SEGUE-2: Old Milky Way Stars Near and Far

Constance M. Rockosi, Young Sun Lee, Heather L. Morrison, Brian Yanny, Jennifer A. Johnson, Sara Lucatello, Jennifer Sobeck, Timothy C. Beers, Carlos Allende Prieto, Deokkeun An, Dmitry Bizyaev, Michael R. Blanton, Luca Casagrande, Daniel J. Eisenstein, Andrew Gould, James E. Gunn, Paul Harding, Inese I. Ivans, H. R. Jacobson, William JaneshGillian R. Knapp, Juna A. Kollmeier, Sébastien Lépine, Martín López-Corredoira, Zhibo Ma, Heidi J. Newberg, Kaike Pan, Jakub Prchlik, Conor Sayers, Katharine J. Schlesinger, Jennifer Simmerer, David H. Weinberg

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


The Sloan Extension for Galactic Understanding and Exploration 2 (SEGUE-2) obtained 128,288 low-resolution spectra (R ∼1800) of 118,958 unique stars in the first year of the Sloan Digital Sky Survey III (2008-2009). SEGUE-2 targeted prioritized distant halo tracers (blue horizontal-branch stars, K giants, and M giants) and metal-poor or kinematically hot populations. The main goal of SEGUE-2 was to target stars in the distant halo and measure their kinematics and chemical abundances to learn about the formation and evolution of the Milky Way. We present the SEGUE-2 field placement and target selection strategies. We discuss the success rate of the targeting based on the SEGUE-2 spectra and other spectroscopic and astrometric surveys. We describe the final SEGUE-2/SDSS-III improvements to the stellar parameter determinations based on the SEGUE Stellar Parameter Pipeline. We report a (g - i) color-effective temperature relation calibrated to the IRFM. We evaluate the accuracy and uncertainties associated with these stellar parameters by comparing with fundamental parameters, a sample of high-resolution spectra of SEGUE stars analyzed homogeneously, stars in well-studied clusters, and stars observed in common by the APOGEE survey. The final SEGUE spectra, calibration data, and derived parameters described here were released in SDSS-III Data Release 9 and continue to be included in all subsequent SDSS Data Releases. Because of its faint limiting magnitude and emphasis on the distant halo, the public SEGUE-2 data remain an important resource for the spectroscopy of stars in the Milky Way.

Original languageEnglish
Article number60
JournalAstrophysical Journal, Supplement Series
Issue number2
StatePublished - 1 Apr 2022

Bibliographical note

Funding Information:
C.M.R. acknowledges support from the David and Lucille Packard Foundation. H.L.M. thanks the National Science Foundation for support for this work under grant AST-1009886. H.L.M., C.M.R., and P.H. thank the NSF for support with grant AST-121989. P.H. thanks the NSF for their support under grant AST-1211144. The work was also supported in part by the National Science Foundation under grant No. PHYS-1066293 and the hospitality of the Aspen Center for Physics. L.C. is the recipient of ARC Future Fellowship FT160100402. D.A. acknowledges support from the NRF of Korea (NRF-2021R1A2C1004117). T.C.B. and Y.S.L. acknowledge partial support from grant PHY 14-30152; Physics Frontier Center/JINA Center for the Evolution of the Elements (JINA-CEE), awarded by the US National Science Foundation. Y.S.L. acknowledges support from the National Research Foundation (NRF) of Korea grant funded by the Ministry of Science and ICT (NRF-2018R1A2B6003961 and NRF-2021R1A2C1008679). We thank the Hobby–Eberly Telescope TAC for an important early allocation of time for the calibration data.

Funding Information:
Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the US Department of Energy Office of Science. The SDSS-III website is .

Publisher Copyright:
© 2022. The American Astronomical Society. All rights reserved.


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