Overview of the DESI Milky Way Survey
Andrew P. Cooper, S. E. Koposov, Carlos Allende Prieto, Christopher J. Manser, Namitha Kizhuprakkat, Adam D. Myers, Arjun Dey, B. T. Gänsicke, Ting S. Li, Constance M. Rockosi, Monica Valluri, Joan Najita, Alis J. Deason, Anand Raichoor, M. S. Wang, Yuan-Sen Ting, Bokyoung Kim, Andreia Carrillo, Wenting Wang, Leandro Beraldo e Silva, J. Han, Jiani Ding, M. Sánchez‐Conde, J. Aguilar, S. P. Ahlen, S. Bailey, Vasily Belokurov, D. Brooks, Kátia Cunha, Kyle Dawson, Axel de la Macorra, P. Doel, Daniel J. Eisenstein, Parker Fagrelius, Kevin Fanning, Andreu Font-Ribera, J. E. Forero-Romero, E. Gaztañaga, Satya Gontcho A Gontcho, J. Guy, K. Honscheid, R. Kehoe, Theodore Kisner, Anthony Kremin, Martin Landriau, M. E. Levi, Paul Martini, Aaron Meisner, R. Miquel, John Moustakas, Jundan Nie, N. Palanque‐Delabrouille, Will J. Percival, Claire Poppett, Francisco Prada, Nabeel Rehemtulla, Edward F. Schlafly, David J. Schlegel, M. Schubnell, R. M. Sharples, G. Tarlé, Risa H. Wechsler, David H. Weinberg, Zhimin Zhou, Hu Zou
Abstract
Abstract We describe the Milky Way Survey (MWS) that will be undertaken with the Dark Energy Spectroscopic Instrument (DESI) on the Mayall 4 m telescope at the Kitt Peak National Observatory. Over the next 5 yr DESI MWS will observe approximately seven million stars at Galactic latitudes ∣ b ∣ > 20°, with an inclusive target selection scheme focused on the thick disk and stellar halo. MWS will also include several high-completeness samples of rare stellar types, including white dwarfs, low-mass stars within 100 pc of the Sun, and horizontal branch stars. We summarize the potential of DESI to advance understanding of the Galactic structure and stellar evolution. We introduce the final definitions of the main MWS target classes and estimate the number of stars in each class that will be observed. We describe our pipelines for deriving radial velocities, atmospheric parameters, and chemical abundances. We use ≃500,000 spectra of unique stellar targets from the DESI Survey Validation program (SV) to demonstrate that our pipelines can measure radial velocities to ≃1 km s −1 and [Fe/H] accurate to ≃0.2 dex for typical stars in our main sample. We find the stellar parameter distributions from ≈100 deg 2 of SV observations with ≳90% completeness on our main sample are in good agreement with expectations from mock catalogs and previous surveys.