Browse > Article
http://dx.doi.org/10.5303/JKAS.2022.55.2.23

ESTIMATION OF NITROGEN-TO-IRON ABUNDANCE RATIOS FROM LOW-RESOLUTION SPECTRA  

Kim, Changmin (Department of Astronomy, Space Science and Geology, Chungnam National University)
Lee, Young Sun (Department of Astronomy and Space Science, Chungnam National University)
Beers, Timothy C. (Department of Physics and JINA Center for the Evolution of the Elements, University of Notre Dame)
Masseron, Thomas (Instituto de Astrofisica de Canarias)
Publication Information
Journal of The Korean Astronomical Society / v.55, no.2, 2022 , pp. 23-36 More about this Journal
Abstract
We present a method to determine nitrogen abundance ratios with respect to iron ([N/Fe]) from molecular CN-band features observed in low-resolution (R ~ 2000) stellar spectra obtained by the Sloan Digital Sky Survey (SDSS) and the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). Various tests are carried out to check the systematic and random errors of our technique, and the impact of signal-to-noise (S/N) ratios of stellar spectra on the determined [N/Fe]. We find that the uncertainty of our derived [N/Fe] is less than 0.3 dex for S/N ratios larger than 10 in the ranges Teff = [4000, 6000] K, log g = [0.0, 3.5], [Fe/H] = [-3.0, 0.0], [C/Fe] = [-1.0, +4.5], and [N/Fe] = [-1.0, +4.5], the parameter space that we are interested in to identify N-enhanced stars in the Galactic halo. A star-by-star comparison with a sample of stars with [N/Fe] estimates available from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) also suggests a similar level of uncertainty in our measured [N/Fe], after removing its systematic error. Based on these results, we conclude that our method is able to reproduce [N/Fe] from low-resolution spectroscopic data, with an uncertainty sufficiently small to discover N-rich stars that presumably originated from disrupted Galactic globular clusters.
Keywords
methods: data analysis; techniques: spectroscopic; Galaxy: halo; stars: abundances;
Citations & Related Records
연도 인용수 순위
  • Reference
1 Majewski, S. R., Schiavon, R. P., Frinchaboy, P. M., et al. 2017, The Apache Point Observatory Galactic Evolution Experiment (APOGEE), AJ, 154, 94   DOI
2 Gustafsson, B., Edvardsson, B., Eriksson, K., et al. 2008, A grid of MARCS model atmospheres for late-type stars. I. Methods and general properties, A&A, 486, 951   DOI
3 Helmi, A., Babusiaux, C., Koppelman, H. H., et al. 2018, The merger that led to the formation of the Milky Way's inner stellar halo and thick disk, NATURE, 563, 85   DOI
4 Horta, D., Mackereth, J. T., Schiavon, R. P., et al. 2021, The contribution of N-rich stars to the Galactic stellar halo using APOGEE red giants, MNRAS, 500, 5462
5 Kayser, A., Hilker, M., Grebel, E. K., & Willemsen, P. G. 2008, Comparing CN and CH line strengths in a homogeneous spectroscopic sample of 8 Galactic globular clusters, A&A, 486, 437   DOI
6 Koppelman, H. H., Helmi, A., Massari, D., Price-Whelan, A. M., & Starkenburg, T. K. 2019, Multiple retrograde substructures in the Galactic halo: A shattered view of Galactic history, A&A, 631, L9   DOI
