The Experts below are selected from a list of 11367 Experts worldwide ranked by ideXlab platform
Carlos Allende Prieto - One of the best experts on this subject based on the ideXlab platform.
-
Apogee data releases 13 and 14 stellar parameter and abundance comparisons with independent analyses
The Astronomical Journal, 2018Co-Authors: Carlos Allende Prieto, Henrik Jonsson, Jon A Holtzman, D Feuillet, Keith Hawkins, Katia CunhaAbstract:Data from the SDSS-IV/Apache Point Observatory Galactic Evolution Experiment (Apogee-2) have been released as part of SDSS Data Releases 13 (DR13) and 14 (DR14). These include high-resolution H-band spectra, radial velocities, and derived stellar parameters and abundances. DR13, released in 2016 August, contained Apogee data for roughly 150,000 stars, and DR14, released in 2017 August, added about 110,000 more. Stellar parameters and abundances have been derived with an automated pipeline, the Apogee Stellar Parameter and Chemical Abundance Pipeline (ASPCAP). We evaluate the performance of this pipeline by comparing the derived stellar parameters and abundances to those inferred from optical spectra and analysis for several hundred stars. For most elements-C, Na, Mg, Al, Si, S, Ca, Cr, Mn, Ni-the DR14 ASPCAP analyses have systematic differences with the comparisons samples of less than 0.05 dex (median), and random differences of less than 0.15 dex (standard deviation). These differences are a combination of the uncertainties in both the comparison samples as well as the ASPCAP analysis. Compared to the references, magnesium is the most accurate alpha-element derived by ASPCAP, and shows a very clear thin/thick disk separation, while nickel is the most accurate iron-peak element (besides iron itself). (Less)
-
Apogee data releases 13 and 14 stellar parameter and abundance comparisons with independent analyses
arXiv: Solar and Stellar Astrophysics, 2018Co-Authors: Carlos Allende Prieto, Henrik Jonsson, Jon A Holtzman, D Feuillet, Keith Hawkins, Katia CunhaAbstract:Data from the SDSS-IV / Apache Point Observatory Galactic Evolution Experiment (Apogee-2) have been released as part of SDSS Data Releases 13 (DR13) and 14 (DR14). These include high resolution H-band spectra, radial velocities, and derived stellar parameters and abundances. DR13, released in August 2016, contained Apogee data for roughly 150,000 stars, and DR14, released in August 2017, added about 110,000 more. Stellar parameters and abundances have been derived with an automated pipeline, the Apogee Stellar Parameter and Chemical Abundance Pipeline (ASPCAP). We evaluate the performance of this pipeline by comparing the derived stellar parameters and abundances to those inferred from optical spectra and analysis for several hundred stars. For most elements -- C, Na, Mg, Al, Si, S, Ca, Cr, Mn, Ni -- the DR14 ASPCAP analysis have systematic differences with the comparisons samples of less than 0.05 dex (median), and random differences of less than 0.15 dex (standard deviation). These differences are a combination of the uncertainties in both the comparison samples as well as the ASPCAP-analysis. Compared to the references, magnesium is the most accurate alpha-element derived by ASPCAP, and shows a very clear thin/thick disk separation, while nickel is the most accurate iron-peak element (besides iron).
-
the data reduction pipeline for the apache point observatory galactic evolution experiment
The Astronomical Journal, 2015Co-Authors: Carlos Allende Prieto, David L Nidever, Dmitry Bizyaev, Jon A Holtzman, Stephane Beland, Chad F Bender, Adam BurtonAbstract:The Apache Point Observatory Galactic Evolution Experiment (Apogee), part of the Sloan Digital Sky Survey III, explores the stellar populations of the Milky Way using the Sloan 2.5-m telescope linked to a high resolution (R ~ 22,500), near-infrared (1.51–1.70 µm) spectrograph with 300 optical fibers. For over 150,000 predominantly red giant branch stars that Apogee targeted across the Galactic bulge, disks and halo, the collected high signal-to-noise ratio (>100 per half-resolution element) spectra provide accurate (~0.1 km s-1) RVs, stellar atmospheric parameters, and precise (lesssim0.1 dex) chemical abundances for about 15 chemical species. Here we describe the basic Apogee data reduction software that reduces multiple 3D raw data cubes into calibrated, well-sampled, combined 1D spectra, as implemented for the SDSS-III/Apogee data releases (DR10, DR11 and DR12). The processing of the near-IR spectral data of Apogee presents some challenges for reduction, including automated sky subtraction and telluric correction over a 3°-diameter field and the combination of spectrally dithered spectra. We also discuss areas for future improvement.
