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Robust automatic photometry of local galaxies from SDSS. Dissecting the color magnitude relation with color profiles.

Consolandi, Guido and Gavazzi, Giuseppe and Fumagalli, Michele and Dotti, Massimo and Fossati, Matteo (2016) 'Robust automatic photometry of local galaxies from SDSS. Dissecting the color magnitude relation with color profiles.', Astronomy & astrophysics., 591 . A38.


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 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 which 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 (0.2RPet ≤ r ≤ 0.3RPet) and outer, disk-dominated (r ≥ 0.35RPet)) 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, which is consistent with the growing relevance of a bulge and/or a bar component above 1010 M⊙.

Item Type:Article
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Publisher statement:Reproduced with permission from Astronomy & Astrophysics, © ESO, 2016
Date accepted:23 March 2016
Date deposited:07 July 2016
Date of first online publication:08 June 2016
Date first made open access:07 July 2016

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