Upgrading electron temperature and electron density diagnostic diagrams of forbidden line emission

Proxauf, Bastian; Öttl, S.; Kimeswenger, S.

doi:10.1051/0004-6361/201322581

Cited by 111 publications

(104 citation statements)

References 13 publications

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“…In the context of fluorescence, it is useful to discuss the recent results by Proxauf et al (2014), who claim that the usual relation between the electron temperature and the [O ] line ratio R = λλ(5007+4959)/λ4363 (as computed, for instance, by PyNeb) is biased and should be revised. The new relation they propose would lead to a decrease in the electron temperature computed from a given ratio R, compared to what would be obtained with the standard relation, with the discrepancy between both relations increasing with the electron temperature (see their Fig.…”

Section: Limitations and Caveatsmentioning

confidence: 99%

“…(3) of Liu et al 2000) by the same factor and, consequently, an artificial decrease in the diagnostic line ratio at a given electron temperature. In real nebulae, the contribution of recombination to this line is invariably much smaller than the contribution determined by Proxauf et al (2014) Similarly, PyNeb is a local code, so it is not designed to solve radiation transfer. This does not hinder interpretation of observed lines since, when optical depths are low -which is true for most of these lines -photons freely escape, and there is no need of a detailed treatment of radiation transfer.…”

Section: Limitations and Caveatsmentioning

confidence: 99%

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PyNeb: a new tool for analyzing emission lines

Luridiana

Morisset

Shaw

2014

A&A

527

409

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Analysis of emission lines in gaseous nebulae yields direct measures of physical conditions and chemical abundances and is the cornerstone of nebular astrophysics. Although the physical problem is conceptually simple, its practical complexity can be overwhelming since the amount of data to be analyzed steadily increases; furthermore, results depend crucially on the input atomic data, whose determination also improves each year. To address these challenges we created PyNeb, an innovative code for analyzing emission lines. PyNeb computes physical conditions and ionic and elemental abundances and produces both theoretical and observational diagnostic plots. It is designed to be portable, modular, and largely customizable in aspects such as the atomic data used, the format of the observational data to be analyzed, and the graphical output. It gives full access to the intermediate quantities of the calculation, making it possible to write scripts tailored to the specific type of analysis one wants to carry out. In the case of collisionally excited lines, PyNeb works by solving the equilibrium equations for an n-level atom; in the case of recombination lines, it works by interpolation in emissivity tables. The code offers a choice of extinction laws and ionization correction factors, which can be complemented by user-provided recipes. It is entirely written in the python programming language and uses standard python libraries. It is fully vectorized, making it apt for analyzing huge amounts of data. The code is stable and has been benchmarked against IRAF/NEBULAR. It is public, fully documented, and has already been satisfactorily used in a number of published papers.

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Section: Limitations and Caveatsmentioning

confidence: 99%

Section: Limitations and Caveatsmentioning

confidence: 99%

PyNeb: a new tool for analyzing emission lines

Luridiana

Morisset

Shaw

2014

A&A

527

409

View full text Add to dashboard Cite

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“…cluded from the parts of the analysis that require RO3. To estimate T e (O III) we use the fitting function from Proxauf et al (2014) that relates the temperature to RO3. The result is shown in Fig.…”

Section: Electron Density and Temperaturementioning

confidence: 99%

VLT/X-Shooter Spectroscopy of Lyman Break Analogs: Direct-method O/H Abundances and Nitrogen Enhancements