-
abundances stellar parameters and spectra from the sdss iii Apogee survey
The Astronomical Journal, 2015Co-Authors: Jon A Holtzman, Carlos Allende Prieto, Dmitry Bizyaev, Brett H. Andrews, Jennifer A Johnson, Timothy C. Beers, Matthew Shetrone, F Anders, Michael R BlantonAbstract:The SDSS-III/Apache Point Observatory Galactic Evolution Experiment (Apogee) survey operated from 2011–2014 using the Apogee spectrograph, which collects high-resolution (R ~ 22,500), near-IR (1.51–1.70 µm) spectra with a multiplexing (300 fiber-fed objects) capability. We describe the survey data products that are publicly available, which include catalogs with radial velocity, stellar parameters, and 15 elemental abundances for over 150,000 stars, as well as the more than 500,000 spectra from which these quantities are derived. Calibration relations for the stellar parameters (Teff , log g, [M/H], [a/M]) and abundances (C, N, O, Na, Mg, Al, Si, S, K, Ca, Ti, V, Mn, Fe, Ni) are presented and discussed. The internal scatter of the abundances within clusters indicates that abundance precision is generally between 0.05 and 0.09 dex across a broad temperature range; it is smaller for some elemental abundances within more limited ranges and at high signal-to-noise ratio. We assess the accuracy of the abundances using comparison of mean cluster metallicities with literature values, Apogee observations of the solar spectrum and of Arcturus, comparison of individual star abundances with other measurements, and consideration of the locus of derived parameters and abundances of the entire sample, and find that it is challenging to determine the absolute abundance scale; external accuracy may be good to 0.1–0.2 dex. Uncertainties may be larger at cooler temperatures (Teff < 4000 K). Access to the public data release and data products is described, and some guidance for using the data products is provided.
-
the apache point observatory galactic evolution experiment Apogee
arXiv: Instrumentation and Methods for Astrophysics, 2015Co-Authors: Steven R Majewski, Adam Burton, Basil Blank, Carlos Allende Prieto, Ricardo P Schiavon, Peter M Frinchaboy, Dmitry Bizyaev, Robert H Barkhouser, Sophia Brunner, R CarreraAbstract:The Apache Point Observatory Galactic Evolution Experiment (Apogee), one of the programs in the Sloan Digital Sky Survey III (SDSS-III), has now completed its systematic, homogeneous spectroscopic survey sampling all major populations of the Milky Way. After a three year observing campaign on the Sloan 2.5-m Telescope, Apogee has collected a half million high resolution (R~22,500), high S/N (>100), infrared (1.51-1.70 microns) spectra for 146,000 stars, with time series information via repeat visits to most of these stars. This paper describes the motivations for the survey and its overall design---hardware, field placement, target selection, operations---and gives an overview of these aspects as well as the data reduction, analysis and products. An index is also given to the complement of technical papers that describe various critical survey components in detail. Finally, we discuss the achieved survey performance and illustrate the variety of potential uses of the data products by way of a number of science demonstrations, which span from time series analysis of stellar spectral variations and radial velocity variations from stellar companions, to spatial maps of kinematics, metallicity and abundance patterns across the Galaxy and as a function of age, to new views of the interstellar medium, the chemistry of star clusters, and the discovery of rare stellar species. As part of SDSS-III Data Release 12, all of the Apogee data products are now publicly available.
Jon A Holtzman - One of the best experts on this subject based on the ideXlab platform.
-
the similarity of abundance ratio trends and nucleosynthetic patterns in the milky way disk and bulge
arXiv: Solar and Stellar Astrophysics, 2020Co-Authors: Emily Griffith, Rachael L Beaton, Henrik Jonsson, Jon A Holtzman, David H Weinberg, Jennifer A Johnson, D A Garciahernandez, Sten Hasselquist, J Johnson, Richard R LaneAbstract:We compare abundance ratio trends in a sample of $\sim 11,000$ Milky Way bulge stars ($R_{\rm GC} < 3$ kpc) from the Apache Point Observatory Galactic Evolution Experiment (Apogee) to those of Apogee stars in the Galactic disk ($5$ kpc $< R_{\rm GC} < 11$ kpc). We divide each sample into low-Ia (high-[Mg/Fe]) and high-Ia (low-[Mg/Fe]) populations, and in each population we examine the median trends of [X/Mg] vs. [Mg/H] for elements X = Fe, O, Na, Al, Si, P, S, K, Ca, V, Cr, Mn, Co, Ni, Cu, and Ce. To remove small systematic trends of Apogee abundances with stellar $\log(g)$, we resample the disk stars to match the $\log(g)$ distributions of the bulge data. After doing so, we find nearly identical median trends for low-Ia disk and bulge stars for all elements. High-Ia trends are similar for most elements, with noticeable (0.05-0.1 dex) differences for Mn, Na, and Co. The close agreement of abundance trends (with typical differences $\lesssim 0.03$ dex) implies that similar nucleosynthetic processes enriched bulge and disk stars despite the different star formation histories and physical conditions of these regions. For example, we infer that differences in the high mass slope of the stellar initial mass function (IMF) between disk and bulge must have been $\lesssim 0.30$. This agreement, and the generally small scatter about the median sequences, means that one can predict all of a bulge star's Apogee abundances with good accuracy knowing only its measured [Mg/Fe] and [Mg/H] and the observed trends of disk stars.