7 Kupka, F., Piskunov, N., Ryabchikova, T. A., Stempels, H. C., & Weiss, W. W. 1999, VALD-2: Progress of the Vienna Atomic Line Data Base, A&AS, 138, 119   DOI
8 Lee, Y. S., Beers, T. C., Sivarani, T., et al. 2008a, The SEGUE Stellar Parameter Pipeline. I. Description and Comparison of Individual Methods, AJ, 136, 2022   DOI
9 Lee, Y. S., Beers, T. C., Allende Prieto, C., et al. 2011, The SEGUE Stellar Parameter Pipeline. V. Estimation of Alpha-element Abundance Ratios from Low-resolution SDSS/SEGUE Stellar Spectra, AJ, 141, 90   DOI
10 Lee, Y. S., Beers, T. C., Masseron, T., et al. 2013, Carbon-enhanced Metal-poor Stars in SDSS/SEGUE. I. Carbon Abundance Estimation and Frequency of CEMP Stars, AJ, 146, 132   DOI
11 Carretta, E. 2016, Globular clusters and their contribution to the formation of the Galactic halo, The General Assembly of Galaxy Halos: Structure, Origin and Evolution, 317, 97
12 York, D. G., Adelman, J., Anderson, J. E., et al. 2000, The Sloan Digital Sky Survey: Technical Summary, AJ, 120, 1579   DOI
13 Ahumada, R., Prieto, C. A., Almeida, A., et al. 2020, The 16th Data Release of the Sloan Digital Sky Surveys: First Release from the APOGEE-2 Southern Survey and Full Release of eBOSS Spectra, ApJS, 249, 3   DOI
14 Bailer-Jones, C. A. L. 2000, Stellar parameters from very low resolution spectra and medium band filters. Teff, log g and [M/H] using neural networks, A&A, 357, 197
15 Lardo, C., Battaglia, G., Pancino, E., et al. 2016, Carbon and nitrogen abundances of individual stars in the Sculptor dwarf spheroidal galaxy, A&A, 585, A70   DOI
16 Abolfathi, B., Aguado, D. S., Aguilar, G., et al. 2018, The Fourteenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the Extended Baryon Oscillation Spectroscopic Survey and from the Second Phase of the Apache Point Observatory Galactic Evolution Experiment, ApJS, 235, 42   DOI
17 Bastian, N., & Lardo, C. 2018, Multiple Stellar Populations in Globular Clusters, ARA&A, 56, 83   DOI
18 Allende Prieto, C., Beers, T. C., Wilhelm, R., et al. 2006, A Spectroscopic Study of the Ancient Milky Way: F- and G-Type Stars in the Third Data Release of the Sloan Digital Sky Survey, ApJ, 636, 804   DOI
19 Allende Prieto, C., Sivarani, T., Beers, T. C., et al. 2008, The SEGUE Stellar Parameter Pipeline. III. Comparison with High-Resolution Spectroscopy of SDSS/SEGUE Field Stars, AJ, 136, 2070   DOI
20 Asplund, M., Grevesse, N., & Sauval, A. J. 2005, The Solar Chemical Composition, Cosmic Abundances as Records of Stellar Evolution and Nucleosynthesis, 336, 25
21 Martell, S. L., & Grebel, E. K. 2010, Light-element abundance variations in the Milky Way halo, A&A, 519, A14   DOI
22 Martell, S. L., Smolinski, J. P., Beers, T. C., & Grebel, E. K. 2011, Building the Galactic halo from globular clusters: evidence from chemically unusual red giants, A&A, 534, A136   DOI
23 Masseron, T., Plez, B., Primas, F., Van Eck, S., & Jorissen, A. 2006, A VLT-UVES spectrscopic analysis of C-rich Fe-poor stars, PhD thesis, Observatoire de Paris, France
24 Myeong, G. C., Evans, N. W., Belokurov, V., Sanders, J. L., & Koposov, S. E. 2018, Discovery of new retrograde substructures: the shards of ω Centauri ?, MNRAS, 478, 5449   DOI