Loaiza-Agudelo

Overzier

Heckman

2020

ApJ

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We used VLT/XShooter to target a sample of nearby analogs of Lyman Break Galaxies (LBGs). These Lyman Break Analogs (LBAs) are similar to the LBGs in many of their physical properties. We determine electron temperatures using the weak [O III]λ4363 emission line, and determine the oxygen abundance (O/H) using the direct and strong line methods. We show that the direct and strong line abundances are consistent with established relations within ∼0.2 dex. The analogs have nitrogen-to-oxygen ratios (N/O) and ionization parameters (q) that are, on average, offset with respect to typical local galaxies but similar to galaxies at z ∼ 2 and other analogs. The N/O and q excesses correlate with the offsets observed in the strong line ratios, again similar to z ∼ 2. The star formation rate surface densities are consistent with the high electron density and ionization, indicating that the interstellar medium (ISM) pressure is set by feedback from the starbursts. For a given O/H, the apparent N/O excess arises due to the offset in O/H with respect to the local mass-metallicity relation. This can be explained by recent inflow of relatively metal-poor gas which lowers O/H while leaving N/O unchanged. The difficulties in determining even basic ISM parameters in these nearby analogs illustrates some of the challenges we face at much higher redshifts, where similar rest-frame optical diagnostics for large samples of galaxies can be accessed with JWST.

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“…The transition to the shell is marked by dashed lines with 1/10 and 1/100 of the peak intensity. The result reaches up to 13 000 K according to the new calibration of Proxauf et al (2014). Because of the weakness of the [O iii] λ4363 Å, which A87, page 7 of 13 Table 6).…”

Section: Density Distribution and Electron Temperaturementioning

confidence: 96%

“…The diagnostic density and temperature diagrams (described in Osterbrock &Ferland 2006 andProxauf et al 2014) provide the input and boundary conditions. Despite the strong variation in intensity, the density derived with [S ii] results in a flat distribution (Fig.…”

Section: Density Distribution and Electron Temperaturementioning

confidence: 99%

Ionization structure of multiple-shell planetary nebulae

Öttl

Kimeswenger

Zijlstra

2014

A&A

Self Cite

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Context. In recent times an increasing number of extended haloes and multiple shells around planetary nebulae have been discovered. These faint extensions to the main nebula trace the mass-loss history of the star, modified by the subsequent evolution of the nebula. Integrated models predict that some haloes may be recombining, and thus are not in ionization equilibrium. But parameters such as the ionization state and thus the contiguous excitation process are only poorly known. The haloes are very extended, but faint in surface brightness − 10 3 times lower than the main nebula. The observational limits call for an extremely well studied main nebula, to model the processes in the shells and haloes of one object. NGC 2438 is a perfect candidate to explore the physical characteristics of the halo. Aims. The aim is to derive a complete data set of the main nebula. This allows us to derive the physical conditions from photoionization models, such as temperature, density and ionization, and clumping. These models are used to derive whether the halo is in ionization equilibrium. Methods. Long-slit spectroscopic data at various positions in the nebula were obtained at the ESO 3.6 m and the SAAO 1.9 m telescope. These data were supplemented by imaging data from the HST archive and from the ESO 3.6 m telescope and by archival VLA observations. The use of diagnostic diagrams draws limits for physical properties in the models. The photoionization code CLOUDY was used to model the nebular properties and to derive a more accurate distance and ionized mass. Results. We derive an accurate extinction E B−V = 0.16, and distance of 1.9 ± 0.2 kpc. This locates the nebula behind the nearby open cluster M46 and rules out membership. The low-excitation species are found to be dominated by clumps. The emission line ratios show no evidence for shocks. The filling factor increases with radius in the nebula. The electron densities in the main nebula are ∼250 cm −3 , dropping to ∼10−30 in the shell. We find the shell in ionization equilibrium: a significant amount of UV radiation infiltrates the inner nebula. Thus the shell still seems to be ionized. The spatially resolved CLOUDY model supports the hypothesis that photoionization is the dominant process in this nebula, far out into the shell. Previous models predicted that the shell would be recombining, but this is not confirmed by the data. We note that these models used a smaller distance, and therefore different input parameters, than derived by us.

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Upgrading electron temperature and electron density diagnostic diagrams of forbidden line emission

Cited by 111 publications

References 13 publications

PyNeb: a new tool for analyzing emission lines

PyNeb: a new tool for analyzing emission lines

VLT/X-Shooter Spectroscopy of Lyman Break Analogs: Direct-method O/H Abundances and Nitrogen Enhancements

Ionization structure of multiple-shell planetary nebulae

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