A wide-area view of the Phoenix dwarf galaxy from VLT/FORS imaging
  We present results from a wide-area photometric survey of the Phoenix dwarf
galaxy, one of the rare dwarf irregular/ dwarf spheroidal transition type
galaxies (dTs) of the Local Group (LG). These objects offer the opportunity to
study the existence of possible evolutionary links between the late- and early-
type LG dwarf galaxies, since the properties of dTs suggest that they may be
dwarf irregulars in the process of transforming into dwarf spheroidals. Using
FORS at the VLT we have acquired VI photometry of Phoenix. The data reach a
S/N~10 just below the horizontal branch of the system and consist of a mosaic
of images that covers an area of 26' x 26' centered on the coordinates of the
optical center of the galaxy. Examination of the colour-magnitude diagram and
luminosity function revealed the presence of a bump above the red clump,
consistent with being a red giant branch bump. The deep photometry combined
with the large area covered allows us to put on a secure ground the
determination of the overall structural properties of the galaxy and to derive
the spatial distribution of stars in different evolutionary phases and age
ranges, from 0.1 Gyr to the oldest stars. The best-fitting profile to the
overall stellar population is a Sersic profile of Sersic radius R_S =
1.82'+-0.06' and m=0.83+-0.03. We confirm that the spatial distribution of
stars is found to become more and more centrally concentrated the younger the
stellar population, as reported in previous studies. This is similar to the
stellar population gradients found for close-by Milky Way dwarf spheroidal
galaxies. We quantify such spatial variations by analyzing the surface number
density profiles of stellar populations in different age ranges; [Abridged]
