Calculation of Rate Coefficients for Electron Capture in Collisions of O<sup>2+</sup>and N<sup>2+</sup>Ions with H

Barragán, Patricia; Errea, L. F.; Méndez, L.; Rabadán, I.; Riéra, Antoni

doi:10.1086/497884

Cited by 13 publications

(6 citation statements)

References 34 publications

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“…The adopted table for radiative and dielectronic recombinations is limited to the 11 sequences that are H-like−Na-like (Badnell 2006 Barragán et al (2006).…”

Section: D3 Miscellaneous Datamentioning

confidence: 99%

Heating of blue compact dwarf galaxies: gas distribution and photoionization by stars in I Zw 18

Pequignot

2007

A&A

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Aims. Photoionization models so far are unable to account for the high electron temperature T e ([O iii]) implied by the line intensity ratio [O iii]λ4363 Å/[O iii]λ5007 Å in low-metallicity blue compact dwarf galaxies, casting doubt on the assumption of photoionization by hot stars as the dominant source of heating of the gas in these objects of large cosmological significance. Methods. Combinations of runs of the 1D photoionization code NEBU are used to explore alternative models for the prototype giant H ii region shell I Zw 18 NW, with no reference to the filling factor concept and with due consideration for geometrical and stellar evolution constraints.Results. Acceptable models for I Zw 18 NW are obtained, which represent schematically an incomplete shell comprising radiationbounded condensations embedded in a low-density matter-bounded diffuse medium. The thermal pressure contrast between gas components is about a factor 7. The diffuse phase can be in pressure balance with the hot superbubble fed by mechanical energy from the inner massive star cluster. The failure of previous models is ascribed to (1) the adoption of an inadequate small-scale gas density distribution, which proves critical when the collisional excitation of hydrogen contributes significantly to the cooling of the gas, and possibly (2) a too restrictive implementation of Wolf-Rayet stars in synthetic stellar cluster spectral energy distributions. A neutral gas component heated by soft X-rays, whose power is less than 1% of the star cluster luminosity and consistent with CHANDRA data, can explain the low-ionization fine-structure lines detected by SPITZER. [O/Fe]

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“…The adopted table for radiative and dielectronic recombinations is limited to the 11 sequences that are H-like−Na-like (Badnell 2006 Barragán et al (2006).…”

Section: D3 Miscellaneous Datamentioning

confidence: 99%

Heating of blue compact dwarf galaxies: gas distribution and photoionization by stars in I Zw 18

Pequignot

2007

A&A

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“…Certain rates, for example those of low ionisation states of oxygen, have been updated in CLOUDY. We have updated the rate equations for oxygen charge exchange reactions to match those from the most recent version (v17.02) of the CLOUDY source code (Stancil et al 1999;Barragán et al 2006). For all others, we rely on Kingdon & Ferland (1996) 2 .…”

Section: Chemistrymentioning

confidence: 99%

RAMSES-RTZ: Non-Equilibrium Metal Chemistry and Cooling Coupled to On-The-Fly Radiation Hydrodynamics

Katz

2022

Preprint

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Emission and absorption lines from elements heavier than helium (metals) represent one of our strongest probes of galaxy formation physics across nearly all redshifts accessible to observations. The vast majority of simulations that model these metal lines often assume either collisional or photoionisation equilibrium, or a combination of the two. For the few simulations that have relaxed these assumptions, a redshift-dependent meta-galactic UV background or fixed spectrum is often used in the nonequilibrium photoionisation calculation, which is unlikely to be accurate in the interstellar medium where the gas can self-shield as well as in the high-redshift circumgalactic medium where locally emitted radiation may dominate over the UV background. In this work, we relax this final assumption by coupling the ionisation states of individual metals to the radiation hydrodynamics solver present in RAMSES-RT. Our chemical network follows radiative recombination, dielectronic recombination, collisional ionisation, photoionisation, and charge transfer and we use the ionisation states to compute non-equilibrium optically-thin metalline cooling. The fiducial model solves for the ionisation states of C, N, O, Mg, Si, S, Fe, and Ne in addition to H, He, and H 2 , but can be easily extended for other ions. We provide interfaces to two different ODE solvers that are competitive in both speed and accuracy. The code has been benchmarked across a variety of gas conditions to reproduce results from CLOUDY when equilibrium is reached. We show an example isolated galaxy simulation with on-the-fly radiative transfer that demonstrates the utility of our code for translating between simulations and observations without the use of idealised photoionisation models.

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“…Since the region in which metastable ionisation for oxygen becomes notable is 40 eV and the threshold for the transition in nitrogen is higher, it is, therefore, assumed that metastable transitions from N ii to N i will only be relevant for temperatures far above that of the solar atmosphere. Barragán et al (2006) considered CT from the ground and metastable levels of N iii, and their rate coefficients are included here. CT ionisation out of N ii is not relevant because CT from N iii recombines into levels which decay on timescales far shorter than CT ionisation rates.…”

Section: Charge Transfermentioning

confidence: 99%

Modelling low charge ions in the solar atmosphere

Dufresne,

Del Zanna,

Storey

2021

Preprint

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Extensions have been made recently to the coronal approximation for the purpose of modelling line emission from carbon and oxygen in the lower solar atmosphere. The same modelling is used here for other elements routinely observed in the solar transition region: N, Ne, Mg, Si and S. The modelling includes the effects of higher densities suppressing dielectronic recombination and populating long-lived, metastable levels; the presence of metastable levels typically causes effective ionisation rates to increase and recombination rates to decrease. Processes induced by the radiation field, namely photo-ionisation and photo-excitation, have been included, along with charge transfer, which occurs when electrons are exchanged during atom-ion and ion-ion collisions. The resulting ion balances are shown, and indicate significant changes compared to the frequently-employed coronal approximation. The effect on level populations within ions caused by photo-excitation is also assessed. To give an illustration of how line emission could be altered by these processes, selected line contribution functions are presented at the end.

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Calculation of Rate Coefficients for Electron Capture in Collisions of O²⁺and N²⁺Ions with H

Cited by 13 publications

References 34 publications

Heating of blue compact dwarf galaxies: gas distribution and photoionization by stars in I Zw 18

Heating of blue compact dwarf galaxies: gas distribution and photoionization by stars in I Zw 18

RAMSES-RTZ: Non-Equilibrium Metal Chemistry and Cooling Coupled to On-The-Fly Radiation Hydrodynamics

Modelling low charge ions in the solar atmosphere

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Calculation of Rate Coefficients for Electron Capture in Collisions of O2+and N2+Ions with H

Cited by 13 publications

References 34 publications

Heating of blue compact dwarf galaxies: gas distribution and photoionization by stars in I Zw 18

Heating of blue compact dwarf galaxies: gas distribution and photoionization by stars in I Zw 18

RAMSES-RTZ: Non-Equilibrium Metal Chemistry and Cooling Coupled to On-The-Fly Radiation Hydrodynamics

Modelling low charge ions in the solar atmosphere

Contact Info

Product

Resources

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Calculation of Rate Coefficients for Electron Capture in Collisions of O²⁺and N²⁺Ions with H