RT Journal Article T1 On the environmental dependence of the cluster galaxy assembly timescale A1 Carretero, C. A1 Vazdekis, A. A1 Beckman, J. E. A1 Sánchez Blázquez, Patricia A1 Gorgas García, Francisco Javier AB We present estimates of CN and Mg overabundances with respect to Fe for early-type galaxies in eight clusters over a range of richness and morphology. Spectra were taken from the Sloan Digital Sky Survey Data Release 1 and from William Hershel Telescope and Centro Astronómico Hispano-Alemán observations. Abundances were derived from absorption lines and single-burst population models, by comparing galaxy spectra with appropriately broadened synthetic model spectra. We detect correlations between the [Mg/CN] and [CN/Fe] values and the cluster X-ray luminosity. No correlation is observed for [Mg/Fe]. We also see a clear trend in the richness and morphology of the clusters. This is interpreted as giving varying formation timescales for CN, Mg, and Fe and a varying star formation history in early-type galaxies as a function of their environment: intermediate-mass early-type galaxies in more massive clusters are assembled on shorter timescales than in less massive clusters, with an upper limit of ~1 Gyr. PB American Astronomical Society SN 0004-637X YR 2004 FD 2004-07-10 LK https://hdl.handle.net/20.500.14352/51838 UL https://hdl.handle.net/20.500.14352/51838 LA eng NO © 2004. The American Astronomical Society. All rights reserved. The authors thank A. Aguerri, X. Barcons, L. Carigi, C. Gutiérrez, R. Peletier, and the anonymous referee for useful comments. We acknowledge grant AYA2001-0435 from the Spanish Ministry of Science and Technology. The SDSS is managed by the ARC for the Participating Institutions. NO Ministerio de Ciencia y Tecnología (MCYT), España DS Docta Complutense RD 31 dic 2025