-
Apogee data releases 13 and 14 stellar parameter and abundance comparisons with independent analyses
The Astronomical Journal, 2018Co-Authors: Carlos Allende Prieto, Henrik Jonsson, Jon A Holtzman, D Feuillet, Keith Hawkins, Katia CunhaAbstract:Data from the SDSS-IV/Apache Point Observatory Galactic Evolution Experiment (Apogee-2) have been released as part of SDSS Data Releases 13 (DR13) and 14 (DR14). These include high-resolution H-band spectra, radial velocities, and derived stellar parameters and abundances. DR13, released in 2016 August, contained Apogee data for roughly 150,000 stars, and DR14, released in 2017 August, added about 110,000 more. Stellar parameters and abundances have been derived with an automated pipeline, the Apogee Stellar Parameter and Chemical Abundance Pipeline (ASPCAP). We evaluate the performance of this pipeline by comparing the derived stellar parameters and abundances to those inferred from optical spectra and analysis for several hundred stars. For most elements-C, Na, Mg, Al, Si, S, Ca, Cr, Mn, Ni-the DR14 ASPCAP analyses have systematic differences with the comparisons samples of less than 0.05 dex (median), and random differences of less than 0.15 dex (standard deviation). These differences are a combination of the uncertainties in both the comparison samples as well as the ASPCAP analysis. Compared to the references, magnesium is the most accurate alpha-element derived by ASPCAP, and shows a very clear thin/thick disk separation, while nickel is the most accurate iron-peak element (besides iron itself). (Less)
-
Apogee data releases 13 and 14 stellar parameter and abundance comparisons with independent analyses
arXiv: Solar and Stellar Astrophysics, 2018Co-Authors: Carlos Allende Prieto, Henrik Jonsson, Jon A Holtzman, D Feuillet, Keith Hawkins, Katia CunhaAbstract:Data from the SDSS-IV / Apache Point Observatory Galactic Evolution Experiment (Apogee-2) have been released as part of SDSS Data Releases 13 (DR13) and 14 (DR14). These include high resolution H-band spectra, radial velocities, and derived stellar parameters and abundances. DR13, released in August 2016, contained Apogee data for roughly 150,000 stars, and DR14, released in August 2017, added about 110,000 more. Stellar parameters and abundances have been derived with an automated pipeline, the Apogee Stellar Parameter and Chemical Abundance Pipeline (ASPCAP). We evaluate the performance of this pipeline by comparing the derived stellar parameters and abundances to those inferred from optical spectra and analysis for several hundred stars. For most elements -- C, Na, Mg, Al, Si, S, Ca, Cr, Mn, Ni -- the DR14 ASPCAP analysis have systematic differences with the comparisons samples of less than 0.05 dex (median), and random differences of less than 0.15 dex (standard deviation). These differences are a combination of the uncertainties in both the comparison samples as well as the ASPCAP-analysis. Compared to the references, magnesium is the most accurate alpha-element derived by ASPCAP, and shows a very clear thin/thick disk separation, while nickel is the most accurate iron-peak element (besides iron).
-
baade s window and Apogee metallicities ages and chemical abundances
Astronomy and Astrophysics, 2017Co-Authors: MARKUS SCHULTHEIS, A Rojasarriagada, A Garcia E Perez, Govind Nandakumar, K Cunha, Allende C Prieto, Henrik Jonsson, Michael R. Hayden, Jon A HoltzmanAbstract:Context. Baade's window (BW) is one of the most observed Galactic bulge fields in terms of chemical abundances. Owing to its low and homogeneous interstellar absorption it is considered the perfect calibration field for Galactic bulge studies. Aims. In the era of large spectroscopic surveys, calibration fields such as BW are necessary for cross calibrating the stellar parameters and individual abundances of the Apogee survey. Methods. We use the Apogee BW stars to derive the metallicity distribution function (MDF) and individual abundances for α-and iron-peak elements of the Apogee ASPCAP pipeline (DR13), as well as the age distribution for stars in BW. Results. We determine the MDF of Apogee stars in BW and find a remarkable agreement with that of the Gaia-ESO survey (GES). Both exhibit a clear bimodal distribution. We also find that the Mg-metallicity planes of the two surveys agree well, except for the metal-rich part ([Fe/H] > 0.1), where Apogee finds systematically higher Mg abundances with respect to the GES. The ages based on the [C/N] ratio reveal a bimodal age distribution, with a major old population at ~ 10 Gyr, with a decreasing tail towards younger stars. A comparison of stellar parameters determined by Apogee and those determined by other sources reveals detectable systematic offsets, in particular for spectroscopic surface gravity estimates. In general, we find a good agreement between individual abundances of O, Na, Mg, Al, Si, K, Ca, Cr, Mn, Co, and Ni from Apogee with that of literature values. Conclusions. We have shown that in general Apogee data show a good agreement in terms of MDF and individual chemical abundances with respect to literature works. Using the [C/N] ratio we found a significant fraction of young stars in BW. (Less)
