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Title: Hunting the most distant stars in the Milky Way: methods and initial results

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 selectionmore » 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.« less
Authors:
;  [1] ;  [2] ; ;  [3]
  1. Haverford College, 370 Lancaster Avenue, Haverford, PA 19041 (United States)
  2. Department of Astronomy, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States)
  3. Michigan State Astronomy Group, Michigan State University, Biomedical Physical Sciences Building, 567 Wilson Road, Room 3261, East Lansing, MI 48824-2320 (United States)
Publication Date:
OSTI Identifier:
22340311
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astronomical Journal (New York, N.Y. Online); Journal Volume: 147; Journal Issue: 4; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CATALOGS; CONTAMINATION; DISTANCE; DWARF STARS; EFFICIENCY; INFRARED SPECTRA; MILKY WAY; PHOTOMETRY; PROPER MOTION; QUASARS; SKY; SPECTROSCOPY; STARS; STREAMS; VELOCITY; VERIFICATION