EDP Sciences
Free access
Volume 435, Number 3, June I 2005
Page(s) 871 - 874
Section Galactic structure, stellar clusters and populations
DOI http://dx.doi.org/10.1051/0004-6361:20042538

A&A 435, 871-874 (2005)
DOI: 10.1051/0004-6361:20042538

Discovery of a stellar system in the background of 47 Tucanae

A new cluster of the Small Magellanic Cloud?
M. Bellazzini1, E. Pancino1 and F. R. Ferraro2

1  INAF - Osservatorio Astronomico di Bologna via Ranzani 1, 40127, Bologna, Italy
    e-mail: [michele.bellazzini;elena.pancino]@bo.astro.it
2  Università di Bologna, Dipartimento di Astronomia, via Ranzani 1, 40127, Bologna, Italy
    e-mail: francesco.ferraro3@unibo.it

(Received 14 December 2004 / Accepted 6 February 2005 )

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 $D\simeq 30\arcsec$, is partially resolved into stars on the available CCD images, reaching a limiting magnitude of $V\sim 22.5$, 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.

Key words: Galaxy: globular clusters: individual: Bo A -- galaxies: Local Group

SIMBAD Objects

© ESO 2005