-
baade s window and Apogee metallicities ages and chemical abundances
Astronomy and Astrophysics, 2017Co-Authors: MARKUS SCHULTHEIS, A Rojasarriagada, A Garcia E Perez, Govind Nandakumar, K Cunha, Allende C Prieto, Henrik Jonsson, Michael R. Hayden, Jon A HoltzmanAbstract:Context. Baade's window (BW) is one of the most observed Galactic bulge fields in terms of chemical abundances. Owing to its low and homogeneous interstellar absorption it is considered the perfect calibration field for Galactic bulge studies. Aims. In the era of large spectroscopic surveys, calibration fields such as BW are necessary for cross calibrating the stellar parameters and individual abundances of the Apogee survey. Methods. We use the Apogee BW stars to derive the metallicity distribution function (MDF) and individual abundances for α-and iron-peak elements of the Apogee ASPCAP pipeline (DR13), as well as the age distribution for stars in BW. Results. We determine the MDF of Apogee stars in BW and find a remarkable agreement with that of the Gaia-ESO survey (GES). Both exhibit a clear bimodal distribution. We also find that the Mg-metallicity planes of the two surveys agree well, except for the metal-rich part ([Fe/H] > 0.1), where Apogee finds systematically higher Mg abundances with respect to the GES. The ages based on the [C/N] ratio reveal a bimodal age distribution, with a major old population at ~ 10 Gyr, with a decreasing tail towards younger stars. A comparison of stellar parameters determined by Apogee and those determined by other sources reveals detectable systematic offsets, in particular for spectroscopic surface gravity estimates. In general, we find a good agreement between individual abundances of O, Na, Mg, Al, Si, K, Ca, Cr, Mn, Co, and Ni from Apogee with that of literature values. Conclusions. We have shown that in general Apogee data show a good agreement in terms of MDF and individual chemical abundances with respect to literature works. Using the [C/N] ratio we found a significant fraction of young stars in BW. (Less)
Dmitry Bizyaev - One of the best experts on this subject based on the ideXlab platform.
-
the sdss iii Apogee spectral line list for h band spectroscopy
Astrophysical Journal Supplement Series, 2015Co-Authors: Matthew D Shetrone, Katia Cunha, Verne V. Smith, Allende C Prieto, Dmitry Bizyaev, Jon A Holtzman, Jennifer A Johnson, J E Lawler, Ana G PerezAbstract:We present the H-band spectral line lists adopted by the Apache Point Observatory Galactic Evolution Experiment (Apogee). The Apogee line lists comprise astrophysical, theoretical, and laboratory sources from the literature, as well as newly evaluated astrophysical oscillator strengths and damping parameters. We discuss the construction of the Apogee line list, which is one of the critical inputs for the Apogee Stellar Parameters and Chemical Abundances Pipeline, and present three different versions that have been used at various stages of the project. The methodology for the newly calculated astrophysical line lists is reviewed. The largest of these three line lists contains 134,457 molecular and atomic transitions. In addition to the format adopted to store the data, the line lists are available in MOOG, Synspec, and Turbospectrum formats. The limitations of the line lists along with guidance for its use on different spectral types are discussed. We also present a list of H-band spectral features that are either poorly represented or completely missing in our line list. This list is based on the average of a large number of spectral fit residuals for Apogee observations spanning a wide range of stellar parameters.
-
the data reduction pipeline for the apache point observatory galactic evolution experiment
The Astronomical Journal, 2015Co-Authors: Carlos Allende Prieto, David L Nidever, Dmitry Bizyaev, Jon A Holtzman, Stephane Beland, Chad F Bender, Adam BurtonAbstract:The Apache Point Observatory Galactic Evolution Experiment (Apogee), part of the Sloan Digital Sky Survey III, explores the stellar populations of the Milky Way using the Sloan 2.5-m telescope linked to a high resolution (R ~ 22,500), near-infrared (1.51–1.70 µm) spectrograph with 300 optical fibers. For over 150,000 predominantly red giant branch stars that Apogee targeted across the Galactic bulge, disks and halo, the collected high signal-to-noise ratio (>100 per half-resolution element) spectra provide accurate (~0.1 km s-1) RVs, stellar atmospheric parameters, and precise (lesssim0.1 dex) chemical abundances for about 15 chemical species. Here we describe the basic Apogee data reduction software that reduces multiple 3D raw data cubes into calibrated, well-sampled, combined 1D spectra, as implemented for the SDSS-III/Apogee data releases (DR10, DR11 and DR12). The processing of the near-IR spectral data of Apogee presents some challenges for reduction, including automated sky subtraction and telluric correction over a 3°-diameter field and the combination of spectrally dithered spectra. We also discuss areas for future improvement.
