Speaker
Description
The HI mass function is a crucial tool to understand the evolution of the HI content in galaxies over cosmic times, and hence, to constrain both the baryon cycle in galaxy evolution and the reionization history of the Universe. However, the intrinsic faintness of the 21cm line has made it hitherto prohibitive to measure it directly from HI galaxy surveys beyond the nearby Universe. In this talk, I present recently-derived semi-empirical constraints on the HI mass function and the $\Omega_{\rm HI}$ parameter at $z\sim 0.37$. Specifically, we leverage the combination of literature results on the stellar mass function from optical surveys with recent findings on the $M_{\rm HI}-M_\star$ scaling relation derived via spectral stacking analysis applied to 21-cm line interferometric data from the MIGHTEE and CHILES surveys, conducted with the MeerKAT and VLA radio telescopes, respectively. We find evolution of the HIMF at $z\sim 0.37$ with respect to results at $z\sim 0$ from the ALFALFA survey and at $z\sim 1$ from uGMRT data. Our results for $\Omega_{\rm HI}$ are in broad agreement with other literature results, and follow the overall trend on $\Omega_{\rm HI}$ as a function of redshift, deviating at $\sim 2.9\sigma$ from the ALFALFA result at $z\sim 0$. Our findings therefore hint towards an evolution of the HIMF and of the cosmic HI density over the last 8 billion years, supporting a picture of smooth transition of the HI content of star-forming galaxies from $z\sim 0$ to $z\sim 1$.
| Topics | Galaxy Evolution & AGN |
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