Robust automatic photometry of local galaxies from SDSS Dissecting the
  color magnitude relation with color profiles
  We present an automatic procedure to perform reliable photometry of galaxies
on SDSS images. We selected a sample of 5853 galaxies in the Coma and Virgo
superclusters. For each galaxy, we derive Petrosian g and i magnitudes, surface
brightness profiles and color profiles. Unlike the SDSS pipeline, our procedure
is not affected by the well known shredding problem and efficiently extracts
Petrosian magnitudes for all galaxies. Hence we derived magnitudes even from
the population of galaxies missed by the SDSS that represents 25% of all Local
supercluster galaxies and ~95% of galaxies with g < 11 mag. After correcting
the g and i magnitudes for Galactic and internal extinction, the blue and red
sequences in the color magnitude diagram are well separated, with similar
slopes. In addition, we study (i) the color-magnitude diagrams in different
galaxy regions, the inner (r <= 1 kpc), intermediate (0.2R{Pet} <=r<=
0.3R{Pet}) and outer, disk-dominated (r>=0.35R{Pet})) zone, and (ii), we
compute template color profiles, discussing the dependences of the templates on
the galaxy masses and on their morphological type. The two analyses
consistently lead to a picture where elliptical galaxies show no color
gradients, irrespective of their masses. Spirals, instead, display a steeper
gradient in their color profiles with increasing mass, consistently with the
growing relevance of a bulge and/or a bar component above 10^{10} Modot.
