  We present Herschel, ALMA, and MUSE observations of the molecular ring of
Messier 104, also known as the Sombrero galaxy. These previously unpublished
archival data shed new light on the content of the interstellar medium of M104.
In particular, molecular hydrogen measured by CO emission and dust measured by
far-infrared light are uniformly distributed along the ring. The ionized gas
revealed by H$\alpha$ and [CII] emission is distributed in knots along the
ring. Despite being classified as an SAa galaxy, M104 displays features typical
of early-type galaxies. We therefore compared its [CII] and dust emission to a
sample of early-type galaxies observed with Herschel and SOFIA. The [CII]/FIR
ratio of M104 is much lower than that of typical star-forming galaxies and is
instead much more similar to that of early-type galaxies. By classifying
regions using optical emission line diagnostics we also find that regions
classified as HII lie closer to star-forming galaxies in the [CII]/FIR diagram
than those classified as low-ionization emission regions. The good match
between [CII] and H$\alpha$ emission in conjunction with the lack of
correlation between CO emission and star formation suggest that there is very
limited active star formation along the ring and that most of the [CII]
emission is from ionized and neutral atomic gas rather than molecular gas. From
the total intensity of the CO line we estimate a molecular hydrogen mass of
0.9$\times10^9$M$_{\odot}$, a value intermediate between those of early type
galaxies and the content of the molecular ring of our galaxy.
