scholarly journals Probing the missing link between the diffuse interstellar bands and the total-to-selective extinction ratio $R_V\,\!-\!$ I. Extinction versus reddening

2019 ◽  
Vol 489 (1) ◽  
pp. 708-713 ◽  
Author(s):  
Kaijun Li ◽  
Aigen Li ◽  
F Y Xiang
Keyword(s):  
Extinction Ratio ◽  
Interstellar Extinction ◽  
Extinction Curve ◽  
Interstellar Clouds ◽  
Diffuse Interstellar Bands ◽  
Hydrogen Column Density ◽  
Wide Range ◽  
Chemical Conditions ◽  
Physical And Chemical ◽  
Selective Extinction

ABSTRACT The carriers of the still (mostly) unidentified diffuse interstellar bands (DIBs) have been a long-standing mystery ever since their first discovery exactly 100 yr ago. In recent years, the ubiquitous detection of a large number of DIBs in a wide range of Galactic and extragalactic environments has led to renewed interest in connecting the occurrence and properties of DIBs to the physical and chemical conditions of the interstellar clouds, with particular attention paid to whether the DIB strength is related to the shape of the interstellar extinction curve. To shed light on the nature and origin of the DIB carriers, we investigate the relation between the DIB strength and RV, the total-to-selective extinction ratio, which characterizes how the extinction varies with wavelength (i.e. the shape of the extinction curve). We find that the DIB strength and RV are not related if we represent the strength of a DIB by its reddening-normalized equivalent width (EW), in contrast to the earlier finding of an anticorrelation in which the DIB strength is measured by the extinction-normalized EW. This raises a fundamental question about the appropriate normalization for the DIB EW. We argue that the hydrogen column density is a more appropriate normalization than extinction and reddening.

scholarly journals The interstellar extinction curve from 4000 Å to 6500 Å

1970 ◽  
Vol 36 ◽  
pp. 52-56
Author(s):  
G. A. H. Walker ◽  
J. B. Hutchings ◽  
P. F. Younger
Keyword(s):  
Interstellar Extinction ◽  
Absorption Peak ◽  
Extinction Curve ◽  
Linear Section ◽  
Broad Absorption ◽  
Diffuse Interstellar Bands

Interstellar extinction curves (mext vs. 1/λ) of 20 Å resolution have been obtained at the DAO from photoelectric scanner observations in the range 4000 Å to 5000 Å for five stars, and of 50 Å resolution for four stars in the range 4000 Å to 6500 Å from Willstrop's photoelectric data. There is a closely linear section between 4900 Å and 5800 Å for all of the curves. There are changes of gradient or discontinuities associated with the broadest diffuse interstellar bands at 6180 Å, 4882 Å, 4761 Å and 4430 Å. There is a marked discontinuity near 5800 Å and for some stars a broad absorption near 4200 Å. The 4430 Å band lies between two unequal wings of anomalously low extinction (one of which has been detected at Edinburgh). The irregularities vary from star to star, and those in the neighbourhood of the 4430 Å band seem to have the same form as those in the region of the absorption peak at 2200 Å

scholarly journals Interstellar Extinction and Elemental Abundances: Individual Sight Lines

2021 ◽  
Vol 257 (2) ◽  
pp. 63
Author(s):  
Wenbo Zuo ◽  
Aigen Li ◽  
Gang Zhao
Keyword(s):  
Gas Phase ◽  
Interstellar Extinction ◽  
Elemental Abundance ◽  
Extinction Curve ◽  
Galactic Chemical Evolution ◽  
Space Telescopes ◽  
Dust Extinction ◽  
Elemental Abundances ◽  
Hydrogen Column Density ◽  
The Relationship

Abstract 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 sight line 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 sight lines. We model the observed extinction curve of each sight line 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 sight lines 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 sight lines with an extinction-to-hydrogen column density A V /N H ≳ 4.8 × 10−22 mag cm2 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.

scholarly journals Composition and Ligand Microstructure of Arsenopyrite from Gold Ore Deposits of the Yenisei Ridge (Eastern Siberia, Russia)

