Exploring Halo Substructure with Giant Stars III: First Results from the Grid Giant Star Survey and Discovery of a Possible Nearby Sagittarius Tidal Structure in Virgo

Abstract

We describe first results of a spectroscopic probe of selected fields from the Grid Giant Star Survey. Multifiber spectroscopy of several hundred stars in a strip of eleven fields along delta approximately -17^{circ}, in the range 12 <~ alpha <~ 17 hours, reveals a group of 8 giants that have kinematical characteristics differing from the main field population, but that as a group maintain coherent, smoothly varying distances and radial velocities with position across the fields. Moreover, these stars have roughly the same abundance, according to their MgH+Mgb absorption line strengths. Photometric parallaxes place these stars in a semi-loop structure, arcing in a contiguous distribution between 5.7 and 7.9 kpc from the Galactic center. The spatial, kinematical, and abundance coherence of these stars suggests that they are part of a diffuse stream of tidal debris, and one roughly consistent with a wrapped, leading tidal arm of the Sagittarius dwarf spheroidal galaxy.

arXiv comment8 pages including 4 figures. Accepted for publication in ApJL

References in corpus (20)

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Cited by in corpus (19)

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• The Sagittarius Dwarf Galaxy: a Model for Evolution in a Triaxial Milky Way Halo
• A Low Latitude Halo Stream around the Milky Way
• A 2MASS All-Sky View of the Sagittarius Dwarf Galaxy: IV. Modeling the Sagittarius Tidal Tails
• Tracing out the Northern Tidal Stream of the Sagittarius Dwarf Spheoridal Galaxy
• Draco -- A Failure of the Tidal Model
• The Virgo stellar over-density: Mapping the infall of the Sagittarius tidal stream onto the Milky Way disk
• Blue Horizontal Branch Stars in the Sagittarius dwarf spheroidal galaxy
• Cool carbon stars in the halo: a new survey based on 2MASS
• Proper Motions in Kapteyn Selected Area 103: A Preliminary Orbit for the Virgo Stellar Stream
• Surveying the Inner Halo of the Galaxy with 2MASS-Selected Horizontal Branch Candidates
• Exploring the Sagittarius Stream with SEKBO Survey RR Lyrae Stars
• Spatial and Velocity clumping in an SDSS blue horizontal branch star catalogue
• The Millennium Galaxy Catalogue: Star counts and the Structure of the Galactic Stellar Halo
• Fluorine Abundances in the Galactic Disk
• Deep Chandra observations of X-ray point sources in M87
• Probing the Sagittarius stream with blue horizontal branch stars
• The Fan Observatory Bench Optical Spectrograph (FOBOS)
• SiO Maser Survey towards off-plane O-rich AGBs around the orbital plane of the Sagittarius Stellar Stream