The Geometry of Sagittarius Stream from Pan-STARRS1 3π RR Lyrae

We present an analysis of the Sagittarius (Sgr) stellar stream's 3D geometry, based on the sample of ̃44 000 RR Lyrae (RRab) stars from the Pan-STARRS1 (PS1) 3π survey, extending to ≳120 kpc with a distance precision of ̃ 3%. A projection of RR Lyrae stars within |\tilde{B}|_{☉}<9° of the Sgr stream's orbital plane reveals the morphology of both the leading and the trailing arms at very high contrast. We fit a model for the angular mean distance and line-of-sight depth, resulting in estimates of the mean stream distance precise to ̃1% and resolving the stream's line-of-sight depth. These improved geometric constraints can serve as new restrictions for dynamical stream models