The High Latitude Spectroscopic Survey on the Nancy Grace Roman Space Telescope

March 2022 • 2022ApJ...928....1W

Authors • Wang, Yun • Zhai, Zhongxu • Alavi, Anahita • Massara, Elena • Pisani, Alice • Benson, Andrew • Hirata, Christopher M. • Samushia, Lado • Weinberg, David H. • Colbert, James • Doré, Olivier • Eifler, Tim • Heinrich, Chen • Ho, Shirley • Krause, Elisabeth • Padmanabhan, Nikhil • Spergel, David • Teplitz, Harry I.

Abstract • The Nancy Grace Roman Space Telescope will conduct a High Latitude Spectroscopic Survey (HLSS) over a large volume at high redshift, using the near-IR grism (1.0-1.93 μm, R = 435-865) and the 0.28 deg2 wide-field camera. We present a reference HLSS that maps 2000 deg2 and achieves an emission-line flux limit of 10-16 erg s-1 cm-2 at 6.5σ, requiring ~0.6 yr of observing time. We summarize the flowdown of the Roman science objectives to the science and technical requirements of the HLSS. We construct a mock redshift survey over the full HLSS volume by applying a semianalytic galaxy formation model to a cosmological N-body simulation and use this mock survey to create pixel-level simulations of 4 deg2 of HLSS grism spectroscopy. We find that the reference HLSS would measure ~10 million Hα galaxy redshifts that densely map large-scale structure at z = 1-2 and 2 million [O III] galaxy redshifts that sparsely map structures at z = 2-3. We forecast the performance of this survey for measurements of the cosmic expansion history with baryon acoustic oscillations and the growth of large-scale structure with redshift-space distortions. We also study possible deviations from the reference design and find that a deep HLSS at f line > 7 × 10-17 erg s-1 cm-2 over 4000 deg2 (requiring ~1.5 yr of observing time) provides the most compelling stand-alone constraints on dark energy from Roman alone. This provides a useful reference for future optimizations. The reference survey, simulated data sets, and forecasts presented here will inform community decisions on the final scope and design of the Roman HLSS.


IPAC Authors


Anahita Alavi

Assistant Scientist

James Colbert

Associate Scientist


Harry Teplitz

Senior Scientist


Yun Wang

Senior Scientist