| 1. |
- de Jong, R. S., et al.
(författare)
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4MOST : Project overview and information for the First Call for Proposals
- 2019
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Ingår i: The Messenger. - : European Southern Observatory. - 0722-6691. ; 175, s. 3-11
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We introduce the 4-metre Multi-Object Spectroscopic Telescope (4MOST), a new high-multiplex, wide-field spectroscopic survey facility under development for the four-metre-class Visible and Infrared Survey Telescope for Astronomy (VISTA) at Paranal. Its key specifications are: a large field of view (FoV) of 4.2 square degrees and a high multiplex capability, with 1624 fibres feeding two low-resolution spectrographs (R = λ/Δλ ~ 6500), and 812 fibres transferring light to the high-resolution spectrograph (R ~ 20 000). After a description of the instrument and its expected performance, a short overview is given of its operational scheme and planned 4MOST Consortium science; these aspects are covered in more detail in other articles in this edition of The Messenger. Finally, the processes, schedules, and policies concerning the selection of ESO Community Surveys are presented, commencing with a singular opportunity to submit Letters of Intent for Public Surveys during the first five years of 4MOST operations.
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| 2. |
- Blanton, Michael R., et al.
(författare)
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Sloan Digital Sky Survey IV : Mapping the Milky Way, Nearby Galaxies, and the Distant Universe
- 2017
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Ingår i: Astronomical Journal. - : IOP Publishing Ltd. - 0004-6256 .- 1538-3881. ; 154:1
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Tidskriftsartikel (refereegranskat)abstract
- We describe the Sloan Digital Sky Survey IV (SDSS-IV), a project encompassing three major spectroscopic programs. The Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2) is observing hundreds of thousands of Milky Way stars at high resolution and. high signal-to-noise ratios in the near-infrared. The Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey is obtaining spatially resolved spectroscopy for thousands of nearby galaxies (median z similar to 0.03). The extended Baryon Oscillation Spectroscopic Survey (eBOSS) is mapping the galaxy, quasar, and neutral gas distributions between z similar to 0.6 and 3.5 to constrain cosmology using baryon acoustic oscillations, redshift space distortions, and the shape of the power spectrum. Within eBOSS, we are conducting two major subprograms: the SPectroscopic IDentification of eROSITA Sources (SPIDERS), investigating X-ray AGNs. and galaxies in X-ray clusters, and the Time Domain Spectroscopic Survey (TDSS), obtaining spectra of variable sources. All programs use the 2.5 m Sloan Foundation Telescope at the. Apache Point Observatory; observations there began in Summer 2014. APOGEE-2 also operates a second near-infrared spectrograph at the 2.5 m du Pont Telescope at Las Campanas Observatory, with observations beginning in early 2017. Observations at both facilities are scheduled to continue through 2020. In keeping with previous SDSS policy, SDSS-IV provides regularly scheduled public data releases; the first one, Data Release 13, was made available in 2016 July.
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| 3. |
- Abolfathi, Bela, et al.
(författare)
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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
- 2018
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Ingår i: Astrophysical Journal Supplement Series. - : IOP Publishing Ltd. - 0067-0049 .- 1538-4365. ; 235:2
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Tidskriftsartikel (refereegranskat)abstract
- The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) has been in operation since 2014 July. This paper describes the second data release from this phase, and the 14th from SDSS overall (making this Data Release Fourteen or DR14). This release makes the data taken by SDSS-IV in its first two years of operation (2014-2016 July) public. Like all previous SDSS releases, DR14 is cumulative, including the most recent reductions and calibrations of all data taken by SDSS since the first phase began operations in 2000. New in DR14 is the first public release of data from the extended Baryon Oscillation Spectroscopic Survey; the first data from the second phase of the Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE-2), including stellar parameter estimates from an innovative data-driven machine-learning algorithm known as "The Cannon"; and almost twice as many data cubes from the Mapping Nearby Galaxies at APO (MaNGA) survey as were in the previous release (N = 2812 in total). This paper describes the location and format of the publicly available data from the SDSS-IV surveys. We provide references to the important technical papers describing how these data have been taken (both targeting and observation details) and processed for scientific use. The SDSS web site (www.sdss.org) has been updated for this release and provides links to data downloads, as well as tutorials and examples of data use. SDSS-IV is planning to continue to collect astronomical data until 2020 and will be followed by SDSS-V.
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| 4. |
- Zhang, X. H., et al.
