Browsing by Subject "resolution infrared-spectroscopy"

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Calibrations Of Atmospheric Parameters Obtained From The First Year Of Sdss-III APOGEE Observations
(2013-11) Meszaros, S.; Holtzman, J.; Perez, A. E. Garcia; Prieto, C. Allende; Schiavon, R. P.; Basu, S.; Bizyaev, D.; Chaplin, W. J.; Chojnowski, S. D.; Cunha, K.; Elsworth, Y.; Epstein, C.; Frinchaboy, P. M.; Garcia, R. A.; Hearty, F. R.; Hekker, S.; Johnson, J. A.; Kallinger, T.; Koesterke, L.; Majewski, S. R.; Martell, S. L.; Nidever, D.; Pinsonneault, M. H.; O'Connell, J.; Shetrone, M.; Smith, V. V.; Wilson, J. C.; Zasowski, G.; Koesterke, L.
The Sloan Digital Sky Survey III (SDSS-III) Apache Point Observatory Galactic Evolution Experiment (APOGEE) is a three-year survey that is collecting 105 high-resolution spectra in the near-IR across multiple Galactic populations. To derive stellar parameters and chemical compositions from this massive data set, the APOGEE Stellar Parameters and Chemical Abundances Pipeline (ASPCAP) has been developed. Here, we describe empirical calibrations of stellar parameters presented in the first SDSS-III APOGEE data release (DR10). These calibrations were enabled by observations of 559 stars in 20 globular and open clusters. The cluster observations were supplemented by observations of stars in NASA's Kepler field that have well determined surface gravities from asteroseismic analysis. We discuss the accuracy and precision of the derived stellar parameters, considering especially effective temperature, surface gravity, and metallicity; we also briefly discuss the derived results for the abundances of the a-elements, carbon, and nitrogen. Overall, we find that ASPCAP achieves reasonably accurate results for temperature and metallicity, but suffers from systematic errors in surface gravity. We derive calibration relations that bring the raw ASPCAP results into better agreement with independently determined stellar parameters. The internal scatter of ASPCAP parameters within clusters suggests that metallicities are measured with a precision better than 0.1 dex, effective temperatures better than 150 K, and surface gravities better than 0.2 dex. The understanding provided by the clusters and Kepler giants on the current accuracy and precision will be invaluable for future improvements of the pipeline.
Sodium and Oxygen Abundances in the Open Cluster NGC 6791 from APOGEE H-Band Spectroscopy
(2015-01) Cunha, Katia; Smith, Verne V.; Johnson, Jennifer A.; Bergemann, Maria; Meszaros, Szabolcs; Shetrone, Matthew D.; Souto, Diogo; Allende Prieto, Carlos; Schiavon, Ricardo P.; Frinchaboy, Peter; Zasowski, Gail; Bizyaev, Dmitry; Holtzman, Jon; Perez, Ana E. Garcia; Majewski, Steven R.; Nidever, David; Beers, Timothy; Carrera, Ricardo; Geisler, Doug; Gunn, James; Hearty, Fred; Ivans, Inese; Martell, Sarah; Pinsonneault, Marc; Schneider, Donald P.; Sobeck, Jennifer; Stello, Dennis; Stassun, Keivan G.; Shetrone, Matthew D.
The open cluster NGC 6791 is among the oldest, most massive, and metal-rich open clusters in the Galaxy. High-resolution H-band spectra from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) of 11 red giants in NGC 6791 are analyzed for their chemical abundances of iron, oxygen, and sodium. The abundances of these three elements are found to be homogeneous (with abundance dispersions at the level of similar to 0.05-0.07 dex) in these cluster red giants, which span much of the red-giant branch (T-eff similar to 3500-4600 K), and include two red clump giants. From the infrared spectra, this cluster is confirmed to be among the most metal-rich clusters in the Galaxy (<[Fe/H]> = 0.34 +/- 0.06) and is found to have a roughly solar value of [O/Fe] and slightly enhanced [Na/Fe]. Our non-LTE calculations for the studied Na I lines in the APOGEE spectral region (16373.86 angstrom and 16388.85 angstrom) indicate only small departures from LTE (<= 0.04 dex) for the parameter range and metallicity of the studied stars. The previously reported double population of cluster members with different Na abundances is not found among the studied sample.
