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

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 (LH ≥ 1010 LH⊙), and F(6.75 μm)/F(15 μm) ≤ 1 in low-mass (LH ≤ 1010 LH⊙) 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.