SEGUE-2: Old Milky Way Stars Near and Far

April 2022 • 2022ApJS..259...60R

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

Abstract • 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.


IPAC Authors

Jennifer Sobek

Associate Scientist