Red Clump stars in the Bootes III stellar system

M. Correnti, M. Bellazzini, F. R. Ferraro

Published 2009-04-20Version 1

We report on the detection of a population of Red Clump (RC) stars probably associated with the recently discovered stellar system Bootes III. The RC is identified as a 3 sigma peak in the Luminosity Function (LF) of colour-selected stars extracted from the SDSS database. The peak is consistently detected in the g,r,i and z LFs at the expected luminosity of a typical RC at the distance of Bootes III. Moreover the stars around the LF peak show a maximum of surface density nearly coincident with the reported center of the system. Assuming that the detected feature is the genuine RC of Bootes III, we find that the system has the HB morphology typical of old and metal-poor dwarf spheroidals, it has an integrated magnitude M_V=-5.8 pm 0.5 and an ellipticity epsilon about 0.5, quite typical of the recently identified new class of very faint dwarf galaxies.