Minerals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 737 ◽  
Author(s):  
Anatoly M. Sazonov ◽  
Sergey A. Silyanov ◽  
Oleg A. Bayukov ◽  
Yuriy V. Knyazev ◽  
Yelena A. Zvyagina ◽  
...  
Keyword(s):  
High Spin ◽  
Local Symmetry ◽  
Gold Deposits ◽  
Ore Deposits ◽  
Yenisei Ridge ◽  
Eastern Siberia ◽  
Wide Range ◽  
Mineral Structure ◽  
Chemical Conditions ◽  
Physical And Chemical

The Mössbauer spectroscopy method was used to study the ligand microstructure of natural arsenopyrite (31 specimens) from the ores of the major gold deposits of the Yenisei Ridge (Eastern Siberia, Russia). Arsenopyrite and native gold are paragenetic minerals in the ore; meanwhile, arsenopyrite is frequently a gold carrier. We detected iron positions with variable distribution of sulfur and arsenic anions at the vertexes of the coordination octahedron {6S}, {5S1As}, {4S2As}, {3S3As}, {2S4As}, {1S5As}, {6As} in the mineral structure. Iron atoms with reduced local symmetry in tetrahedral cavities, as well as iron in the high-spin condition with a high local symmetry of the first coordination sphere, were identified. The configuration {3S3As} typical for the stoichiometric arsenopyrite is the most occupied. The occupation degree of other configurations is not subordinated to the statistic distribution and varies within a wide range. The presence of configurations {6S}, {3S3As}, {6As} and their variable occupation degree indicate that natural arsenopyrites are solid pyrite {6S}, arsenopyrite {3S3As}, and loellingite {6As} solutions, with the thermodynamic preference to the formation of configurations in the arsenopyrite–pyrite–loellingite order. It is assumed that in the variations as part of the coordination octahedron, the iron output to the tetrahedral positions and the presence of high-spin Fe cations depend on the physical and chemical conditions of the mineral formation. It was identified that the increased gold concentrations are typical for arsenopyrites with an elevated content of sulfur or arsenic and correlate with the increase of the occupation degree of configurations {5S1As}, {4S2As}, {1S5As}, reduction of the share of {3S3As}, and the amount of iron in tetrahedral cavities.

The Interaction of Borosilicate Glass and Grawodiorite at 100°C, 50 Mpa: Implications For Models Of Radionuclide Release

1981 ◽  
Vol 11 ◽  
Author(s):  
David Savage ◽  
Jane E. RObbins
Keyword(s):  
Near Field ◽  
Quantitative Prediction ◽  
Wide Range ◽  
Modelling Studies ◽  
Chief Factors ◽  
Chemical Conditions ◽  
C 50 ◽  
Radionuclide Release ◽  
Physical And Chemical ◽  
Fluid Interaction

An essential component of any assessment of HLRW geological disposal options is the quantitative prediction of radionuclide release rates from the near-field over time spans of the order of 103-106 years. Fundamental to this assessment is the investigation of the interaction of potential wasteforms with groundwater under repository conditions of temperature, pressure, and groundwater flow-rate. Consequently, many studies world-wide have been initiated to examine the kinetics of wasteform dissolution over a wide range of physical and chemical conditions. Although these studies have provided a considerable amount of invaluable data on wasteform-fluid interactions, they have tended to focus on breakdown of the wasteform itself, and not on the fate of released waste components in the nearfield. For example, effects of saturation of species in solution, precipitation of secondary minerals or amorphous gels, and the effect of host rock chemistry on the products (solid and fluid) of waste-fluid interaction have largely been ignored or even specifically excluded in laboratory experiments. This is despite growing evidence from source term modelling studies which suggest that the above processes may well be the chief factors in governing rates of radionuclide release from the near-field, bearing in mind the limited availability of ground

Interstellar Extinction from Large Surveys

2003 ◽  
Vol 12 (4) ◽  
Author(s):  
O. Yu. Malkov
Keyword(s):  
Survey Data ◽  
Extinction Ratio ◽  
Interstellar Extinction ◽  
Galactic Latitude ◽  
Virtual Observatory ◽  
Multicolor Photometry ◽  
Selective Extinction

