Presentation #402.03 in the session “How Gaia Reveals the Galaxy’s Secrets: Results on the Galactic Scale, Part 2”.
We present new quantification of the radial extent of likely member stars of the Boötes I ultra faint dwarf galaxy, using a combination of Pan-STARRS photometry and Gaia EDR3 proper motions. We have identified new candidate blue horizontal branch and blue straggler star members well beyond the previously determined nominal tidal radius, which was based on model fits to the surface brightness profile. In addition, we take advantage of the improved astrometry of Gaia EDR3 and re-determine the mean proper motion and orbital parameters of the galaxy. We use these orbital parameters in concert with our set of radially extended sources to place new constraints on the total mass and tidal radius of the galaxy.