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

• Published in: arXiv.org
• Main Authors: Kundu, A, Majewski, S R, Rhee, J, Rocha-Pinto, H J, Polak, A A, Slesnick, C L, Kunkel, W E, Johnston, K V, Patterson, R J, Geisler, D, Gieren, W, Seguel, J, Smith, V V, Palma, C, Arenas, J, Crane, J D, Hummels, C B
• Format: Paper
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 14.08.2002
• Subjects: Dwarf galaxies; Galaxies; Giant stars; Photometry; Spheroidal galaxies; Stars; Substructures
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.0208276

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.