Feeling the pull, a study of natural Galactic accelerometers. I: photometry of the delicate stellar stream of the Palomar 5 globular cluster

TL;DR

This study uses deep photometric data to analyze the stellar stream of Palomar 5, finding minimal sub-structure and providing detailed distance mapping, which informs models of dark matter sub-halos in the Galactic halo.

Contribution

It offers the first detailed wide-field photometric analysis of Palomar 5's stream, challenging previous findings of sub-structure and providing precise distance measurements.

Findings

No significant gaps or under-densities detected in the stream.

Only one notable over-density found, contrary to earlier SDSS-based studies.

Created the deepest wide-field map of the Palomar 5 system to date.

Abstract

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 DDO51 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 under-densities, and find only a single significant over-density. 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 sub-structure 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.