Photometric and spectroscopic study of Abell 0671

Abstract

In this paper, we present a photometric and spectroscopic study of the nearby galaxy cluster Abell 0671 (A671) with 15 intermediate-band filters in the Beijing–Arizona–Taiwan–Connecticut (BATC) system, and using Sloan Digital Sky Survey (SDSS) data. After a cross-identification between the photometric data obtained from the BATC and SDSS, we obtain a list of 985 galaxies down to V∼ 20.0 mag in a field of view of 58 × 58 arcmin2, including 103 spectroscopically confirmed member galaxies. The photometric redshift technique is applied to the galaxy sample to determine further membership. After the colour–magnitude relation is taken into account, 97 galaxies brighter than hBATC= 19.5 mag are selected as new member galaxies. Based on the enlarged sample of cluster galaxies, the spatial distribution and dynamics of A671 are investigated. The substructures of A671 are clearly shown by the sample of bright members. However, the substructures appear less significant based on the enlarged sample, which is mainly a result of larger uncertainties in the line-of-sight velocities of the newly selected faint members. The SDSS r-band luminosity function of A671 is flat at faint magnitudes, with the faint-end slope parameter α=−1.12. The SDSS spectra allow us to investigate the star formation history of bright cluster galaxies. The galaxies in the core region are found to be older than those in the outskirts. No environmental effect is found for metallicities of the early-type galaxies (ETGs). Both mean stellar ages and metallicities in the bright member galaxies are found to be correlated strongly with their stellar masses assembled, and such correlations are dependent upon morphology. The positive correlation between age and stellar mass supports the downsizing scenario. By comparing the absorption-line indices of ETGs with state-of-the-art stellar population models, we derive the relevant parameters of the simple stellar population (such as age, [Fe/H], [Mg/Fe], [C/Fe], [N/Fe] and [Ca/Fe]). The ETGs at the cluster centre tend to have smaller Hβ indices, indicating that central ETGs are likely to be older. The distribution of the total metallicity indicator, [MgFe]′, does not show any environmental effects. The relations between the simple stellar population parameters and the velocity dispersion in A671 are in good agreement with previous studies.