The EVLA: Prospects for HI

To continue the unparalleled success of the Very Large Array (VLA) for radio astronomy, the facility is currently being converted to become the 'Expanded VLA' (EVLA). The EVLA will radically improve the VLA in order to cover the full 0.93–50 GHz radio wavelength range without gaps, provide up to an order of magnitude better sensitivity, and to allow observations at much larger bandwidths and spectral resolution as currently possible. For observations of the 21 cm line of atomic neutral hydrogen (HI), the EVLA offers thousands of km s^−1 velocity coverage at sub-km s^−1 resolution for targeted observations as well as an improved spectral baseline stability. In addition, every L-band (21 cm) continuum or targeted HI observation can be set-up to simultaneously observe a full z = 0−0.53 HI redshift survey at a velocity resolution of a few km s^−1. In turn, every HI observation will also yield deep radio continuum images of the field. These synergies will deliver a wealth of data which opens up a wide 'discovery space' to study the details of galaxy evolution and cosmology.