The first ISO workshop on analytical spectroscopy with SWS, LWS, PHT-S and CAM-CVF

(Oct 6-8, 1997, Madrid, Spain)

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LWS observations of a Statistical Sample of Late-Type Galaxies from the VIRGO Cluster

K. J. Leech 1 - H.J. Völk 2 - I. Heinrichsen 1 - H. Hippelein 3 - L. Metcalfe 1 - D. Pierini 2 - C. Popescu 2 - R.J. Tuffs 2 - C. Xu 4

1 ESA Villafranca, P.O. Box 50727, Madrid, Spain -
2 Max-Planck-Institut für Kernphysik, Heidelberg -
3 Max-Planck-Institut für Astronomie, Heidelberg -
4 IPAC, Caltech, USA

The ISO Guaranteed Time program VIRGO is an ISOPHOT 40 - 220 micron study of a complete volume-limited, unbiased sample of spiral, irregular and dwarf galaxies from the VIRGO cluster. From these galaxies a sample of 18 cluster spiral galaxies with integrated blue magnitudes Bt < 12.6 was selected for study with LWS around the [C II] 158 micron fine structure line. These 18 galaxies come from both the cluster core (within 2 degrees of M87) and periphery (more than 4 degrees from the position of maximum galaxy surface density).

Here we present a preliminary reduction and analysis of the LWS spectra. We have detected [C II] in 14 of the 18 galaxies. When detected it correlates approximately with the IRAS 60 and 100 $\mu$m fluxes. The instrumental setup used was insufficient to detect any background [C II] emission from our own galaxy. The data reduction was carried out using the ISO Spectral Analysis Package (ISAP) to process the LWS AAR data from the standard pipeline.

The [C II] cooling line probes not only photodissociation regions associated with massive star formation, but also the quiescent diffuse HI component of the interstellar medium. Future work will combine the [C II] line fluxes and the FIR continuum fluxes with optical, radio (synchrotron), UV and X-ray measurements to provide detailed information on the structure and energy balance of the ISM in disks of galaxies, as well as their current and past star-formation activity.

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Postscript version