EDP Sciences
Free access
Volume 402, Number 1, April IV 2003
Page(s) 37 - 51
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20030219

A&A 402, 37-51 (2003)
DOI: 10.1051/0004-6361:20030219

UV to radio centimetric spectral energy distributions of optically-selected late-type galaxies in the Virgo cluster

A. Boselli1, G. Gavazzi2 and G. Sanvito2

1  Laboratoire d'Astrophysique de Marseille, BP 8, Traverse du Siphon, 13376 Marseille Cedex 12, France
2  Università degli Studi di Milano-Bicocca, Dipartimento di Fisica, Piazza dell'Ateneo Nuovo 1, 20126 Milano, Italy
    e-mail: Giuseppe.Gavazzi@mib.infn.it; Gerry.Sanvito@mib.infn.it

(Received 10 October 2002 / Accepted 16 December 2002)

We present a multifrequency dataset for an optically-selected, volume-limited, complete sample of 118 late-type galaxies ( $\geq$S0a) in the Virgo cluster. The database includes UV, visible, near-IR, mid-IR, far-IR, radio continuum photometric data as well as spectroscopic data of H $\alpha$, CO and HI lines, homogeneously reduced, obtained from our own observations or compiled from the literature. Assuming the energy balance between the absorbed stellar light and that radiated in the IR by dust, we calibarte an empirical attenuation law suitable for correcting photometric and spectroscopic data of normal galaxies. The data, corrected for internal extinction, are used to construct the spectral energy distribution (SED) of each individual galaxy, and combined to trace the median SED of galaxies in various classes of morphological type and luminosity. Low-luminosity, dwarf galaxies have on average bluer stellar continua and higher far-IR luminosities per unit galaxy mass than giant, early-type spirals. If compared to nearby starburst galaxies such as M 82 and Arp 220, normal spirals have relatively similar observed stellar spectra but 10-100 times lower IR luminosities. The temperature of the cold dust component increases with the far-IR luminosity, from giant spirals to dwarf irregulars. The SED are used to separate the stellar emission from the dust emission in the mid-IR regime. We show that the contribution of the stellar emission at 6.75  $\mu$m to the total emission of galaxies is generally important, from ~80% in Sa to ~20% in Sc.

Key words: galaxies: general -- galaxies: spiral -- galaxies: ISM -- galaxies: stellar content

Offprint request: A. Boselli, Alessandro.Boselli@oamp.fr

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