Speaker
Description
In the era of SKA it will finally be possible to detect HI in emission beyond $z \sim 0$ over medium and wide area surveys. This will allow us to constrain the redshift evolution of HI emission in much finer detail than what is currently possible with stacking experiments and pencil beam surveys. With this improved data we will be much better equipped to address the apparent disconnect that exists between the abundance of HI in emission and its inferred abundance traced by Ly$\alpha$ absorption at higher redshift.
I will present the HI galaxy mass function (HIMF) estimated from the final ALFALFA HI source catalogue, which represents one of the most precise measurements of $\Omega_\mathrm{HI}$ at $z \sim 0$, based on well over 20,000 galaxies detected in HI. However, a thorough exploration of potential sources of uncertainty reveals that there is still a ~10-20% uncertainty in this value driven primarily by cosmic variance and the absolute calibration of flux. In addition to these points, ALFALFA has also demonstrated that source confusion is likely to present a significant challenge for the deepest stacking experiments in precursor surveys, and that measurements of $\Omega_\mathrm{HI}$ and the HIMF in $z$ bins will require the inclusion of priors on the relationship between HI mass and rotation velocity. I will discuss these points in the context of future HI galaxy surveys with SKA precursors, pathfinders, and the advent of SKA1.
| 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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