The ALMA Spectroscopic Survey in the HUDF: CO luminosity functions and the molecular gas content of galaxies through cosmic history

Understand

We use the results from the ALMA large program ASPECS, the spectroscopic survey in the Hubble Ultra Deep Field (HUDF), to constrain CO luminosity functions of galaxies and the resulting redshift evolution of $\rho$(H$_2$).

• The broad frequency range covered enables us to identify CO emission lines of different rotational transitions in the HUDF at $z>1$.
• We find strong evidence that the CO luminosity function evolves with redshift, with the knee of the CO luminosity function decreasing in luminosity by an order of magnitude from $\sim$2 to the local universe.
• Based on Schechter fits, we estimate that our observations recover the majority (up to $\sim$90%, depending on the assumptions on the faint end) of the total cosmic CO luminosity at $z$=1.0-3.1.