2008/08/31 by M. S. Clemens, A. Bressan, P. Panuzzo +4 · 3 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Brightest cluster galaxy #Coma (optics) #Coma Cluster #Galaxies: Formation, Evolution, Phenomena #Galaxy #Photometry (optics) #Population #Stellar population #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1111/j.1365-2966.2008.14080.x
11 pages, 8 figures. Accepted for publication in MNRAS. This replacement has mainly cosmetic textual changes but the model in figure 6 has been modified
arxiv created 2008/10/15 · openalex publication_date 2008/12/31 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We use 16 μm, Spitzer-Infrared Spectrograph, blue peak-up photometry of 50 early-type galaxies in the Coma cluster to define the mid-infrared colour–magnitude relation. We compare with recent simple stellar population models that include the mid-infrared emission from the extended, dusty envelopes of evolved stars. The Ks-[16] colour in these models is very sensitive to the relative population of dusty asymptotic giant branch stars. We find that the passively evolving early-type galaxies define a sequence of approximately constant age (∼10 Gyr) with varying metallicity. Several galaxies that lie on the optical/near-infrared colour–magnitude relation do not lie on the mid-infrared relation. This illustrates the sensitivity of the Ks-[16] colour to age. The fact that a colour–magnitude relation is seen in the mid-infrared underlines the extremely passive nature of the majority (68 per cent) of early-type galaxies in the Coma cluster. The corollary of this is that 32 per cent of the early-type galaxies in our sample are not‘passive’, insofar as they are either significantly younger than 10 Gyr or they have had some rejuvenation episode within the last few Gyr.