VLA-DISK : Connecting the extended disk of galaxies to their CGM

We mounted the first controlled experiment that will use UV QSO absorption-line spectra obtained with the Hubble Space Telescope (COS-DISK survey) in conjunction with HI 21cm line images from the VLA to probe the disk-halo interface. The VLA HI 21cm data will probe the structure, extent, and kinematics of the outer disks down to column densities of 10¹⁹ atoms cm^-2, while the UV spectra will probe HI columns of 10^20-14 atoms cm^-2 out to 3.5 times HI radius (~50-80kpc). The combination COS-DISK and VLA-DISk, together with data from the COS-GASS survey, will allow us to probe gas out to the virial radii of galaxies. We will compare our observations with state-of-the-art numerical simulations providing important constraints both on the physical prescriptions for gas cooling and stellar and black-hole feedback. We plan to generate mock data cubes of the HI and synthetic UV-absorption spectra of the disk-halo interface that will enable us to analyze the simulations in the same way as the observations.

The VLA-DISK program has 180 hours of VLA data in D- and C-configurations mapping 35 nearby galaxies.