Interstellar Silicon Depletion and the Ultraviolet Extinction

Mishra, Ajay Kumar; Li, Aigen

doi:10.3847/1538-4357/aa937a

Cited by 25 publications

(19 citation statements)

References 70 publications

(124 reference statements)

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“…Let a sil and a gra respectively be the mean sizes of the silicate and graphite grains, each weighted by grain area, grain mass, or V -band extinction cross section [C ext (a, λ V )]. We also derive the "overall mean grain size" as the average of a sil and a gra , weighted by the mass fraction of each dust component in the same manner as described in §6 of Mishra & Li (2017). Our results closely resemble that of Mishra & Li (2017;see their Figures 14, 15): the area-, mass-, and C ext (a, λ V )-weighted mean grain sizes all anti-correlate with R −1 V .…”

Section: Discussionsupporting

confidence: 59%

“…We also derive the "overall mean grain size" as the average of a sil and a gra , weighted by the mass fraction of each dust component in the same manner as described in §6 of Mishra & Li (2017). Our results closely resemble that of Mishra & Li (2017;see their Figures 14, 15): the area-, mass-, and C ext (a, λ V )-weighted mean grain sizes all anti-correlate with R −1 V . This clearly shows that denser regions of larger R V values, on an average, are characterized by larger grains.…”

Section: Discussionsupporting

confidence: 59%

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Interstellar Extinction and Elemental Abundances

Zuo

Zhao

2021

ApJS

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While it is well recognized that both the Galactic interstellar extinction curves and the gas-phase abundances of dust-forming elements exhibit considerable variations from one sightline to another, as yet most of the dust extinction modeling efforts have been directed to the Galactic average extinction curve, which is obtained by averaging over many clouds of different gas and dust properties. Therefore, any details concerning the relationship between the dust properties and the interstellar environments are lost. Here we utilize the wealth of extinction and elemental abundance data obtained by space telescopes and explore the dust properties of a large number of individual sightlines. We model the observed extinction curve of each sightline and derive the abundances of the major dust-forming elements (i.e., C, O, Si, Mg and Fe) required to be tied up in dust (i.e., dust depletion). We then confront the derived dust depletions with the observed gas-phase abundances of these elements and investigate the environmental effects on the dust properties and elemental depletions. It is found that for the majority of the sightlines the interstellar oxygen atoms are fully accommodated by gas and dust and therefore there does not appear to be a "missing oxygen" problem. For those sightlines with an extinction-to-hydrogen column density A V /N H 4.8 × 10 −22 mag cm 2 H −1 there are shortages of C, Si, Mg and Fe elements for making dust to account for the observed extinction, even if the interstellar C/H, Si/H, Mg/H and Fe/H abundances are assumed to be protosolar abundances augmented by Galactic chemical evolution.

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Section: Discussionsupporting

confidence: 59%

Section: Discussionsupporting

confidence: 59%

Interstellar Extinction and Elemental Abundances

Zuo

Zhao

2021

ApJS

Self Cite

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“…From the observations of 16 Galactic sightlines, Haris et al (2016) claimed that that the silicon depletion correlates with the 2175 Å bump and the far-UV extinction rise. However, more recently Mishra & Li (2017) found that the bump strength correlates with carbon abundance instead of silicon and there is no correlation of far-UV extinction with either silicon or carbon abundance using a silicate-graphite model on a larger sample. This discrepancy could be related to the different methods adopted for determining the silicon dust depletion and usage of different interstellar abundances of silicon in the two studies.…”

Section: Introductionmentioning

confidence: 93%

“…Previously, extinction curve models suggested that small silicate grains are responsible for the far-UV rise (Mathis et al 1977;Draine & Lee 1984;Weingartner & Draine 2001;Clayton et al 2003). However, Mishra & Li (2017) fitted the observed Galactic sightlines with a silicate-graphite dust model and reported that neither silicate nor carbonaceous dust correlates with the far-UV extinction. The far-UV extinction may therefore originate from a combined effect of both small carbon and silicate grains.…”

Section: Far-uv Rise Against Dust-phase Si and Fementioning

confidence: 99%

Silicon and iron dust in gamma-ray burst host galaxy absorbers

Zafar,

Heintz,

Karakas

et al. 2019

Preprint

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Depletion studies provide a way to understand the chemical composition of interstellar dust grains. We here examine 23 gamma-ray bursts (GRB) optical afterglow spectra (spanning 0.6 z 5.0) and compare their silicon and iron dust-phase column densities with different extinction curve parameters to study the composition of the interstellar dust grains in these high-redshift GRB host galaxies. The majority of our sample (87%) show featureless extinction curves and only vary in shape. We observe strong correlations (with > 96% significance) between the total-to-selective extinction, R V , and the dust-phase column densities of Si and Fe. Since a large fraction of interstellar iron is locked in silicate grains, this indicates that high Si and Fe depletion leads to an increase in the fraction of large silicate grains and vice versa. This suggests that silicates play a vital role to induce the entire extinction at any wavelength. On the other hand, the far-UV extinction is usually attributed to the presence of small silicates. However, we find no trend between the far-UV parameter of the extinction curve, c 4 , and the abundance of Si and Fe in the dust phase. We, therefore, propose that the far-UV extinction could be a combined effect of small (probably nanoparticles) dust grains from various species.

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“…The discrepancy between the lower estimates of total carbon abundances and dust models is known as the "carbon crisis" (Kim & Martin 1996). However, the models based on UV extinction curves only indirectly estimate the amount of carbon in the solid phase (Mishra & Li 2017). A direct spectroscopic measurement is desirable.…”

Section: Introductionmentioning

confidence: 99%

Aliphatic hydrocarbon content of interstellar dust

Günay

Schmidt

Burton

et al. 2018

Monthly Notices of the Royal Astronomical Society

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In the interstellar medium, carbon is distributed between the gas and solid phases. However, while about half of the expected carbon abundance can be accounted for in the gas phase, there is considerable uncertainty as to the amount incorporated in interstellar dust.The aliphatic component of the carbonaceous dust is of particular interest because it produces a significant 3.4 µm absorption feature when viewed against a background radiation source. The optical depth of the 3.4 µm absorption feature is related to the number of aliphatic carbon C-H bonds along the line of sight. It is possible to estimate the column density of carbon locked up in the aliphatic hydrocarbon component of interstellar dust from quantitative analysis of the 3.4 µm interstellar absorption feature providing that the absorption coefficient of aliphatic hydrocarbons incorporated in the interstellar dust is known.We generated laboratory analogues of interstellar dust by experimentally mimicking interstellar/circumstellar conditions. The resultant spectra of these dust analogues closely match those from astronomical observations. The measurements of the absorption coefficient of aliphatic hydrocarbons incorporated in the analogues were carried out by a procedure which combined FTIR and 13 C NMR spectroscopies. The absorption coefficients obtained for both interstellar analogues were found to be in close agreement (4.76(8) × 10 −18 cm group −1 and 4.69(14) × 10 −18 cm group −1 ), less than half those obtained in studies using small aliphatic molecules. The results thus obtained permit direct calibration of the astronomical observations, providing rigorous estimates of the amount of aliphatic carbon in the interstellar medium.

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Interstellar Silicon Depletion and the Ultraviolet Extinction

Cited by 25 publications

References 70 publications

Interstellar Extinction and Elemental Abundances

Interstellar Extinction and Elemental Abundances

Silicon and iron dust in gamma-ray burst host galaxy absorbers

Aliphatic hydrocarbon content of interstellar dust

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