Mid-IR emission of galaxies in the Virgo cluster III. The data^*

¹ Laboratoire d'Astrophysique de Marseille, BP 8, Traverse du Siphon, 13376 Marseille Cedex 12, France e-mail: Alessandro.Boselli@oamp.fr
² DSM/DAPNIA/Service d'Astrophysique, CEA/Saclay, 91191 Gif-sur-Yvette, France e-mail: msauvage@cea.fr
³ DEMIRM and URA 336 du CNRS, Observatoire de Paris, 61 Av. de l'Observatoire, 75014 Paris, France e-mail: James.Lequeux@obspm.fr
⁴ Università degli Studi di Milano-Bicocca, Dipartimento di Fisica, Piazza dell'Ateneo Nuovo 1, 20126 Milano, Italy e-mail: Alessandro.Donati@mib.infn.it;Giuseppe.Gavazzi@mib.infn.it

Corresponding author: A. Boselli, Alessandro.Boselli@oamp.fr

Received: 1 October 2002
Accepted: 16 May 2003

Abstract

We present ISOCAM imaging data at 6.75 and 15 μm for 145 galaxies in the Virgo cluster and in the Coma/A1367 supercluster. Of these, 99 form a complete, optically-selected, volume-limited sample including galaxies in the core and in the periphery of the Virgo cluster, suitable for statistical analysis. 34 of the Virgo galaxies were resolved by ISOCAM: for these objects we present mid-IR images, radial light and colour profiles, as well as effective and isophotal radii, surface brightness and light concentration indices. The mid-IR colours of the target galaxies show a weak trend with the H band luminosity, with values of F(6.75 μm)/F(15 μm) ≥ 1 found generally in massive objects ( ), and F(6.75 μm)/F(15 μm) ≤ 1 in low-mass (L_H ≤ 10¹⁰ ) dwarf galaxies. All early-type galaxies (type ≤ S0a) have F(6.75 μm)/F(15 μm) ≥ 1, as expected when the mid-IR emission is dominated by the photosphere of the cold stellar population. The mid-IR, near-IR and visible light concentration indices of bright galaxies are tightly correlated with one another, indicating that the spatial distribution of the mid-IR emitting sources is, to the first order, similar to that of the stars.