Spectroscopic Confirmation of the Pisces Overdensity
Abstract
We present spectroscopic confirmation of the "Pisces Overdensity," also known as "Structure J," a photometric overdensity of RR Lyrae stars discovered by the Sloan Digital Sky Survey at an estimated photometric distance of ~85 kpc. We measure radial velocities for eight RR Lyrae stars within Pisces. We find that five of the eight stars have heliocentric radial velocities within a narrow range of -87 km s-1 < vr < -67 km s-1, suggesting that the photometric overdensity is mainly due to a physically associated system, probably a dwarf galaxy or a disrupted galaxy. Two of the remaining three stars differ from one another by only 9 km s-1, but it would be premature to identify them as a second system.
This Letter includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 2009
- DOI:
- 10.1088/0004-637X/705/2/L158
- arXiv:
- arXiv:0908.1381
- Bibcode:
- 2009ApJ...705L.158K
- Keywords:
-
- galaxies: dwarf;
- Galaxy: halo;
- Galaxy: structure;
- stars: individual: RR Lyrae;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 8 pages including 4 figures