<i>J</i>‐Resolved He<scp>i</scp>Emission Predictions in the Low‐Density Limit

Bauman, Robert P.; Porter, R. L.; Ferland, Gary J.; MacAdam, K. B.

doi:10.1086/430665

Cited by 45 publications

(73 citation statements)

References 35 publications

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“…To determine He + /H + , we used three observed lines of He i at λλ4471, 5876 and 6678, weighted by 1:3:1. Case B He i emissivities were taken from the collision -less (low-density limit) calculations by Bauman et al (2005). We used a J-resolved code available on-line 2 for these calculations.…”

Section: Ionic and Total Abundancesmentioning

confidence: 99%

Chemical behavior of the dwarf irregular galaxy NGC6822. Its PN and HII region abundances

Hernández-Martínez

Peña²,

Carigi

et al. 2009

A&A

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Aims. We aim to derive the chemical behavior of a significant sample of PNe and HII regions in the irregular galaxy NGC 6822. The selected objects are distributed in different zones of the galaxy. Our purpose is to obtain the chemical abundances of the present interstellar medium (ISM), represented by H ii regions, and the corresponding values at the time of formation of PNe. With these data the chemical homogeneity of NGC 6822 were tested and the abundance pattern given by H ii regions and PNe used as an observational constraint for computing chemical evolution models to infer the chemical history of NGC 6822.Methods. Due to the faintness of PNe and H ii regions in NGC 6822, to gather spectroscopic data with large telescopes is necessary.We obtained a well suited sample of spectra by employing VLT-FORS 2 and Gemini-GMOS spectrographs. Ionic and total abundances were calculated for the objects where electron temperatures could determined through the detection of [O iii] λ4363 or/and [N ii] λ5755 lines. A "simple" chemical evolution model was developed and the observed data were used to compute a model for NGC 6822 in order to infer a preliminary chemical history in this galaxy.Results. Confident determinations of He, O, N, Ne, S and Ar abundances were derived for a sample of 11 PNe and one H ii region. We confirm that the present ISM is chemically homogeneous, at least in the central 2 kpc of the galaxy, showing a value 12 + log O/H = 8.06 ± 0.04. From the abundance pattern of PNe, we identified two populations: a group of young PNe with abundances similar to H ii regions and a group of older objects with abundances a factor of two lower. A pair of extreme Type I PNe were found. No third dredge-up O enrichement was detected in PNe of this galaxy. The abundance determinations allow us to discuss the chemical behavior of the present and past ISM in NGC 6822. Our preliminary chemical evolution model predicts that an important gas-mass loss occurred during the first 5.3 Gyr, that no star higher than 40 M was formed, and that 1% of all 3-15 M stars became binary system progenitors of SNIa.

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Section: Ionic and Total Abundancesmentioning

confidence: 99%

Chemical behavior of the dwarf irregular galaxy NGC6822. Its PN and HII region abundances

Hernández-Martínez

Peña²,

Carigi

et al. 2009

A&A

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“…Recent atomic calculations for the two-electron system 4 He i (Benjamin et al 1999;Bauman et al 2005;Porter et al 2007) are in good agreement. Remaining issues include collisional processes involving the ground or metastable levels, photoionization cross sections for non-hydrogenic moderate-n, small-l levels and transition probabilities for these levels (Porter et al 2009).…”

Section: Cosmology and Fundamental Physicsmentioning

confidence: 60%

The impact of recent advances in laboratory astrophysics on our understanding of the cosmos

et al. 2012

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Abstract. An emerging theme in modern astrophysics is the connection between astronomical observations and the underlying physical phenomena that drive our cosmos. Both the mechanisms responsible for the observed astrophysical phenomena and the tools used to probe such phenomena -the radiation and particle spectra we observe -have their roots in atomic, molecular, condensed matter, plasma, nuclear and particle physics. Chemistry is implicitly included in both molecular and condensed matter physics. This connection is the theme of the present report, which provides a broad, though non-exhaustive, overview of progress in our understanding of the cosmos resulting from recent theoretical and experimental advances in what is commonly called laboratory astrophysics. This work, carried out by a diverse community of laboratory astrophysicists, is increasingly important as astrophysics transitions into an era of precise measurement and high fidelity modeling.

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“…Yet, this is not at the 1% accuracy level needed to place useful constrains on the primordial helium abundance in cosmological studies [9,10]. Recently, Bauman et al [6] worked out the recombination problem in fine structure in the low density limit. They found no significant effects on the recombination spectrum from spin-orbit coupling.…”

Section: Heliummentioning

confidence: 99%

Atomic processes in planetary nebulae and H ii regions

Bautista¹

2009

Phys. Scr.

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Abstract. Spectroscopic studies of Planetary Nebulae (PNe) and H ii regions have driven much development in atomic physics. In the last few years the combination of a generation of powerful observatories, the development of ever more sophisticated spectral modeling codes, and large efforts on mass production of high quality atomic data have led to important progress in our understanding of the atomic spectra of such astronomical objects. In this paper I review such progress, including evaluations of atomic data by comparisons with nebular spectra, detection of spectral lines from most iron-peak elements and n-capture elements, observations of hyperfine emission lines and analysis of isotopic abundances, fluorescent processes, and new techniques for diagnosing physical conditions based on recombination spectra. The review is directed toward atomic physicists and spectroscopists trying to establish the current status of the atomic data and models and to know the main standing issues. IntroductionNearly all modern observational research in gaseous nebulae (PNe, H ii regions, and circumstellar nebulae) involves some kind of spectra, whose interpretation requires some understanding of the atomic processes involved and the handling of atomic data. The level of understanding of such processes and the data required for various applications ranges from phenomenological and statistical studies of commonly prominent lines, to compilation of raw atomic data for direct inspection (such as line finding lists), and to modeling of synthetic spectra attempting to fit the observed spectra. On the other hand, the accuracy and quantity of atomic models describing various features in observed spectra have evolved with time, driven by great advances in ground-and space-based observatories, computer technology and experimental techniques. At present there are models and data accurate enough for satisfactory analysis of at least the most prominent spectral features. Also the advent of on-line databases and spectroscopic tools has revolutionized the dissemination of results of atomic physics research. However, the demands on the quantity and quality of the atomic data will grow as new instruments delivering greater sensitivity and spectral resolution become available.A review of atomic processes spans an audience that includes specialists in the study of atomic systems with tools capable of providing models and atomic data, nebular astrophysicists, astronomers seeking to understand the reliability and accuracy of their modeled spectra, and those who use the models and data to compare synthetic spectra with observations, diagnose the physical conditions and compute chemical abundances of nebulae. The present review is

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J‐Resolved HeiEmission Predictions in the Low‐Density Limit

Cited by 45 publications

References 35 publications

Chemical behavior of the dwarf irregular galaxy NGC6822. Its PN and HII region abundances

Chemical behavior of the dwarf irregular galaxy NGC6822. Its PN and HII region abundances

The impact of recent advances in laboratory astrophysics on our understanding of the cosmos

Atomic processes in planetary nebulae and H ii regions

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