SEGUE-2: Old Milky Way Stars Near and Far Rockosi, Constance M.; Sun Lee, Young; Morrison, Heather L. ...
The Astrophysical journal. Supplement series,
04/2022, Letnik:
259, Številka:
2
Journal Article
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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.
We determine the extinction law through Cep OB3b, a young cluster of 3000 stars undergoing gas dispersal. The extinction is measured toward 76 background K giants identified with MMT/Hectospec ...spectra. Color excess ratios were determined toward each of the giants using V and R photometry from the literature, g, r, i, and z photometry from the Sloan Digital Sky Survey and J, H, and K sub(s) photometry from the Two Micron All Sky Survey. These color excess ratios were then used to construct the extinction law through the dusty material associated with Cep OB3b. The extinction law through Cep OB3b is intermediate between the R sub(V) = 3.1 and R sub(V) = 5 laws commonly used for the diffuse atomic interstellar medium and dense molecular clouds, respectively. The dependence of the extinction law on line-of-sight A sub(V) is investigated and we find the extinction law becomes shallower for regions with A sub(V) > 2.5 mag. We speculate that the intermediate dust law results from dust processing during the dispersal of the molecular cloud by the cluster.
We determine the extinction law through Cep OB3b, a young cluster of 3000 stars undergoing gas dispersal. The extinction is measured toward 76 background K giants identified with MMT/Hectospec ...spectra. Color excess ratios were determined toward each of the giants using \(V\) and \(R\) photometry from the literature, \(g\),\(r\),\(i\) and \(z\) photometry from SDSS and \(J\), \(H\), and \(K_{s}\) photometry from 2MASS. These color excess ratios were the used to construct the extinction law through the dusty material associated with Cep OB3b. The extinction law through Cep OB3b is intermediate between the \(R_{V} = 3.1\) and \(R_{V} = 5\) laws commonly used for the diffuse atomic ISM and dense molecular clouds, respectively. The dependence of the extinction law on line-of-sight \(A_{V}\) is investigated and we find the extinction law becomes shallower for regions with \(A_{V} > 2.5\) magnitudes. We speculate that the intermediate dust law results from dust processing during the dispersal of the molecular cloud by the cluster.
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