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Seminars at FGG

Deep LBT photometry of VV124: an isolated dwarf galaxy falling into the Local Group

Speaker: Michele Bellazzini (INAF - Osservatorio Astronomico di Bologna)

Date and time: 2009-09-23 11:00

Abstract VV124 = UGC4879 has been recently recognized as a dwarf galaxy lying in the outskirts of the Local Group (Kopylov et al. 2008). I present the preliminary results from our very deep LBT observations of this galaxy. We derived a Color-Magnitude diagram reaching r=26.5, down to ~4 mag below the RGB Tip and more than two magnitude deeper than previously available photometries. We obtain a very clean detection of the RGB tip, deriving a distance of 1.3 Mpc. Our CMD reveals that the galaxy is dominated by an old and metal-poor population, and it displays a metallicity gradient; a tentative detection of and extended HB and RR Ly population is also obtained. Coupling surface photometry and star-counts we are able to trace the Surface Brightness profile of the galaxy out to ~5' (=2 kpc), that is 5 times more extended than previous studies. We provide some interesting evidences suggesting that VV124 is a good representative of the pristine status of dwarf Spheroidal galaxies, before that close interactions with the main galaxy they are orbiting around transformed them into the very Low SB system we observe today.