Change of the relative line strengths due to the resonance induced population transfer between Fe XVII and FeXVI ions

Wu, Chensheng; Gao, Xiang

doi:10.1038/s41598-019-43916-x

Cited by 9 publications

(14 citation statements)

References 40 publications

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“…We note that for Fe xvii, the atomic data for the line are under debate, with theoretical calculations and experiments finding different values (e.g., Gu et al 2007;de Plaa et al 2012;Bernitt et al 2012;Wu & Gao 2019;Gu et al 2019). Indeed the Kaastra (2018) wavelength and oscillator strength that we use for this ion do not agree with the Verner et al (1996) values.…”

Section: Ews From the Simulated Datamentioning

confidence: 65%

The warm-hot circumgalactic medium around EAGLE-simulation galaxies and its detection prospects with X-ray and UV line absorption

Wijers

Schaye

Oppenheimer

2020

Monthly Notices of the Royal Astronomical Society

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We use the EAGLE cosmological simulation to study the distribution of baryons, and FUV (O vi), EUV (Ne viii) and X-ray (O vii, O viii, Ne ix, and Fe xvii) line absorbers, around galaxies and haloes of mass $\, \rm {M}_{\rm {200c}}= 10^{11}$–$10^{14.5} \, \rm {M}_{\odot }$ at redshift 0.1. EAGLE predicts that the circumgalactic medium (CGM) contains more metals than the interstellar medium across halo masses. The ions we study here trace the warm-hot, volume-filling phase of the CGM, but are biased towards temperatures corresponding to the collisional ionization peak for each ion, and towards high metallicities. Gas well within the virial radius is mostly collisionally ionized, but around and beyond this radius, and for O vi, photo-ionization becomes significant. When presenting observables we work with column densities, but quantify their relation with equivalent widths by analysing virtual spectra. Virial-temperature collisional ionization equilibrium ion fractions are good predictors of column density trends with halo mass, but underestimate the diversity of ions in haloes. Halo gas dominates the highest column density absorption for X-ray lines, but lower-density gas contributes to strong UV absorption lines from O vi and Ne viii. Of the O vii (O viii) absorbers detectable in an Athena X-IFU blind survey, we find that 41 (56) per cent arise from haloes with $\, \rm {M}_{\rm {200c}}= 10^{12.0 \rm {-}13.5} \, \rm {M}_{\odot }$. We predict that the X-IFU will detect O vii (O viii) in 77 (46) per cent of the sightlines passing $\, \rm {M}_{\star }= 10^{10.5 \rm {-}11.0} \, \rm {M}_{\odot }$ galaxies within $100 \, \rm {pkpc}$ (59 (82) per cent for $\, \rm {M}_{\star }> 10^{11.0} \, \rm {M}_{\odot }$). Hence, the X-IFU will probe covering fractions comparable to those detected with the Cosmic Origins Spectrograph for O vi.

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Section: Ews From the Simulated Datamentioning

confidence: 65%

The warm-hot circumgalactic medium around EAGLE-simulation galaxies and its detection prospects with X-ray and UV line absorption

Wijers

Schaye

Oppenheimer

2020

Monthly Notices of the Royal Astronomical Society

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“…In this Letter, we report on new measurements of resonantly excited Fe XVI and Fe XVII with a synchrotron source at tenfold improved spectral resolution and millionfold lower peak photon flux than in [25], suppressing nonlinear dynamical effects [32,34,38] and undesired ion population transfers [35]. We also carry out improved large-scale calculations using three different advanced approaches [39][40][41], all showing a five-sigma departure from our experimental results.…”

mentioning

confidence: 73%

“…Nonetheless, at the high peak brilliance of the LCLS XFEL, nonlinear excitation dynamics [32,33] or nonequilibrium time evolution [34] might have affected the result of Bernitt et al [25]. An effect of resonance-induced population transfer between Fe XVI and Fe XVII ions was also postulated [35] since the Fe XVI line C (½ð2p 5 Þ 1=2 3s3d 5=2 J¼3=2 → ½2p 6 3s J¼1=2 ) appeared blended with the Fe XVII line 3D. A recent semiempirical calculation [36] reproduces the LCLS results [25] by finetuning relativistic couplings and orbital relaxation effects, but its validity has been disproved [37].…”