AbstractUnder some assumptions, information on interstellar extinction may be obtained from modern large photometric survey data. Virtual Observatory facilities allow users to make a fast and correct cross-identification of objects from various surveys. This process yields multicolor photometry data for registered objects and makes it possible to estimate color excesses and, with a few exceptions for some areas with high total-to-selective extinction ratio, calculate interstellar extinction. A 3D extinction map then can be constructed for almost the whole sky. The method is applied to an area with the low Galactic latitude, and the results are discussed in the present paper.

scholarly journals On carbon nanotubes in the interstellar medium

2020 ◽  
Vol 493 (2) ◽  
pp. 3054-3059
Author(s):  
Qi Li ◽  
Aigen Li ◽  
B W Jiang ◽  
Tao Chen
Keyword(s):  
Carbon Nanotubes ◽  
Interstellar Medium ◽  
Interstellar Extinction ◽  
Extinction Curve ◽  
Interstellar Space ◽  
Absorption Bands ◽  
Carbon Allotrope ◽  
Wide Range ◽  
Polycyclic Aromatic ◽  
The Universe

ABSTRACT Since their discovery in 1991, carbon nanotubes (CNTs) – a novel one-dimensional carbon allotrope – have attracted considerable interest worldwide because of their potential technological applications such as electric and optical devices. In the astrophysical context, CNTs may be present in the interstellar space since many of the other allotropes of carbon (e.g. amorphous carbon, fullerenes, nanodiamonds, graphite, polycyclic aromatic hydrocarbons, and possibly graphene as well) are known to be widespread in the Universe, as revealed by pre-solar grains in carbonaceous primitive meteorites and/or by their fingerprint spectral features in astronomical spectra. In addition, there are also experimental and theoretical pathways to the formation of CNTs in the interstellar medium (ISM). In this work, we examine their possible presence in the ISM by comparing the observed interstellar extinction curve with the ultraviolet/optical absorption spectra experimentally obtained for single-walled CNTs of a wide range of diameters and chiralities. Based on the absence in the interstellar extinction curve of the ${\sim}$4.5 and 5.25 ${\rm eV} \ \pi$-plasmon absorption bands that are pronounced in the experimental spectra of CNTs, we place an upper limit of ${\sim}10\, {\rm ppm}$ of C/H (i.e. ${\sim}$4 per cent of the total interstellar C) on the interstellar CNT abundance.

scholarly journals Grains in Diffuse Clouds: Carbon-Coated Silicate Cores

1989 ◽  
Vol 135 ◽  
pp. 367-373
Author(s):  
David A. Williams
Keyword(s):  
Interstellar Medium ◽  
Amorphous Carbon ◽  
Laboratory Data ◽  
Interstellar Extinction ◽  
Extinction Curve ◽  
Total Carbon ◽  
Small Radius ◽  
Carbon Coatings ◽  
Wide Range ◽  
Diffuse Clouds

A new model of interstellar grains is proposed in which grains in diffuse clouds consist of small (radius ≲ 10nm) and large asymmetric (0.05μm – 0.25μm) silicate cores thinly coated with mantles of amorphous carbon (thickness ≲ 5nm). This model can account successfully for many of the observed properties of interstellar dust and gives a simple interpretation of the interstellar extinction curve. The extinction bump at 220nm is attributed to absorption by finely divided silicates, as indicated by laboratory data. The large silicates provide a “grey” background extinction through the visual and UV, but the bulk of the extinction in this region is attributed, on the basis of laboratory data, to the amorphous carbon coatings. The average interstellar carbon depletion required in this model is about 50%.Wide variations in the observed interstellar extinction along different lines of sight are well known. These variations have a natural explanation in this model in terms of two parameters: the thickness of the carbon coatings, and the proportion of graphitic to diamond-like structure within the amorphous carbon. The underlying silicate cores are generally unchanged in these variations. The average interstellar extinction curve requires roughly equal proportions of graphitic and diamond-like forms of amorphous carbon. A higher graphitic fraction produces more visual extinction and a higher diamond-like fraction produces more far UV extinction. Varying both the proportions, and the total carbon content encompasses a wide range of extinction curve shapes.Amorphous carbon deposited at low temperature is generally diamond-like. Temperature excursions in the material reduce the hydrogen content and enhance the graphitic nature of the material. In the interstellar medium, this process has a time scale ≳ 106 yr. Carbon coatings are therefore expected to be deposited in the interstellar medium in diamond-like form and to be slowly converted to graphitelike. The growth of carbon mantles will be reversed by intermittent shocks Thus, interstellar space should contain grains with a range of thicknesses of carbon coatings, and compositions between graphitic and diamond-like.The chemical and physical properties of amorphous carbon have been the subject of intensive laboratory study. These properties enable an understanding of a variety of observations of dust (especially in the IR) and lead to a number of predictions which are described in this paper.

