People involved at OAB: Bellazzini, Origlia, Pancino
The Local Group (LG) of Galaxies is a unique laboratory to study the
properties of the most common types of galaxies in the Universe.
Moreover, it offers the opportunity to calibrate the luminosities of
standard candles - such as Cepheids and RR Lyraes - which can be
used to determine the extragalactic distance scale, hence the value of
and the age of the Universe.
Our programme, aimed at the revision of the distance scale of the Local Group, based on our new RGB tip calibration (Bellazzini, Ferraro & Pancino 2001), is proceeding. We obtained deep photometry for a number of dwarf galaxies and the results of a comparative study of the Ursa Minor and Draco dSph has been completed. The most interesting result is the detection of a striking difference in the structure in these otherwise similar galaxies. In particular, UMi shows up significant sub-structures that may be interpreted as a signature of strong tidal stress.
Our photometric survey of the evolved population of local dwarf galaxies led to the discovery of the RGB bump in a number of dSph galaxies (Sgr, Sex, UMi, Leo II). Such discoveries have opened a new line of research aimed at the interpretation of this observational feature in composite stellar populations, in order to obtain information on the early star formation histories of these galaxies from this new observational constraint (see Bellazzini 2003).
This research is in collaboration with Ferraro and Sabbi (Astron. Dept., University of Bologna), and Oliva (INAF-Arcetri/TNG Obs.).