotating bar
perturbs the Palomar 5 tails and can produce streams with similar width and
density profiles to those observed. However, the deviations of the stream track
in this simple model do not match those observed in the Palomar 5 trailing
tail, indicating the need for an additional source of perturbation. These
discoveries open up the possibility of measuring the population of perturbers
in the Milky Way, including dark-matter subhalos, with an ensemble of stellar
streams and deep photometry alone.