-
abundances stellar parameters and spectra from the sdss iii Apogee survey
The Astronomical Journal, 2015Co-Authors: Jon A Holtzman, Carlos Allende Prieto, Dmitry Bizyaev, Brett H. Andrews, Jennifer A Johnson, Timothy C. Beers, Matthew Shetrone, F Anders, Michael R BlantonAbstract:The SDSS-III/Apache Point Observatory Galactic Evolution Experiment (Apogee) survey operated from 2011–2014 using the Apogee spectrograph, which collects high-resolution (R ~ 22,500), near-IR (1.51–1.70 µm) spectra with a multiplexing (300 fiber-fed objects) capability. We describe the survey data products that are publicly available, which include catalogs with radial velocity, stellar parameters, and 15 elemental abundances for over 150,000 stars, as well as the more than 500,000 spectra from which these quantities are derived. Calibration relations for the stellar parameters (Teff , log g, [M/H], [a/M]) and abundances (C, N, O, Na, Mg, Al, Si, S, K, Ca, Ti, V, Mn, Fe, Ni) are presented and discussed. The internal scatter of the abundances within clusters indicates that abundance precision is generally between 0.05 and 0.09 dex across a broad temperature range; it is smaller for some elemental abundances within more limited ranges and at high signal-to-noise ratio. We assess the accuracy of the abundances using comparison of mean cluster metallicities with literature values, Apogee observations of the solar spectrum and of Arcturus, comparison of individual star abundances with other measurements, and consideration of the locus of derived parameters and abundances of the entire sample, and find that it is challenging to determine the absolute abundance scale; external accuracy may be good to 0.1–0.2 dex. Uncertainties may be larger at cooler temperatures (Teff < 4000 K). Access to the public data release and data products is described, and some guidance for using the data products is provided.
-
the apache point observatory galactic evolution experiment Apogee
arXiv: Instrumentation and Methods for Astrophysics, 2015Co-Authors: Steven R Majewski, Adam Burton, Basil Blank, Carlos Allende Prieto, Ricardo P Schiavon, Peter M Frinchaboy, Dmitry Bizyaev, Robert H Barkhouser, Sophia Brunner, R CarreraAbstract:The Apache Point Observatory Galactic Evolution Experiment (Apogee), one of the programs in the Sloan Digital Sky Survey III (SDSS-III), has now completed its systematic, homogeneous spectroscopic survey sampling all major populations of the Milky Way. After a three year observing campaign on the Sloan 2.5-m Telescope, Apogee has collected a half million high resolution (R~22,500), high S/N (>100), infrared (1.51-1.70 microns) spectra for 146,000 stars, with time series information via repeat visits to most of these stars. This paper describes the motivations for the survey and its overall design---hardware, field placement, target selection, operations---and gives an overview of these aspects as well as the data reduction, analysis and products. An index is also given to the complement of technical papers that describe various critical survey components in detail. Finally, we discuss the achieved survey performance and illustrate the variety of potential uses of the data products by way of a number of science demonstrations, which span from time series analysis of stellar spectral variations and radial velocity variations from stellar companions, to spatial maps of kinematics, metallicity and abundance patterns across the Galaxy and as a function of age, to new views of the interstellar medium, the chemistry of star clusters, and the discovery of rare stellar species. As part of SDSS-III Data Release 12, all of the Apogee data products are now publicly available.
-
the sdss iii Apogee spectral line list for h band spectroscopy
arXiv: Instrumentation and Methods for Astrophysics, 2015Co-Authors: Matthew D Shetrone, Katia Cunha, Verne V. Smith, Carlos Allende Prieto, Dmitry Bizyaev, Jon A Holtzman, Jennifer A Johnson, J E Lawler, Ana G Perez, Szabolcs MeszarosAbstract:We present the $H$-band spectral line lists adopted by the Apache Point Observatory Galactic Evolution Experiment (Apogee). The Apogee line lists comprise astrophysical, theoretical, and laboratory sources from the literature, as well as newly evaluated astrophysical oscillator strengths and damping parameters. We discuss the construction of the Apogee line list, which is one of the critical inputs for the Apogee Stellar Parameters and Chemical Abundances Pipeline, and present three different versions that have been used at various stages of the project. The methodology for the newly calculated astrophysical line lists is reviewed. The largest of these three line lists contains 134,457 molecular and atomic transitions. In addition to the format adopted to store the data, the line lists are available in MOOG, Synspec and Turbospectrum formats. We also present a list of $H$-band spectral features that are either poorly represented or completely missing in our line list. This list is based on the average of a large number of spectral fit residuals for Apogee observations spanning a wide range of stellar parameters.
David L Nidever - One of the best experts on this subject based on the ideXlab platform.
-
the data reduction pipeline for the apache point observatory galactic evolution experiment
The Astronomical Journal, 2015Co-Authors: Carlos Allende Prieto, David L Nidever, Dmitry Bizyaev, Jon A Holtzman, Stephane Beland, Chad F Bender, Adam BurtonAbstract:The Apache Point Observatory Galactic Evolution Experiment (Apogee), part of the Sloan Digital Sky Survey III, explores the stellar populations of the Milky Way using the Sloan 2.5-m telescope linked to a high resolution (R ~ 22,500), near-infrared (1.51–1.70 µm) spectrograph with 300 optical fibers. For over 150,000 predominantly red giant branch stars that Apogee targeted across the Galactic bulge, disks and halo, the collected high signal-to-noise ratio (>100 per half-resolution element) spectra provide accurate (~0.1 km s-1) RVs, stellar atmospheric parameters, and precise (lesssim0.1 dex) chemical abundances for about 15 chemical species. Here we describe the basic Apogee data reduction software that reduces multiple 3D raw data cubes into calibrated, well-sampled, combined 1D spectra, as implemented for the SDSS-III/Apogee data releases (DR10, DR11 and DR12). The processing of the near-IR spectral data of Apogee presents some challenges for reduction, including automated sky subtraction and telluric correction over a 3°-diameter field and the combination of spectrally dithered spectra. We also discuss areas for future improvement.
