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Title: THE MOST DISTANT STARS IN THE MILKY WAY

We report on the discovery of the most distant Milky Way (MW) stars known to date: ULAS J001535.72+015549.6 and ULAS J074417.48+253233.0. These stars were selected as M giant candidates based on their infrared and optical colors and lack of proper motions. We spectroscopically confirmed them as outer halo giants using the MMT/Red Channel spectrograph. Both stars have large estimated distances, with ULAS J001535.72+015549.6 at 274 ± 74 kpc and ULAS J074417.48+253233.0 at 238 ± 64 kpc, making them the first MW stars discovered beyond 200 kpc. ULAS J001535.72+015549.6 and ULAS J074417.48+253233.0 are both moving away from the Galactic center at 52 ± 10 km s{sup –1} and 24 ± 10 km s{sup –1}, respectively. Using their distances and kinematics, we considered possible origins such as: tidal stripping from a dwarf galaxy, ejection from the MW's disk, or membership in an undetected dwarf galaxy. These M giants, along with two inner halo giants that were also confirmed during this campaign, are the first to map largely unexplored regions of our Galaxy's outer halo.
Authors:
;  [1] ; ;  [2] ;  [3] ;  [4] ;  [5]
  1. Haverford College, 370 Lancaster Ave, Haverford, PA 19041 (United States)
  2. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)
  3. Kapteyn Astronomical Institute, P.O. Box 800, 9700 AV Groningen (Netherlands)
  4. Department of Astronomy, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States)
  5. 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:
22365575
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 790; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTROPHYSICS; COLOR; DISTANCE; INFRARED RADIATION; MILKY WAY; STARS