We report on the discovery of a stellar system in the background of the Galactic globular cluster 47 Tucanae (NGC 104), located 14.8 arcmin North-West of the cluster center. The object, whose apparent diameter is D≃ 30 arcsec, is partially resolved into stars on the available CCD images, reaching a limiting magnitude of V~ 22.5, and is detected as a significant (more than 5 sigma) overdensity of blue stars (B-V<0.7). The color magnitude diagram of the system, its characteristic projected size and its position in the sky suggest that it is an intermediate-old age cluster belonging to the Small Magellanic Cloud, whose outskirts lie in the background of 47 Tuc. Although less likely, the possibility that the object is an unknown dwarf galaxy in the outskirts of the Local Group cannot completely be ruled out by the present data.
Bellazzini M., Pancino E., Ferraro F. R. (2005). Discovery of a stellar system in the background of 47 Tucanae. A new cluster of the Small Magellanic Cloud?. ASTRONOMY & ASTROPHYSICS, 435, 871-874 [10.1051/0004-6361:20042538].
Discovery of a stellar system in the background of 47 Tucanae. A new cluster of the Small Magellanic Cloud?
FERRARO, FRANCESCO ROSARIO
2005
Abstract
We report on the discovery of a stellar system in the background of the Galactic globular cluster 47 Tucanae (NGC 104), located 14.8 arcmin North-West of the cluster center. The object, whose apparent diameter is D≃ 30 arcsec, is partially resolved into stars on the available CCD images, reaching a limiting magnitude of V~ 22.5, and is detected as a significant (more than 5 sigma) overdensity of blue stars (B-V<0.7). The color magnitude diagram of the system, its characteristic projected size and its position in the sky suggest that it is an intermediate-old age cluster belonging to the Small Magellanic Cloud, whose outskirts lie in the background of 47 Tuc. Although less likely, the possibility that the object is an unknown dwarf galaxy in the outskirts of the Local Group cannot completely be ruled out by the present data.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
