Do observed metallicity gradients of early-type galaxies support a hybrid formation scenario?

Ogando, R
Maia, M A G
Chiappini, C
Pellegrini, P S S
Schiavon, R P
Da Costa, L N

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Publication date

September 2005

DOI

10.1086/497824

ISSN

0004-637X

Citation count (estimate)

Abstract

We measure radial gradients of the Mg2 index in 15 E-E/S0 and 14 S0 galaxies. Our homogeneous data set covers a large range of internal stellar velocity dispersions (2.0<logsigma<2.5) and Mg2 gradients (dMg2/dlogr/re* up to -0.14mag/dex). We find for the first time, a noticeable lower boundary in the relation between Mg2 gradient and sigma along the full range of sigma, which may be populated by galaxies predominantly formed by monolithic collapse. At high sigma, galaxies showing flatter gradients could represent objects which suffered either important merging episodes or later gas accretion. These processes contribute to the flattening of the metallicity gradients and their increasing importance could define the distribution of the objects...