-
the data reduction pipeline for the apache point observatory galactic evolution experiment
arXiv: Instrumentation and Methods for Astrophysics, 2015Co-Authors: Carlos Allende Prieto, David L Nidever, Dmitry Bizyaev, Jon A Holtzman, Stephane Beland, Chad F Bender, Adam BurtonAbstract:The Apache Point Observatory Galactic Evolution Experiment (Apogee), part of the Sloan Digital Sky Survey III, explores the stellar populations of the Milky Way using the Sloan 2.5-m telescope linked to a high resolution (R~22,500), near-infrared (1.51-1.70 microns) spectrograph with 300 optical fibers. For over 150,000 predominantly red giant branch stars that Apogee targeted across the Galactic bulge, disks and halo, the collected high S/N (>100 per half-resolution element) spectra provide accurate (~0.1 km/s) radial velocities, stellar atmospheric parameters, and precise (~0.1 dex) chemical abundances for about 15 chemical species. Here we describe the basic Apogee data reduction software that reduces multiple 3D raw data cubes into calibrated, well-sampled, combined 1D spectra, as implemented for the SDSS-III/Apogee data releases (DR10, DR11 and DR12). The processing of the near-IR spectral data of Apogee presents some challenges for reduction, including automated sky subtraction and telluric correction over a 3 degree diameter field and the combination of spectrally dithered spectra. We also discuss areas for future improvement.
-
the Apogee red clump catalog precise distances velocities and high resolution elemental abundances over a large area of the milky way s disk
The Astrophysical Journal, 2014Co-Authors: Jo Bovy, Drew S Chojnowski, Peter M Frinchaboy, David L Nidever, Jon A Holtzman, Hans-walter Rix, Gail Zasowski, Leo Girardi, Courtney R Epstein, Michael R. HaydenAbstract:The Sloan Digital Sky Survey III's Apache Point Observatory Galactic Evolution Experiment (Apogee) is a high-resolution near-infrared spectroscopic survey covering all of the major components of the Galaxy, including the dust-obscured regions of the inner Milky Way disk and bulge. Here we present a sample of 10,341 likely red-clump stars (RC) from the first two years of Apogee operations, selected based on their position in color-metallicity-surface-gravity-effective-temperature space using a new method calibrated using stellar evolution models and high-quality asteroseismology data. The narrowness of the RC locus in color-metallicity-luminosity space allows us to assign distances to the stars with an accuracy of 5%-10%. The sample extends to typical distances of about 3 kpc from the Sun, with some stars out to 8 kpc, and spans a volume of approximately 100 kpc{sup 3} over 5 kpc ≲ R ≲ 14 kpc, |Z| ≲ 2 kpc, and –15° ≲ Galactocentric azimuth ≲ 30°. The Apogee red-clump (Apogee-RC) catalog contains photometry from the Two Micron All Sky Survey, reddening estimates, distances, line-of-sight velocities, stellar parameters and elemental abundances determined from the high-resolution Apogee spectra, and matches to major proper motion catalogs. We determine the survey selection function for this data set and discuss howmore » the RC selection samples the underlying stellar populations. We use this sample to limit any azimuthal variations in the median metallicity within the ≈45° azimuthal region covered by the current sample to be ≤0.02 dex, which is more than an order of magnitude smaller than the radial metallicity gradient. This result constrains coherent non-axisymmetric flows within a few kiloparsecs from the Sun.« less
-
the Apogee red clump catalog precise distances velocities and high resolution elemental abundances over a large area of the milky way s disk
arXiv: Astrophysics of Galaxies, 2014Co-Authors: Jo Bovy, Drew S Chojnowski, Peter M Frinchaboy, David L Nidever, Jon A Holtzman, Hans-walter Rix, Gail Zasowski, Leo Girardi, Courtney R Epstein, Michael R. HaydenAbstract:The Sloan Digital Sky Survey III's Apache Point Observatory Galactic Evolution Experiment (Apogee) is a high-resolution near-infrared spectroscopic survey covering all of the major components of the Galaxy, including the dust-obscured regions of the inner Milky Way disk and bulge. Here we present a sample of 10,341 likely red-clump stars (RC) from the first two years of Apogee operations, selected based on their position in color-metallicity-surface-gravity-effective-temperature space using a new method calibrated using stellar-evolution models and high-quality asteroseismology data. The narrowness of the RC locus in color-metallicity-luminosity space allows us to assign distances to the stars with an accuracy of 5 to 10%. The sample extends to typical distances of about 3 kpc from the Sun, with some stars out to 8 kpc, and spans a volume of approximately 100 kpc^3 over 5 kpc <~ R <~ 14 kpc, |Z| <~ 2 kpc, and -15 deg <~ Galactocentric azimuth <~ 30 deg. The Apogee red-clump (Apogee-RC) catalog contains photometry from 2MASS, reddening estimates, distances, line-of-sight velocities, stellar parameters and elemental abundances determined from the high-resolution Apogee spectra, and matches to major proper motion catalogs. We determine the survey selection function for this data set and discuss how the RC selection samples the underlying stellar populations. We use this sample to limit any azimuthal variations in the median metallicity within the ~45 degree-wide azimuthal region covered by the current sample to be <= 0.02 dex, which is more than an order of magnitude smaller than the radial metallicity gradient. This result constrains coherent non-axisymmetric flows within a few kpc from the Sun.
