Hunting the most distant stars in the Milky Way: methods and initial results
- Haverford College, 370 Lancaster Avenue, Haverford, PA 19041 (United States)
- Department of Astronomy, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States)
- Michigan State Astronomy Group, Michigan State University, Biomedical Physical Sciences Building, 567 Wilson Road, Room 3261, East Lansing, MI 48824-2320 (United States)
We present a new catalog of 404 M giant candidates found in the UKIRT Infrared Deep Sky Survey (UKIDSS). The 2400 deg{sup 2} available in the UKIDSS Large Area Survey Data Release 8 resolve M giants through a volume four times larger than that of the entire Two Micron All Sky Survey. Combining near-infrared photometry with optical photometry and proper motions from the Sloan Digital Sky Survey yields an M giant candidate catalog with less M dwarf and quasar contamination than previous searches for similarly distant M giants. Extensive follow-up spectroscopy of this sample will yield the first map of our Galaxy's outermost reaches over a large area of sky. Our initial spectroscopic follow-up of ∼30 bright candidates yielded the positive identification of five M giants at distances ∼20-90 kpc. Each of these confirmed M giants have positions and velocities consistent with the Sagittarius stream. The fainter M giant candidates in our sample have estimated photometric distances ∼200 kpc (assuming [Fe/H] = 0.0), but require further spectroscopic verification. The photometric distance estimates extend beyond the Milky Way's virial radius, and increase by ∼50% for each 0.5 dex decrease in assumed [Fe/H]. Given the number of M giant candidates, initial selection efficiency, and volume surveyed, we loosely estimate that at least one additional Sagittarius-like accretion event could have contributed to the hierarchical build-up of the Milky Way's outer halo.
- OSTI ID:
- 22340311
- Journal Information:
- Astronomical Journal (New York, N.Y. Online), Vol. 147, Issue 4; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1538-3881
- Country of Publication:
- United States
- Language:
- English
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