科研之友
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摘要
Using the Sloan Digital Sky Survey (SDSS), 900 deg(2) of the sky surrounding M31 and M33 have been searched for globular clusters (GCs) that through galaxy interaction have become unbound from their parent systems and M31 (hence, intergalactic globular clusters, IGCs). This search reached a maximum of 500 kpc in projected galactocentric distance (R-gc) from M31. Visual examination of 283,871 SDSS cutout images and of 1143 fits images yielded 320 candidates. This sample was reduced to six GCs and one likely candidate by excluding galaxies on the basis of combinations of their optical, ultraviolet, and infrared colors from the SDSS, the Galaxy Evolution Explorer satellite, and the Wide-field Infrared Survey Explorer satellite, as well as their photometric redshifts from the SDSS. Since these seven objects have 14 kpc <= R(g)c <= 137 kpc, they are more likely to be GCs in the halo of M31 than IGCs. They are all "classical" as opposed to "extended" GCs, and they provide further evidence that the remote halo of M31 (R-gc >= 50 kpc) contains more GCs of all types and, in particular, far more "classical" ones than the remote halo of the Milky Way.
- 出版日期2014-4