-
development of fiber fabry perot interferometers as stable near infrared calibration sources for high resolution spectrographs
Publications of the Astronomical Society of the Pacific, 2014Co-Authors: Samuel Halverson, Frederick R Hearty, David L Nidever, Suvrath Mahadevan, Lawrence W Ramsey, J Wilson, Jon Holtzman, Stephen L Redman, Gillian Nave, Matthew J NelsonAbstract:We discuss the ongoing development of single-mode fiber Fabry-Perot (FFP) Interferometers as precise astrophotonic calibration sources for high precision radial velocity (RV) spectrographs. FFPs are simple, inexpensive, monolithic units that can yield a stable and repeatable output spectrum. An FFP is a unique alternative to a traditional etalon, as the interferometric cavity is made of single-mode fiber rather than an air-gap spacer. This design allows for excellent collimation, high spectral finesse, rigid mechanical stability, insensitivity to vibrations, and no need for vacuum operation. The device we have tested is a commercially available product from Micron Optics.10 Our development path is targeted toward a calibration source for the Habitable-Zone Planet Finder (HPF), a near-infrared spectrograph designed to detect terrestrial-mass planets around low-mass stars, but this reference could also be used in many existing and planned fiber-fed spectrographs as we illustrate using the Apache Point Observatory Galactic Evolution Experiment (Apogee) instrument. With precise temperature control of the fiber etalon, we achieve a thermal stability of 100 μK and associated velocity uncertainty of 22 cm s-1. We achieve a precision of ≈2 m s-1 in a single Apogee fiber over 12 hr using this new photonic reference after removal of systematic correlations. This high precision (close to the expected photon-limited floor) is a testament to both the excellent intrinsic wavelength stability of the fiber interferometer and the stability of the Apogee instrument design. Overall instrument velocity precision is 80 cm s-1 over 12 hr when averaged over all 300 Apogee fibers and after removal of known trends and pressure correlations, implying the fiber etalon is intrinsically stable to significantly higher precision.
Katia Cunha - One of the best experts on this subject based on the ideXlab platform.
-
Apogee data releases 13 and 14 stellar parameter and abundance comparisons with independent analyses
The Astronomical Journal, 2018Co-Authors: Carlos Allende Prieto, Henrik Jonsson, Jon A Holtzman, D Feuillet, Keith Hawkins, Katia CunhaAbstract:Data from the SDSS-IV/Apache Point Observatory Galactic Evolution Experiment (Apogee-2) have been released as part of SDSS Data Releases 13 (DR13) and 14 (DR14). These include high-resolution H-band spectra, radial velocities, and derived stellar parameters and abundances. DR13, released in 2016 August, contained Apogee data for roughly 150,000 stars, and DR14, released in 2017 August, added about 110,000 more. Stellar parameters and abundances have been derived with an automated pipeline, the Apogee Stellar Parameter and Chemical Abundance Pipeline (ASPCAP). We evaluate the performance of this pipeline by comparing the derived stellar parameters and abundances to those inferred from optical spectra and analysis for several hundred stars. For most elements-C, Na, Mg, Al, Si, S, Ca, Cr, Mn, Ni-the DR14 ASPCAP analyses have systematic differences with the comparisons samples of less than 0.05 dex (median), and random differences of less than 0.15 dex (standard deviation). These differences are a combination of the uncertainties in both the comparison samples as well as the ASPCAP analysis. Compared to the references, magnesium is the most accurate alpha-element derived by ASPCAP, and shows a very clear thin/thick disk separation, while nickel is the most accurate iron-peak element (besides iron itself). (Less)
-
Apogee data releases 13 and 14 stellar parameter and abundance comparisons with independent analyses
arXiv: Solar and Stellar Astrophysics, 2018Co-Authors: Carlos Allende Prieto, Henrik Jonsson, Jon A Holtzman, D Feuillet, Keith Hawkins, Katia CunhaAbstract:Data from the SDSS-IV / Apache Point Observatory Galactic Evolution Experiment (Apogee-2) have been released as part of SDSS Data Releases 13 (DR13) and 14 (DR14). These include high resolution H-band spectra, radial velocities, and derived stellar parameters and abundances. DR13, released in August 2016, contained Apogee data for roughly 150,000 stars, and DR14, released in August 2017, added about 110,000 more. Stellar parameters and abundances have been derived with an automated pipeline, the Apogee Stellar Parameter and Chemical Abundance Pipeline (ASPCAP). We evaluate the performance of this pipeline by comparing the derived stellar parameters and abundances to those inferred from optical spectra and analysis for several hundred stars. For most elements -- C, Na, Mg, Al, Si, S, Ca, Cr, Mn, Ni -- the DR14 ASPCAP analysis have systematic differences with the comparisons samples of less than 0.05 dex (median), and random differences of less than 0.15 dex (standard deviation). These differences are a combination of the uncertainties in both the comparison samples as well as the ASPCAP-analysis. Compared to the references, magnesium is the most accurate alpha-element derived by ASPCAP, and shows a very clear thin/thick disk separation, while nickel is the most accurate iron-peak element (besides iron).
