A Lasting Legacy into the SKA Era

VLASS stands on the shoulders of the pioneering NVSS and FIRST surveys carried out with the VLA from 1993 to 2011. VLASS additionally sets the stage for future radio surveys and facilities, such as surveys using the SKA Precursors MeerKAT and ASKAP, leading to Phase 1 science operations of the SKA that will commence in the late 2020s. Both of these facilities include dedicated surveys at ≈1.4 GHz as a prime component of their science programs. The observing band and parameters of VLASS, and the fact that VLASS surveys 65% of the Southern sky, means that it will be complementary to these lower frequency programs. From the point of view of the dynamic radio sky, VLASS will also provide a unique snapshot of the universe some 20 yr after the NVSS and FIRST surveys.

Much of the science of VLASS depends on identification of radio sources in the optical/infrared. Fortunately, many innovative surveys in these wavebands are planned for the next decade. In the optical, both the Zwicky Transient Facility and the Vera Rubin Observatory will provide access to information on optical transients, and the Rubin Observatory will also produce a deep, multiband galaxy survey over the whole southern sky. With a planned launch date in 2022, the Euclid mission will survey 15,000 square degrees of sky, mostly within the area covered by VLASS, in the optical and near-infrared, resulting in subarcsecond resolution imaging and grism spectroscopy of a large fraction of the host galaxies of VLASS sources. Spectroscopic surveys with the next generation of fiber spectrographs will obtain many millions of galaxy spectra, including the hosts of VLASS sources. These can be used not only for redshifts and classifications, but also for studying the stellar populations and metal contents of the host galaxies. By 2030, we expect ≈50% of VLASS sources to have reliable photometric redshifts from a combination of space-based infrared and ground-based optical photometry, and ≈20% to have spectroscopic redshifts from large spectroscopic surveys.

For further details of the science case and survey design of VLASS, see the VLASS Description Paper.

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