2001/01/31 by Claudia Maraston, C. Maraston, M. Kissler‐Patig +5 · 2 citations
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Asymptotic giant branch #Galaxies: Formation, Evolution, Phenomena #Galaxy #Large Magellanic Cloud #Metallicity #Photometry (optics) #Physics #Population #Star cluster #Star formation #Stars #Stellar population #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1051/0004-6361:20010189
Accepted for publication in Astronomy & Astrophysics, 17 pages, 12 figures
arxiv created 2001/01/31 · openalex publication_date 2001/04/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We have extended the study of the young star clusters observed in the merger remnant galaxy NGC 7252 by obtaining K band photometry for these clusters. Our K band data significantly complement the optical photometry and spectroscopy in the literature: K band data are fundamental to study the Asymptotic Giant Branch (AGB) population of these clusters, since the AGB phase transition (occuring between the age of ~200 Myr and ~1 Gyr) causes abrupt changes in the near-infrared luminosity of the clusters while producing only small changes in the optical. Therefore, the e.g. colour is ideal to study this evolutionary phase of stellar populations. For the present analysis we present models for Simple Stellar Populations which include the contribution of the AGB stellar phase, calibrated with the young and intermediate age star clusters of the Magellanic Clouds. The comparison with the colour distribution of the NGC 7252 star clusters shows that they are indeed intermediate age clusters undergoing the AGB phase transition. The AGB phase transition is observed for the first time outside the Local Group. Most of the studied clusters span the very narrow age range Myr, and likely have metallicities 0.5-. A very important exception is the cluster W32, which has already completed its AGB epoch, its colours being consistent with an age of ~1-2 Gyr. This impacts on the duration of the merger-induced starburst. The strengths of the magnesium and iron lines in the spectrum of the best observed cluster W3, and in the spectrum of the diffuse central light of NGC 7252, do not show an overabundance in α-elements, in contrast to the bulk stellar population of elliptical galaxies.