Missing Fe: hydrogenated iron nanoparticles

Bilalbegović, Goranka; Maksimović, Aleksandar; Mohaček-Grošev, Vlasta

doi:10.1093/mnrasl/slw226

Cited by 13 publications

(7 citation statements)

References 81 publications

(92 reference statements)

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“…For example, from experiments in microgravity, Kimura et al (2017) concluded that the probability of the formation of pure iron grains should be very low and that, consequently, iron should be bound in iron compounds or accreted as impurities on other grains in the ISM. Another hypothesis was pursued by Bilalbegović et al (2016) who calculated infrared absorption spectra of hydrogenated iron particles. From a variety of astronomical observations and related astrophysical modeling, several groups inferred that a large fraction of the iron in the ISM could be incorporated as inclusions in silicate grains (Zhukovska et al 2018;Westphal et al 2019;Zafar et al 2019).…”

Section: Comparison With Other Forms Of Ironmentioning

confidence: 99%

Near L-edge Single and Multiple Photoionization of Doubly Charged Iron Ions

Schippers

Martins

Beerwerth³

et al. 2021

ApJ

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Using the photon-ion merged-beams technique at a synchrotron light source, we have measured relative cross sections for single and up to five-fold photoionization of Fe 2+ ions in the energy range of 690-920eV. This range contains thresholds and resonances associated with ionization and excitation of 2p and 2s electrons. Calculations were performed to simulate the total absorption spectra. The theoretical results show very good agreement with the experimental data, if overall energy shifts of up to 2.5eV are applied to the calculated resonance positions and assumptions are made about the initial experimental population of the various levels of the Fe 2+ ([Ar]3d 6 ) ground configuration. Furthermore, we performed extensive calculations of the Auger cascades that result when an electron is removed from the 2p subshell of Fe 2+ . These computations lead to a better agreement with the measured product-charge-state distributions as compared to earlier work. We conclude that the L-shell absorption features of low-charged iron ions are useful for identifying gas-phase iron in the interstellar medium and for discriminating against the various forms of condensed-phase iron bound to composite interstellar dust grains.Unified Astronomy Thesaurus concepts: Interstellar atomic gas (833); Interstellar clouds (834); Interstellar medium (847); Interstellar absorption (831); Line intensities (2084); Atomic spectroscopy (2099); Line positions (2085); X-ray astronomy (1810); Laboratory astrophysics (2004)

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Section: Comparison With Other Forms Of Ironmentioning

confidence: 99%

Near L-edge Single and Multiple Photoionization of Doubly Charged Iron Ions

Schippers

Martins

Beerwerth³

et al. 2021

ApJ

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Section: Silicate Cationsmentioning

confidence: 99%

Magnesium and silicon in interstellar dust: X-ray overview

Rogantini

Costantini

Zeegers

et al. 2020

A&A

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Context. The dense Galactic environment is a large reservoir of interstellar dust. Therefore, this region represents a perfect laboratory to study the properties of cosmic dust grains. X-rays are the most direct way to detect the interaction of light with dust present in these dense environments. Aims. The interaction between the radiation and the interstellar matter imprints specific absorption features on the X-ray spectrum. We study them with the aim of defining the chemical composition, the crystallinity, and structure of the dust grains that populate the inner regions of the Galaxy. Methods. We investigated the magnesium and the silicon K-edges detected in the Chandra /HETG spectra of eight bright X-ray binaries, distributed in the neighbourhood of the Galactic centre. We modelled the two spectral features using accurate extinction cross-sections of silicates, which we measured at the synchrotron facility Soleil, France. Results. Near the Galactic centre, magnesium and silicon show abundances similar to the solar ones and they are highly depleted from the gas phase (δMg > 0.90 and δSi > 0.96). We find that amorphous olivine with a composition of MgFeSiO4 is the most representative compound along all lines of sight according to our fits. The contribution of Mg-rich silicates and quartz is low (less than 10%). On average we observe a percentage of crystalline dust equal to 11%. For the extragalactic source LMC X-1, we find a preference for forsterite, a magnesium-rich olivine. Along this line of sight we also observe an under-abundance of silicon ASi∕ALMC = 0.5 ± 0.2.

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“…From the fit of the Mg and Si edges and the related ζ Mg values, we can extrapolate that a large fraction of iron is expected to be in interstellar silicates, at least for the considered lines of sight. The solid form of the interstellar iron is still highly debated and among the forms of iron considered in literature there are oxides (Draine & Hensley 2013), metallic Fe (Westphal et al 2019), inclusions of Fe and FeS in silicate grains, free-flying iron particles (Zhukovska et al 2018) and hydrogenated iron nanoparticles (Bilalbegović et al 2017). Future instruments, such as the coming X-ray Imaging and Spectroscopy Mission (XRISM, Tashiro et al 2018) and the future Athena X-ray mission (Nandra et al 2013;Barret et al 2016), will allow to simultaneously study the Mg and Si K-edges with the Fe K-edge, especially for high column-density lines of sight (Rogantini et al 2018).…”

Section: Silicate Cationsmentioning

confidence: 99%

Magnesium and silicon in interstellar dust: an X-ray overview

Rogantini,

Costantini,

Zeegers

et al. 2020

Preprint

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Context. The dense Galactic environment is a large reservoir of interstellar dust. Therefore, this region represents a perfect laboratory to study the properties of the cosmic dust grains. X-rays are the most direct way to detect the interaction of light with dust present in these dense environments. Aims. The interaction between the radiation and the interstellar matter imprints specific absorption features in the X-ray spectrum. We study them with the aim of defining the chemical composition, the crystallinity and structure of the dust grains which populate the inner regions of the Galaxy. Methods. We investigate the magnesium and the silicon K-edges detected in the Chandra/HETG spectra of eight bright X-ray binaries, distributed in the neighbourhood of the Galactic centre. We model the two spectral features using accurate extinction cross sections of silicates, that we have measured at the synchrotron facility Soleil, France. Results. Near the Galactic centre magnesium and silicon show abundances similar to the solar ones and they are highly depleted from the gas phase (δ Mg > 0.90 and δ Si > 0.96). We find that amorphous olivine with a composition of MgFeSiO 4 is the most representative compound along all lines of sight according to our fits. The contribution of Mg-rich silicates and quartz is low (less than 10%). On average we observe a percentage of crystalline dust equal to 11%. For the extragalactic source LMC X-1, we find a preference for forsterite, a magnesium-rich olivine. Along this line of sight we also observe an underabundance of silicon A Si /A LMC = 0.5 ± 0.2.

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Missing Fe: hydrogenated iron nanoparticles

Cited by 13 publications

References 81 publications

Near L-edge Single and Multiple Photoionization of Doubly Charged Iron Ions

Near L-edge Single and Multiple Photoionization of Doubly Charged Iron Ions

Magnesium and silicon in interstellar dust: X-ray overview

Magnesium and silicon in interstellar dust: an X-ray overview

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