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Title: Discovery of star formation in the extreme outer galaxy possibly induced by a high-velocity cloud impact

We report the discovery of star formation activity in perhaps the most distant molecular cloud in the extreme outer galaxy. We performed deep near-infrared imaging with the Subaru 8.2 m telescope, and found two young embedded clusters at two CO peaks of 'Digel Cloud 1' at the kinematic distance of D = 16 kpc (Galactocentric radius R {sub G} = 22 kpc). We identified 18 and 45 cluster members in the two peaks, and the estimated stellar densities are ∼5 and ∼3 pc{sup –2}, respectively. The observed K-band luminosity function suggests that the age of the clusters is less than 1 Myr and also that the distance to the clusters is consistent with the kinematic distance. On the sky, Cloud 1 is located very close to the H I peak of high-velocity cloud Complex H, and there are some H I intermediate velocity structures between the Complex H and the Galactic disk, which could indicate an interaction between them. We suggest the possibility that Complex H impacting on the Galactic disk has triggered star formation in Cloud 1 as well as the formation of the Cloud 1 molecular cloud.
Authors:
; ;  [1] ;  [2] ;  [3] ;  [4]
  1. Institute of Astronomy, School of Science, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan)
  2. Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)
  3. Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)
  4. National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)
Publication Date:
OSTI Identifier:
22370294
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 795; 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; CARBON MONOXIDE; COSMIC GASES; DENSITY; GALAXIES; GALAXY CLUSTERS; INTERACTIONS; LUMINOSITY; MOLECULES; STARS; TELESCOPES; VELOCITY