-
elemental abundances of kepler objects of interest in Apogee i two distinct orbital period regimes inferred from host star iron abundances
arXiv: Earth and Planetary Astrophysics, 2017Co-Authors: Robert F Wilson, Katia Cunha, Verne V. Smith, Steven R Majewski, Diogo Souto, Chad F Bender, Suvrath Mahadevan, Johanna Teske, Nicholas TroupAbstract:The Apache Point Observatory Galactic Evolution Experiment (Apogee) has observed $\sim$600 transiting exoplanets and exoplanet candidates from \textit{Kepler} (Kepler Objects of Interest, KOIs), most with $\geq$18 epochs. The combined multi-epoch spectra are of high signal-to-noise (typically $\geq$100) and yield precise stellar parameters and chemical abundances. We first confirm the ability of the Apogee abundance pipeline, ASPCAP, to derive reliable [Fe/H] and effective temperatures for FGK dwarf stars -- the primary \textit{Kepler} host stellar type -- by comparing the ASPCAP-derived stellar parameters to those from independent high-resolution spectroscopic characterizations for 221 dwarf stars in the literature. With a sample of 282 close-in ($P<100$ days) KOIs observed in the Apogee KOI goal program, we find a correlation between orbital period and host star [Fe/H] characterized by a critical period, $P_\mathrm{crit}$= $8.3^{+0.1}_{-4.1}$ days, below which small exoplanets orbit statistically more metal-enriched host stars. This effect may trace a metallicity dependence of the protoplanetary disk inner-radius at the time of planet formation or may be a result of rocky planet ingestion driven by inward planetary migration. We also consider that this may trace a metallicity dependence of the dust sublimation radius, but find no statistically significant correlation with host $T_\mathrm{eff}$ and orbital period to support such a claim.
-
the sdss iii Apogee spectral line list for h band spectroscopy
Astrophysical Journal Supplement Series, 2015Co-Authors: Matthew D Shetrone, Katia Cunha, Verne V. Smith, Allende C Prieto, Dmitry Bizyaev, Jon A Holtzman, Jennifer A Johnson, J E Lawler, Ana G PerezAbstract:We present the H-band spectral line lists adopted by the Apache Point Observatory Galactic Evolution Experiment (Apogee). The Apogee line lists comprise astrophysical, theoretical, and laboratory sources from the literature, as well as newly evaluated astrophysical oscillator strengths and damping parameters. We discuss the construction of the Apogee line list, which is one of the critical inputs for the Apogee Stellar Parameters and Chemical Abundances Pipeline, and present three different versions that have been used at various stages of the project. The methodology for the newly calculated astrophysical line lists is reviewed. The largest of these three line lists contains 134,457 molecular and atomic transitions. In addition to the format adopted to store the data, the line lists are available in MOOG, Synspec, and Turbospectrum formats. The limitations of the line lists along with guidance for its use on different spectral types are discussed. We also present a list of H-band spectral features that are either poorly represented or completely missing in our line list. This list is based on the average of a large number of spectral fit residuals for Apogee observations spanning a wide range of stellar parameters.
-
the sdss iii Apogee spectral line list for h band spectroscopy
arXiv: Instrumentation and Methods for Astrophysics, 2015Co-Authors: Matthew D Shetrone, Katia Cunha, Verne V. Smith, Carlos Allende Prieto, Dmitry Bizyaev, Jon A Holtzman, Jennifer A Johnson, J E Lawler, Ana G Perez, Szabolcs MeszarosAbstract:We present the $H$-band spectral line lists adopted by the Apache Point Observatory Galactic Evolution Experiment (Apogee). The Apogee line lists comprise astrophysical, theoretical, and laboratory sources from the literature, as well as newly evaluated astrophysical oscillator strengths and damping parameters. We discuss the construction of the Apogee line list, which is one of the critical inputs for the Apogee Stellar Parameters and Chemical Abundances Pipeline, and present three different versions that have been used at various stages of the project. The methodology for the newly calculated astrophysical line lists is reviewed. The largest of these three line lists contains 134,457 molecular and atomic transitions. In addition to the format adopted to store the data, the line lists are available in MOOG, Synspec and Turbospectrum formats. We also present a list of $H$-band spectral features that are either poorly represented or completely missing in our line list. This list is based on the average of a large number of spectral fit residuals for Apogee observations spanning a wide range of stellar parameters.