FEELING THE PULL: A STUDY OF NATURAL GALACTIC ACCELEROMETERS. I. PHOTOMETRY OF THE DELICATE STELLAR STREAM OF THE PALOMAR 5 GLOBULAR CLUSTER

We present an analysis of wide-field photometric surveys of the Palomar 5 globular cluster and its stellar stream, based on g ?> - and r ?> -band measures together with narrow-band DDO 51 photometry. In this first study, we use the deep (g, r) data to measure the incidence of gaps and peaks along the stream. Examining the star-counts profile of the stream plus contaminating populations, we find no evidence for significant underdensities, and find only a single significant overdensity. This is at odds with earlier studies based on matched-filter maps derived from shallower SDSS data if the contaminating population possesses plausible spatial properties. The lack of substantial substructure along the stream may be used in future dynamical simulations to examine the incidence of dark matter sub-halos in the Galactic halo. We also present a measurement of the relative distances along the stream, which we use to create the deepest wide-field map of this system to date.