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
/ Authors
A. Kundu, S. Majewski, S. Majewski, J. Rhee, H. Rocha-Pinto, A. Polak, C. Slesnick, W. Kunkel, Kathryn V. Johnston, R. Patterson
and 8 more authors
Doug Geisler, W. Gieren, J. Seguel, V. Smith, C. Palma, J. Arenas, Jeffrey D. Crane, C. Hummels
/ 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 11 fields along δ ≈ -17°, in the range 12 hr ≲ α ≲ 17 hr, reveals a group of eight 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 semiloop 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.
Journal: The Astrophysical Journal Letters
DOI: 10.1086/343728