Interpreting Debris from Satellite Disruption in External Galaxies

We examine the detectability and interpretation of debris trails caused bysatellite disruption in external galaxies using semi-analytic approximationsfor the dependence of streamer length, width and surface brightness onsatellite and primary galaxy characteristics. The semi-analytic method istested successfully against N-body simulations and then applied to threerepresentative astronomical applications. First, we show how streamerproperties can be used to estimate mass-to-light ratios $\Upsilon$ and streamerages of totally disrupted satellites, and apply the method to the stellar arcin NGC 5907. Second, we discuss how the lack of observed tidal debris around asatellite can provide an upper limit on its mass-loss rate, and, as an example,derive the implied limits on mass-loss rates for M32 and NGC 205 aroundAndromeda. Finally, we point out that a statistical analysis of streamerproperties might be applied to test and refine cosmological models ofhierarchical galaxy formation, and use the predicted debris from a standard$\Lambda$CDM realization to test the feasibility of such a study. Using theLocal Group satellites and the few known examples of debris trails in theGalaxy and in external systems, we estimate that the best current techniquescould characterize the brightest ($R < 29$ mag/ arcsec$^{2}$) portions of theyoungest (3 dynamical periods) debris streamers. If systematics can becontrolled, planned large-aperture telescopes such as CELT and OWL may allowfainter trails to be detected routinely and thus used for statistical studiessuch as those required for tests of galaxy formation.Comment: 33 pages, 8 figures. Revised version, accepted for publication in Ap