Speaker
Description
Cold hydrogen gas is the raw fuel for star formation in galaxies, and its partition into atomic and molecular phases is a key quantity for galaxy evolution. Observationally, it is still unclear whether at higher redshift atomic gas still plays an important role in the cold gas budget of galaxies, though the most common assumption is that HI becomes negligible already at $z \sim 0.3$.
In this talk, we will present results from the HIGHz survey, i.e., the largest representative sample of star-forming galaxies with HI information at $z \sim 0.2$. In particular, we combine ALMA and Arecibo data to estimate the molecular-to-atomic hydrogen mass ratio for some of the most massive gas-rich systems currently known. We show that the balance between atomic and molecular hydrogen in these galaxies is similar to that of local main-sequence disks, implying that atomic hydrogen has been dominating the cold gas mass budget of star-forming galaxies for at least the past three billion years. In addition, despite harboring gas reservoirs that are more typical of objects at the cosmic noon, HIGHz galaxies host regular rotating disks with low gas velocity dispersions suggesting that high total gas fractions do not necessarily drive high turbulence in the interstellar medium.
| Wish list question? | 1. Just how well do we know the cosmic evolution of Omega_HI(z) and Omega_H2(z)? |
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