Gas flows into and out of galaxies are an important component of galaxy
formation and evolution. A key element is the multiphase circum-galactic
medium, through which in- and outflows are passing, and its connection to the
baryons in the host galaxies. Detections of the diffuse gas phase in the
outskirts of galaxies is to date mostly achieved through quasar absorption
line studies. However, the link to the physical properties of the absorber
host galaxies is still debated and studies of their molecular gas phase from
which the stars form are still in their infancy.
From dedicated observing projects as well as using the largest (sub)mm survey,
ALMACAL, we have detected CO emission from the host galaxies of known
intervening absorbers. The detection of absorber host galaxies in multiple CO
transitions offer first insights in the ISM conditions of these galaxies
indicating higher excitation than in normal star-forming
galaxies. Furthermore, combining the (sub)mm observations with optical IFU
studies using MUSE reveals a more complex picture of absorption-selected
systems.