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

Abstract

We present ISOCAM imaging data at 6.75 and 15 mu m 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 mu m)/F(15 mu m) ge 1 found generally in massive objects (L_H>=10¹⁰ L_Hsun), and F(6.75 mu m)/F(15 mu m) le 1 in low-mass (L_H <= 10¹⁰ L_Hsun) dwarf galaxies. All early-type galaxies (type le S0a) have F(6.75 mu m)/F(15 mu m) ge 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.

Figures 1 and 2, and Tables 1, 2, 4, 5 are only available in electronic form at http://www.edpsciences.org