25 Plez, B. 2012, Turbospectrum: Code for spectral synthesis, Astrophysics Source Code Library, ascl:1205.004
26 Belokurov, V., Erkal, D., Evans, N. W., Koposov, S. E., & Deason, A. J. 2018, Co-formation of the disc and the stellar halo, MNRAS, 478, 611   DOI
27 Smolinski, J. P., Martell, S. L., Beers, T. C., & Lee, Y. S. 2011b, A Survey of CN and CH Variations in Galactic Globular Clusters from Sloan Digital Sky Survey Spectroscopy, AJ, 142, 126   DOI
28 Carretta, E., Bragaglia, A., Gratton, R. G., et al. 2009, NaO anticorrelation and HB. VII. The chemical composition of first and second-generation stars in 15 globular clusters from GIRAFFE spectra, A&A, 505, 117   DOI
29 Schiavon, R. P., Zamora, O., Carrera, R., et al. 2017, Chemical tagging with APOGEE: discovery of a large population of N-rich stars in the inner Galaxy, MNRAS, 465, 501   DOI
30 Smith, V. V., Cunha, K., Shetrone, M. D., et al. 2013, Chemical Abundances in Field Red Giants from High-resolution H-band Spectra Using the APOGEE Spectral Linelist, ApJ, 765, 16   DOI
31 Suda, T., Katsuta, Y., Yamada, S., et al. 2008, Stellar Abundances for the Galactic Archeology (SAGA) Database - Compilation of the Characteristics of Known Extremely Metal-Poor Stars, PASJ, 60, 1159   DOI
32 Fernandez-Trincado, J. G., Beers, T. C., Queiroz, A. B. A., et al. 2021b, APOGEE-2 Discovery of a Large Population of Relatively High-Metallicity Globular Cluster Debris, ApJ, 918, L37   DOI
33 Luo, A.-L., Zhao, Y.-H., Zhao, G., & et al. 2019, VizieR Online Data Catalog: LAMOST DR5 catalogs (Luo+, 2019), VizieR Online Data Catalog, V/164
34 Carollo, D., Martell, S. L., Beers, T. C., & Freeman, K. C. 2013, CN Anomalies in the Halo System and the Origin of Globular Clusters in the Milky Way, ApJ, 769, 87   DOI
35 Alam, S., Albareti, F. D., Allende Prieto, C., et al. 2015, The Eleventh and Twelfth Data Releases of the Sloan Digital Sky Survey: Final Data from SDSS-III, ApJS, 219, 12   DOI
36 Alvarez, R., & Plez, B. 1998, Near-infrared narrow-band photometry of M-giant and Mira stars: models meet observations, A&A, 330, 1109
37 Barklem, P. S., & O'Mara, B. J. 1998, The broadening of strong lines of Ca+, Mg+ and Ba+ by collisions with neutral hydrogen atoms, MNRAS, 300, 863   DOI
38 Collet, R., Asplund, M., & Trampedach, R. 2007, Three-dimensional hydrodynamical simulations of surface convection in red giant stars, A&A, 469, 687   DOI
39 Fernandez-Trincado, J. G., Beers, T. C., Minniti, D., et al. 2020b, Discovery of a Large Population of Nitrogen-Enhanced Stars in the Magellanic Clouds, ApJ, 903, L17   DOI
40 Gaia Collaboration, Brown, A. G. A., Vallenari, A., et al. 2018, Gaia Data Release 2. Summary of the contents and survey properties, A&A, 616, A1   DOI
41 Koch, A., Grebel, E. K., & Martell, S. L. 2019, Purveyors of fine halos: Re-assessing globular cluster contributions to the Milky Way halo buildup with SDSS-IV, A&A, 625, A75   DOI
42 Lee, Y. S., Beers, T. C., Sivarani, T., et al. 2008b, The SEGUE Stellar Parameter Pipeline. II. Validation with Galactic Globular and Open Clusters, AJ, 136, 2050   DOI
43 Lee, Y. S., Beers, T. C., Carlin, J. L., et al. 2015, Application of the SEGUE Stellar Parameter Pipeline to LAMOST Stellar Spectra, AJ, 150, 187   DOI