mentioning

confidence: 99%

“…This gives us the 3C=3D intensity ratio without having to infer a contribution of Fe XVI line C (in [25] still unresolved) from the intensity of the well-resolved Fe XVI A line. Thereby, we largely reduce systematic uncertainties and exclude the resonanceinduced population transfer mechanism [35] that may have affected the LCLS result [25].…”

mentioning

confidence: 99%

“…With modern [51][52][53]. Blue crosses: predictions [29,31,32,35,36,[54][55][56][57]. Note that the validity of theory [36] has been disputed [37].…”

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confidence: 99%

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High Resolution Photoexcitation Measurements Exacerbate the Long-Standing Fe XVII Oscillator Strength Problem

Kühn¹,

Shah²,

López‐Urrutia³

et al. 2020

Phys. Rev. Lett.

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For more than 40 years, most astrophysical observations and laboratory studies of two key soft x-ray diagnostic 2p − 3d transitions, 3C and 3D, in Fe XVII ions found oscillator strength ratios fð3CÞ=fð3DÞ disagreeing with theory, but uncertainties had precluded definitive statements on this much studied conundrum. Here, we resonantly excite these lines using synchrotron radiation at PETRA III, and reach, at a millionfold lower photon intensities, a 10 times higher spectral resolution, and 3 times smaller uncertainty than earlier work. Our final result of fð3CÞ=fð3DÞ ¼ 3.09ð8Þð6Þ supports many of the earlier clean astrophysical and laboratory observations, while departing by five sigmas from our own newest large-scale ab initio calculations, and excluding all proposed explanations, including those invoking nonlinear effects and population transfers.

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Variation of the transition energies and oscillator strengths for the 3C and 3D lines of the Ne-like ions under plasma environment

Chen

Chang

et al. 2019

J. Phys. B: At. Mol. Opt. Phys.

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We present the results of a detailed theoretical study which meets the spatial and temporal criteria of the Debye-Huckel (DH) approximation on the variation of the transition energies as well as the oscillator strengths for the 2p 5 3d 1 P 1 → 2p 6 1 S 0 (3C line) and the 2p 5 3d 3 D 1 → 2p 6 1 S 0 (3D line) transitions of the Ne-like ions subject to external plasma. Our study shows that the redshifts of the transition energy follow the general scaling behaviors similar to the ones for the simple H-like and He-like ions. Whereas the oscillator strength for the 3C line decreases, the oscillator strength for the spin-flipped 3D line increases as the strength of the outside plasma increases. As a result, their ratio is amplified subject to outside plasma environment. We further demonstrate that the plasma-induced variation between the relative strength of the 3C and 3D transitions is mainly due to the spin-dependent interactions which dictate the mixing of the 1 P 1 component in the 3 D 1 upper state of the 3D transition. In addition, we are able to find that the ratio between the relative oscillator strengths of the 3C and 3D lines in the presence of the plasma to their respective plasma-free values varies as a nearly universal function of [(Z − 9.2)DZ] −1.8 , with Z the nuclear charge and D the Debye length. The results of this study should be of great help in the modelling and diagnostic of astrophysical plasmas as well as laboratory plasmas.

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Change of the relative line strengths due to the resonance induced population transfer between Fe XVII and FeXVI ions

Cited by 9 publications

References 40 publications

The warm-hot circumgalactic medium around EAGLE-simulation galaxies and its detection prospects with X-ray and UV line absorption

The warm-hot circumgalactic medium around EAGLE-simulation galaxies and its detection prospects with X-ray and UV line absorption

High Resolution Photoexcitation Measurements Exacerbate the Long-Standing Fe XVII Oscillator Strength Problem

Variation of the transition energies and oscillator strengths for the 3C and 3D lines of the Ne-like ions under plasma environment

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