Speaker
Description
Cold interstellar clouds are a necessary step on the way to star formation. Yet, understanding how these clouds form out of the warm diffuse medium, and what fundamental processes regulate their atomic and molecular fractions, has been largely unexplored. We have recently completed the first statistical study of the properties of neutral gas over the entire temperature range $10-10^4\,{\rm K}$. This project, "21 cm Spectral Line Observations of Neutral Gas with the (E)VLA" (21-SPONGE), is a large (58 lines of sight) survey of Galactic HI absorption with the Karl G. Jansky Very Large Array. Our exceptional sensitivity allows us to constrain the fraction of thermally unstable HI and place constraints on the importance of interstellar turbulence in the process of cold cloud formation. I will summarize key results from 21-SPONGE and also highlight several ongoing and future HI absorption studies that focus on mapping the CNM in the vicinity of molecular clouds using the VLA, and expanding the HI absorption samples using the Australian SKA Pathfinder array.
| Wish list question? | 10. What do theoretical models predict about the origin and fate of HI in and around galaxies? |
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