An extended star cluster at the outer edge of the spiral galaxy M33

作者：Stonkute Rima^*; Vansevicius Vladas; Arimoto Nobuo; Hasegawa Takashi; Narbutis Donatas; Tamura Naoyuki; Jablonka Pascale; Ohta Kouji; Yamada Yoshihiko

来源：Astronomical Journal, 2008, 135(4): 1482-1487.

DOI：10.1088/0004-6256/135/4/1482

• galaxies : individual (M33)
• galaxies : star clusters

We report the discovery of an extended globular-like star cluster, M33-EC1, at the outer edge of the spiral galaxy M33. The distance to the cluster is 890 kpc, and it lies at a projected distance of 12.5 kpc from the center of M33. Old age (greater than or similar to 7 Gyr) and low metallicity ([M/ H] less than or similar to -1.4) are estimated on the basis of isochrone fits. Color-magnitude diagrams of stars, located in the cluster's area, and photometric and structural parameters of the cluster are presented. The cluster's luminosity (M-V = -6.6) and half-light radius (r(h) = 20.3 pc) are comparable to those of the extended globular clusters, discovered in more luminous Local Group galaxies, the Milky Way and M31. Extended globular clusters are suspected to be remnants of accreted dwarf galaxies, and the finding of such a cluster in the late-type dwarf spiral galaxy M33 would imply a complex merging history in the past.

• 出版日期2008-4
• 单位中国科学院国家天文台