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Southern Spectroscopic Roadmap

The Cosmic Visions Dark Energy group was established in 2015 to collect community input and identify priorities to extend cosmology surveys beyond the currently planned experiments. We have identified optical/IR spectroscopy as an area with significant potential for dedicated facilities at the scale of LSST, especially if such a facility can survey the southern sky. With current technologies and telescope designs, such a survey could begin at a scale of the DESI instrument outfitted on a 10-m class telescope. Observations coordinated with LSST would greatly reduce the uncertainties associated with photometric redshifts, enable the measurements of spectroscopic redshifts of tens of thousands of supernovae and other transients, provide accurate velocity dispersions for galaxy clusters, and offer spectroscopic insight into many other sources measured photometrically by LSST. If the telescope is designed to allow a larger instrument and possible wide-field adaptive optics, this facility could be upgraded to lead to the ultimate spectroscopic survey around the conclusion of LSST’s current program. A facility covering the IR to optical with 50,000-100,000 fibers would be capable of producing a galaxy sample of hundreds of millions of spectra. A facility of this scale will also enable spectroscopy of hundreds of millions of stars. A dedicated survey of this scale will allow measurements of galaxy clustering to non-linear scales for redshifts z<1.5, measurements of all linear modes to z=3.5, and offer insight into astrophysics at all scales. A roadmap that progressively scales spectroscopic capabilities will need to address several challenges, from telescope availability, to new instrumentation work, to theory. (This abstract is based in part on and discussions at earlier meetings.)

Proposed by Kyle Dawson on behalf of Cosmic Visions Dark Energy Panel (University of Utah)