44 Hill, V., Plez, B., Cayrel, R., et al. 2002, First stars. I. The extreme r-element rich, iron-poor halo giant CS 31082-001. Implications for the r-process site(s) and radioactive cosmochronology, A&A, 387, 560   DOI
45 Demarque, P., Woo, J.-H., Kim, Y.-C., & Yi, S. K. 2004, Y2 Isochrones with an Improved Core Overshoot Treatment, ApJS, 155, 667   DOI
46 Fernandez-Trincado, J. G., Beers, T. C., Placco, V. M., et al. 2019b, Discovery of a New Stellar Sub-Population Residing in the (Inner) Stellar Halo of the Milky Way, ApJ, 886, L8   DOI
47 Fernandez-Trincado, J. G., Minniti, D., Beers, T. C.,, et al. 2020a, The Enigmatic Globular Cluster UKS 1 Obscured by the Bulge: H-band Discovery of Nitrogen-Enhanced Stars, A&A, 643, 145
48 Fernandez-Trincado, J. G., Beers, T. C., Minniti, D., et al. 2021a, APOGEE Discovery of a Chemically Atypical Star Disrupted from NGC 6723 and Captured by the Milky Way Bulge, A&A, 647, 64
49 Re Fiorentin, P., Bailer-Jones, C. A. L., Lee, Y. S., et al. 2007, Estimation of stellar atmospheric parameters from SDSS/SEGUE spectra, A&A, 467, 1373   DOI
50 Cui, X.-Q., Zhao, Y.-H., Chu, Y.-Q., et al. 2012, The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), RAA, 12, 1197
51 Smolinski, J. P., Lee, Y. S., Beers, T. C., et al. 2011, The SEGUE Stellar Parameter Pipeline. IV. Validation with an Extended Sample of Galactic Globular and Open Clusters, AJ, 141, 89   DOI
52 Martell, S. L., Shetrone, M. D., Lucatello, S., et al. 2016, Chemical Tagging in the SDSS-III/APOGEE Survey: New Identifications of Halo Stars with Globular Cluster Origins, ApJ, 825, 146   DOI
53 Masseron, T., Plez, B., Van Eck, S., et al. 2014, CH in stellar atmospheres: an extensive linelist, A&A, 571, A47   DOI
54 Naidu, R. P., Conroy, C., Bonaca, A., et al. 2020, Evidence from the H3 Survey That the Stellar Halo Is Entirely Comprised of Substructure, ApJ, 901, 48   DOI
55 Markwardt, C. B. 2009, Non-linear Least-squares Fitting in IDL with MPFIT, Astronomical Data Analysis Software and Systems XVIII, 411, 251
56 Martin, Nicolas F., Venn, Kim A., Aguado, David S., et al. 2022, A stellar stream remnant of a globular cluster below the metallicity floor, NATURE, 601, 45   DOI
57 Myeong, G. C., Vasiliev, E., Iorio, G., Evans, N. W., & Belokurov, V. 2019, Evidence for two early accretion events that built the Milky Way stellar halo, MNRAS, 488, 1235   DOI
58 Fernandez-Trincado, J. G., Zamora, O., Souto, D., et al. 2019a, H-Band Discovery of Additional Second-Generation Stars in the Galactic Bulge Globular Cluster NGC 6522 as Observed by APOGEE and Gaia, A&A, 627, 178
59 Tang, B., Fern'andez-Trincado, J. G., Liu, C., et al. 2020, On the Chemical and Kinematic Consistency between N-rich Metal-poor Field Stars and Enriched Populations in Globular Clusters, ApJ, 891, 28   DOI
60 Yanny, B., Rockosi, C., Newberg, H. J., et al. 2009, SEGUE: A Spectroscopic Survey of 240,000 Stars with g = 14-20, AJ, 137, 4377   DOI
61 Lardo, C., Milone, A. P., Marino, A. F., et al. 2012, C and N abundances of main sequence and subgiant branch stars in NGC 1851, A&A, 541, A141   DOI