In collaboration with Suzanne Madden (Saclay, France) and her research team, I used the Infrared Space Observatory to obtain far-infrared spectroscopic measurements of irregular galaxies and low luminosity Virgo spirals. These galaxies have low proportions of heavy elements in their interstellar medium compared to more massive galaxies such as the Milky Way.

For comparison with these data, we used the 12 meter telescope on Kitt Peak in Arizona to measure the 2.6 millimeter line of carbon monoxide in some of these galaxies.

Some initial results on 5 spiral galaxies in the Virgo Cluster are presented below (from B. J. Smith and S. C. Madden, 1997, Astronomical Journal, 114, 138). Notice that the relative CO and [C II] line strengths differ from galaxy to galaxy. In particular, notice that NGC 4294 and NGC 4299 have strong [C II] emission but weak CO emission, indicating they have more molecular gas than previously thought. The optical images are from the Digitalized Palomar Observatory Sky Survey and are 3.1 arcminutes in diameter.

Galaxy	Optical Image	2.6mm CO Spectrum	158 micron [C II] Spectrum
NGC 4189
NGC 4222
NGC 4294
NGC 4299
NGC 4522

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