(författare)
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Benchmarking Multiconfiguration Dirac-Hartree-Fock Calculations for Astrophysics : Si-like Ions from Cr xi to Zn xvii
- 2021
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Ingår i: Astrophysical Journal Supplement Series. - : Institute of Physics Publishing (IOPP). - 0067-0049 .- 1538-4365. ; 257:2
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Tidskriftsartikel (refereegranskat)abstract
- The multiconfiguration Dirac-Hartree-Fock (MCDHF) and relativistic configuration interaction methods are used to provide excitation energies, lifetimes, and radiative transition data for the 604 (699, 702, 704, 704, 704, and 699) lowest levels of the 3s (2)3p (2), 3s3p (3), 3s (2)3p3d, 3p (4), 3s3p (2)3d, 3s (2)3d (2), 3p (3)3d, 3s3p3d (2), 3s3d (3), 3p3d (3), 3p (2)3d (2), 3s (2)3p4s, 3s (2)3p4p, 3s (2)3p4d, 3s (2)3p4f, 3s3p (2)4s, 3s3p (2)4p, 3s3p (2)4d, 3s3p (2)4f, 3s (2)3d4s, 3s (2)3d4p, 3p (3)4s, 3p (3)4p, 3s3p3d4s, 3s (2)3p5s, and 3s (2)3p5p configurations in Cr xi, (Mn xii, Fe xiii, Co xiv, Ni xv, Cu xvi, and Zn xvii). Previous line identifications of Fe xiii and Ni xv in the EUV and X-ray wavelength ranges are reviewed by comprehensively comparing the MCDHF theoretical results with available experimental data. Many recent identifications of Fe xiii and Ni xv lines are confirmed, and several new identifications for these two ions are proposed. A consistent atomic data set with spectroscopic accuracy is provided for the lowest hundreds of levels for Si-like ions of iron-group elements of astrophysical interest, for which experimental values are scarce. The uncertainty estimation method suggested by Kramida, applied to the comparison of the length and velocity line strength values, is used for ranking the transition data. The correlation of the latter with the gauge dependency patterns of the line strengths is investigated.
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| 5. |
- Song, C.X., et al.
(författare)
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Large-scale multiconfiguration Dirac-Hartree-Fock calculations for astrophysics : n=4 levels in P-like ions from Mn XIto Ni XIV
- 2020
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Ingår i: Astrophysical Journal Supplement Series. - : Institute of Physics (IOP). - 0067-0049 .- 1538-4365. ; 247:70, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- Using the multiconfiguration Dirac–Hartree–Fock and the relativistic configuration interaction methods, a consistent set of transition energies and radiative transition data for the lowest 546 (623, 701, and 745) states of the , , , , , , , , , , , , , , , and configurations in Mn xi (Fe xii, Co xiii, and Ni xiv) is provided. The comparison between calculated excitation energies for the n = 4 states and available experimental values for Fe xii indicate that the calculations are highly accurate, with uncertainties of only a few hundred cm−1. Lines from these states are prominent in the soft X-rays. With the present calculations, several recent new identifications are confirmed. Other identifications involving levels in Fe xii that were found to be questionable are discussed and a few new assignments are recommended. As some n = 4 states of the other ions also show large discrepancies between experimental and calculated energies, we reassess their identification. The present study provides highly accurate atomic data for the n = 4 states of P-like ions of astrophysical interest, for which experimental data are scarce.
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| 6. |
- Wang, Kai, et al.
(författare)
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Extended calculations of energy levels, radiative properties, A(J), B-J hyperfine interaction constants, and Lande g(J)-factors for nitrogen-like Ge XXVI
- 2018
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Pergamon Press. - 0022-4073 .- 1879-1352. ; 208, s. 134-151
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Tidskriftsartikel (refereegranskat)abstract
- Employing two state-of-the-art methods, multiconfiguration Dirac-Hartree-Fock and second-order many body perturbation theory, highly accurate calculations are performed for the lowest 272 fine -structure levels arising from the 2s(2)2p(3), 2s(2)p(4), 2p(5), 2s(2)2p(2)3l (l = s, p, d), 2s2p(3)3l (l = s, p, d), and 2p(4)3l (l = s, p. d) configurations in nitrogen-like Ge XXVI. Complete and consistent atomic data, including excitation energies, lifetimes, wavelengths, hyperfine structures, Lande g(J)-factors, and E1, E2, M1, M2 line strengths, oscillator strengths, and transition rates among these 272 levels are provided. Comparisons are made between the present two data sets, as well as with other available experimental and theoretical values. The present data are accurate enough for identification and deblending of emission lines involving the n = 3 levels, and are also useful for modeling and diagnosing fusion plasmas. (C) 2018 Elsevier Ltd. All rights reserved.
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