Abundance segregation in Virgo spiral galaxies

Laboratório de Análise Numérica e Astrofísica, Departamento de Matemática, Universidade Federal de Santa Maria, 97119-900 Santa Maria, RS, Brazil e-mail: oli@lana.ccne.ufsm.br

Received: 25 November 2005
Accepted: 27 February 2006

Abstract

Aims.To derive O/H, N/O, and S/O abundances of regions located in nine Virgo spiral galaxies, as well as to verify what is the cause of the abundance segregation found.

Methods.We employed photoionization models to reproduce observed emission-line intensities of  regions located in the galaxies considered. The abundance gradients obtained were interpreted using a grid of chemical evolution models.

Results.Our models indicate that galaxies near to the core of the Virgo cluster are overabundant in O/H, N/O, and S/O by about 0.25 dex in comparison to the ones at the periphery. With one exception, models with upper stellar mass limit of M_u = 30–40  and age of the ionizing star cluster ranging from 1.5 to 2.5 Myr were able to reproduce the observational data. Chemical models indicate the collapse time-scale for inner regions of galaxies near to the Virgo core is larger than the one in galaxies located at the intermediate and peripheral positions in the cluster, what can be due to the dense environment existing in Virgo Cluster core.