Exposing Sgr tidal debris behind the Galactic disk with M giants selected in WISE$\cap$2MASS

Abstract

We show that a combination of infrared photometry from WISE and 2MASS surveys can yield highly pure samples of M giant stars. We take advantage of the new WISE$\cap$2MASS M giant selection to trace the Sagittarius trailing tail behind the Galactic disk in the direction of the anti-centre. The M giant candidates selected via broad-band photometry are confirmed spectroscopically using AAOmega on the AAT in 3 fields around the extremity of the Sgr trailing tail in the Southern Galactic hemisphere. We demonstrate that at the Sgr longitude ${\tilde{\Lambda }}_{\odot }=204^{\circ }$, the line-of-sight velocity of the trailing tail starts to deviate from the track of the Law & Majewski (2010) model, confirming the prediction of Belokurov et al. (2014). This discovery serves to substantiate the measurement of low differential orbital precession of the Sgr stream which in turn may imply diminished dark matter content within 100 kpc.

8 pages, 7 figures; submitted to MNRAS, first referee report received

References in corpus (6)

• The UKIRT Infrared Deep Sky Survey (UKIDSS)
• "Skinny Milky Way, Please", says Sagittarius
• Tracing Sagittarius Structure with SDSS and SEGUE Imaging and Spectroscopy
• TriAnd and its Siblings: Satellites of Satellites in the Milky Way Halo
• Exploring Halo Substructure with Giant Stars: The Nature of the Triangulum-Andromeda Stellar Features
• Sagittarius stream 3-d kinematics from SDSS Stripe 82

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• Detecting the Sagittarius stream with LAMOST DR4 M giants \& Gaia DR2
• The Pristine survey -- VII. A cleaner view of the Galactic outer halo using blue horizontal branch stars
• Hubble Space Telescope Proper Motions of Individual Stars in Stellar Streams: Orphan, Sagittarius, Lethe, and the New "Parallel" Stream
• Potential Black Hole Seeding of the Spiral Galaxy NGC 4424 via an Infalling Star Cluster
• A machine learning approach to photometric metallicities of giant stars
• Atmospheric parameters and kinematic information for the M giants stars from LAMOST DR9