Speaker
Description
Hydrogen is the fuel for star formation, but relatively little is known about the role of cold gas in galaxy evolution. The COSMOS HI Large Extragalactic Survey (CHILES) is an on-going deep (1000 hr) HI survey being carried out with the Karl G. Jansky Very Large Array (VLA), probing a 0.5 degree region within the COSMOS field in the 21 cm line of neutral hydrogen. CHILES is the first survey to observe the HI 21 cm line in emission from $z = 0$ to $z \sim 0.5$, allowing us to observe the content, morphology and kinematics of the neutral hydrogen in relation to stellar disks, and how it may have evolved over this period. Here, we will present the results of a simulation of the galaxy detections possible with this survey, with an emphasis on the high-mass galaxies which should be detectable in the first 178 hours of the survey (epoch I). This will be compared with predictions of galaxy detections using artificial sources of similar scale inside of existing CHILES image cubes.
The results of our galaxy detections will be used to calculate and refine the high-mass end of the HI mass function (HIMF). The HIMF describes the intrinsic distribution of galaxies as a function of their HI mass. Because cosmological simulations make use of gas content and environmental factors, studying variations in the HIMF due to changes in redshift and environment can constrain the current models of galaxy formation. The HIMF has been well-studied in the local universe (e.g. Zwaan et al. 2005, Jones et al. 2018), and a Schechter function has been found to fit the data well. This function uses a power law to describe the low-mass slope and an exponential decline for the high-mass end. With the full 1000-hr CHILES data, we will be able to detect galaxies with HI masses of $10^{10}\,M_\odot$ out to a redshift of $z=0.11$, and we will be able to detect galaxies with HI masses of $3 \times 10^{10}\,M_\odot$ at the highest redshift of the survey, $z=0.5$, and use these to calculate the high-mass end of the HIMF as a function of redshift and environment, as well as to obtain the first measurements of cosmic HI density ($\Omega_{\rm HI}$) derived from individual HI emission measurements at $z=0.5$.
| 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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