Abstract
New photometric and spectroscopic observations of galaxies in the direction of the galaxy cluster LCDCS0001 are presented. The observations were carried out with the Gemini Multi-Object Spectrograph attached to the Gemini South telescope. The main goal of this work is to study the photometric properties and the stellar population of cluster galaxies at the redshift 0.7.
The i' and r' images centered on the cluster coordinates have a field of 5×5. Using the SExtractor program (Bertin & Arnouts 1996, AAS, 117, 393) we have identified in this field around 900 objects with nonstellar brightness profiles. GIM2D (Simard et al. 2002, ApJS, 16, 1) was used to determine the integrated i' magnitudes and to fit a two-dimensional bulge+disc model to the surface brightness distribution of the objects. We found that 54 of these objects are disc-like galaxies.
The projected number density of galaxies is described by a King law up to a radius of 70, which corresponds to a physical scale of 380. Spectra were obtained using two slit masks for 40 objects distributed throughout the field. We obtain redshifts for 24 galaxies spanning the range 0.19< z <0.79. The radial velocity distribution of these galaxies is strongly concentrated at z = 0.7, thus confirming the photometric redshift estimated for this cluster.
12 objects are confirmed as cluster members, since their velocity offset to the mean cluster redshift is kmsec. The stellar population ages and metallicities of the cluster members were estimated by a population synthesis method using as basis the Bruzual & Chariot (2003, MNRAS, 344, 1000) spectrophotometric models.