The $>100$ kpc Distant Spur of the Sagittarius Stream and the Outer Virgo Overdensity, as Seen in PS1 RR Lyrae Stars

Abstract

We report the detection of spatially distinct stellar density features near the apocenters of the Sagittarius (Sgr) stream's main leading and trailing arm. These features are clearly visible in a high-fidelity stellar halo map that is based on RR Lyrae from Pan-STARRS1: there is a plume of stars 10 kpc beyond the apocenter of the leading arm, and there is a "spur" extending to 130 kpc, almost 30 kpc beyond the previously detected apocenter of the trailing arm. Such apocenter substructure is qualitatively expected in any Sgr stream model, as stars stripped from the progenitor at different pericenter passages become spatially separated there. The morphology of these new Sgr stream substructures could provide much-needed new clues and constraints for modeling the Sgr system, including the level of dynamical friction that Sgr has experienced. We also report the discovery of a new, presumably unrelated halo substructure at 80 kpc from the Sun and $10^{\circ }$ from the Sgr orbital plane, which we dub the Outer Virgo Overdensity.

Accepted to ApJ Letters, this is Branimir Sesar's last paper in astronomy and he would like to thank his friends and colleagues for supporting him during the last 15 years

References in corpus (6)

• "Skinny Milky Way, Please", says Sagittarius
• Detection of a 60 Degree-Long Dwarf Galaxy Debris Stream
• Globular Cluster Streams as Galactic High-Precision Scales - The Poster Child Palomar 5
• Discovery of a New, Polar-Orbiting Debris Stream in the Milky Way Stellar Halo
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Cited by in corpus (16)

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• The Zwicky Transient Facility Catalog of Periodic Variable Stars
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• The Geometry of Sagittarius Stream from Pan-STARRS1 3$\pi$ RR Lyrae
• An all-sky proper motion map of the Sagittarius stream using Gaia DR2
• Quantifying the Stellar Halo's Response to the LMC's Infall with Spherical Harmonics
• The effects of dynamical substructure on Milky Way mass estimates from the high velocity tail of the local stellar halo
• Kinematics of the Palomar 5 stellar stream from RR Lyrae stars
• Tracing Kinematic and Chemical Properties of Sagittarius Stream by K-Giants, M-Giants, and BHB stars
• The Outer Halo of the Milky Way as Probed by RR Lyr Variables from the Palomar Transient Facility
• Detecting the Sagittarius stream with LAMOST DR4 M giants \& Gaia DR2
• To the Galactic Virial Radius with Hyper Suprime-Cam
• The Pristine survey -- VII. A cleaner view of the Galactic outer halo using blue horizontal branch stars
• The course of the Orphan Stream in the Northern Galactic Hemisphere traced with Gaia DR2
• Empirical completeness assessment of the Gaia DR2, Pan-STARRS 1 and ASAS-SN-II RR Lyrae catalogues
• A catalogue of oxygen-rich pulsating giants in the galactic halo and the Sagittarius stream