Target Selection For The Apache Point Observatory Galactic Evolution Experiment (APOGEE)
(2013-10) Zasowski, G.; Johnson, J. A.; Frinchaboy, P. M.; Majewski, S. R.; Nidever, D. L.; Pinto, H. J. R.; Girardi, L.; Andrews, B.; Chojnowski, S. D.; Cudworth, K. M.; Jackson, K.; Munn, J.; Skrutskie, M. F.; Beaton, R. L.; Blake, C. H.; Covey, K.; Deshpande, R.; Epstein, C.; Fabbian, D.; Fleming, S. W.; Hernandez, D. A. G.; Herrero, A.; Mahadevan, S.; Meszaros, S.; Schultheis, M.; Sellgren, K.; Terrien, R.; van Saders, J.; Prieto, C. A.; Bizyaev, D.; Burton, A.; Cunha, K.; da Costa, L. N.; Hasselquist, S.; Hearty, F.; Holtzman, J.; Perez, A. E. G.; Maia, M. A. G.; O'Connell, R. W.; O'Donnell, C.; Pinsonneault, M.; Santiago, B. X.; Schiavon, R. P.; Shetrone, M.; Smith, V.; Wilson, J. C.; Frinchaboy, P. M.; Jackson, K.
The Apache Point Observatory Galactic Evolution Experiment (APOGEE) is a high-resolution infrared spectroscopic survey spanning all Galactic environments (i.e., bulge, disk, and halo), with the principal goal of constraining dynamical and chemical evolution models of the Milky Way. APOGEE takes advantage of the reduced effects of extinction at infrared wavelengths to observe the inner Galaxy and bulge at an unprecedented level of detail. The survey's broad spatial and wavelength coverage enables users of APOGEE data to address numerous Galactic structure and stellar populations issues. In this paper we describe the APOGEE targeting scheme and document its various target classes to provide the necessary background and reference information to analyze samples of APOGEE data with awareness of the imposed selection criteria and resulting sample properties. APOGEE's primary sample consists of similar to 10(5) red giant stars, selected to minimize observational biases in age and metallicity. We present the methodology and considerations that drive the selection of this sample and evaluate the accuracy, efficiency, and caveats of the selection and sampling algorithms. We also describe additional target classes that contribute to the APOGEE sample, including numerous ancillary science programs, and we outline the targeting data that will be included in the public data releases.
Target Selection For The Apache Point Observatory Galactic Evolution Experiment (APOGEE)
(2013-10) Zasowski, G.; Johnson, J. A.; Frinchaboy, P. M.; Majewski, S. R.; Nidever, D. L.; Pinto, H. J. R.; Girardi, L.; Andrews, B.; Chojnowski, S. D.; Cudworth, K. M.; Jackson, K.; Munn, J.; Skrutskie, M. F.; Beaton, R. L.; Blake, C. H.; Covey, K.; Deshpande, R.; Epstein, C.; Fabbian, D.; Fleming, S. W.; Hernandez, D. A. G.; Herrero, A.; Mahadevan, S.; Meszaros, S.; Schultheis, M.; Sellgren, K.; Terrien, R.; van Saders, J.; Prieto, C. A.; Bizyaev, D.; Burton, A.; Cunha, K.; da Costa, L. N.; Hasselquist, S.; Hearty, F.; Holtzman, J.; Perez, A. E. G.; Maia, M. A. G.; O'Connell, R. W.; O'Donnell, C.; Pinsonneault, M.; Santiago, B. X.; Schiavon, R. P.; Shetrone, M.; Smith, V.; Wilson, J. C.; Frinchaboy, P. M.; Jackson, K.
The Apache Point Observatory Galactic Evolution Experiment (APOGEE) is a high-resolution infrared spectroscopic survey spanning all Galactic environments (i.e., bulge, disk, and halo), with the principal goal of constraining dynamical and chemical evolution models of the Milky Way. APOGEE takes advantage of the reduced effects of extinction at infrared wavelengths to observe the inner Galaxy and bulge at an unprecedented level of detail. The survey's broad spatial and wavelength coverage enables users of APOGEE data to address numerous Galactic structure and stellar populations issues. In this paper we describe the APOGEE targeting scheme and document its various target classes to provide the necessary background and reference information to analyze samples of APOGEE data with awareness of the imposed selection criteria and resulting sample properties. APOGEE's primary sample consists of similar to 10(5) red giant stars, selected to minimize observational biases in age and metallicity. We present the methodology and considerations that drive the selection of this sample and evaluate the accuracy, efficiency, and caveats of the selection and sampling algorithms. We also describe additional target classes that contribute to the APOGEE sample, including numerous ancillary science programs, and we outline the targeting data that will be included in the public data releases.