The Red Giant Branch Tip and Bump of the Leo II dwarf spheroidal galaxy

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Abstract
We present V and I photometry of a 9.4' X 9.4' field centered on the dwarf spheroidal galaxy Leo II. The Tip of the Red Giant Branch is identified at I^{TRGB}=17.83 +/- 0.03 and adopting <[M/H]> = -1.53 +/- 0.2 from the comparison of RGB stars with Galactic templates, we obtain a distance modulus (m-M)_0=21.84 +/- 0.13, corresponding to a distance D=233 +/- 15 Kpc. Two significant bumps have been detected in the Luminosity Function of the Red Giant Branch. The fainter bump (B1, at V=21.76 +/- 0.05) is the RGB bump of the dominant stellar population, while the actual nature of the brightest one (B2, at V=21.35 +/- 0.05) cannot be firmly assessed on the basis of the available data, it can be due to the Asymptotic Giant Branch Clump of the main population or it may be a secondary RGB bump. The luminosity of the main RGB bump (B1) suggests that the majority of RGB stars in Leo II belongs to a population that is ~4 gyr younger than the classical Galactic globular clusters. The stars belonging to the He-burning Red Clump are shown to be significantly more centrally concentrated than RR Lyrae and Blue Horizontal Branch stars, probing the existence of an age/metallicity radial gradient in this remote dwarf spheroidal.

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