scholarly journals The Transition from Diffuse to Dense Clouds

1992 ◽  
Vol 45 (4) ◽  
pp. 543 ◽  
Author(s):  
Theodore P Snow
Keyword(s):  
Gas Phase ◽  
Open Cluster ◽  
Dust Particles ◽  
Interstellar Clouds ◽  
Dark Clouds ◽  
Diffuse Interstellar Bands ◽  
Cloud Characteristics ◽  
Wide Range ◽  
Diffuse Clouds ◽  
The Impact

Optical and ultraviolet spectroscopy have shown that diffuse interstellar clouds can have a wide range of properties, with especially large variations in the nature of the UV extinction curve and the abundances of molecular species. More subtle variations are found in the properties of the diffuse interstellar bands, and there have been suggestions that elemental depletions from the gas phase into solid dust particles also vary significantly. It is the purpose of this paper to review studies of the relatively diffuse interstellar clouds where these variations occur, and to explore the possible relationship between dust properties, as indicated by UV extinction, and other cloud characteristics. The focus is on relatively dense diffuse clouds, which may be viewed as transitional or intermediate between ordinary diffuse clouds and dark clouds, because in principle the greatest amount of information is available for the intermediate clouds, and because they serve as indicators of processes that may occur in the denser molecular clouds. The paper begins with a brief review of some results from the literature on transitional or intermediate clouds, and then provides a summary of some recent results on one particular cloud, in front of the star BD+31 �643, in the small open cluster IC348, which is part of the Perseus II complex of dark clouds and OB associations. The paper concludes with some tentative speculations about the possible status of the transitional clouds, along with a brief mention of the impact of upcoming instrumental developments on research in this area.

The diffuse interstellar bands III: The situation in 1966

1967 ◽  
Vol 31 ◽  
pp. 85-89 ◽  
Author(s):  
G. H. Herbig
Keyword(s):  
Strong Correlation ◽  
Line Strength ◽  
Interstellar Extinction ◽  
Polyatomic Molecules ◽  
Solid Particles ◽  
Extinction Curve ◽  
Negative Ion ◽  
Diffuse Interstellar Bands ◽  
Ionization Limit ◽  
The Continuum

Several possible identifications for the diffuse interstellar lines are reviewed. The strong correlation of diffuse-line strength and of interstellar extinction in the continuum, as well as the break in the extinction curve close to the wavelength of the strongest diffuse line (4430 Å), indicates that the absorber is closely associated with the solid particles. Possibly a molecule frozen on or in the grains may be responsible. Other possibilities considered include a negative ion with 2.8 eV as ionization limit, and free polyatomic molecules.

scholarly journals Diffuse Interstellar Bands: Families and Correlations

2013 ◽  
Vol 9 (S297) ◽  
pp. 23-33 ◽  
Author(s):  
J. Krełowski
Keyword(s):  
Molecular Species ◽  
Interstellar Extinction ◽  
Dust Particles ◽  
Physical Parameters ◽  
Strength Ratio ◽  
Interstellar Clouds ◽  
Molecular Features ◽  
Diffuse Interstellar Bands ◽  
Nearby Stars ◽  
Mutual Relations

AbstractThe term “families of diffuse bands” (DIBs) appeared in 1986/87 when my collaborators: Gordon A.H. Walker, Bengt E. Westerlund and I found that the strength ratio of the major DIBs 5780 and 5797 is heavily variable. We proved that at the same E(B-V) the DIB intensities may vary by as much as a factor of three or more. A similar result was published by Karl Josafatsson and Ted Snow soon after. A decade later, we proved (with Chris Sneden) that certain DIB strength ratios seem to be related to intensities of the known features of simple molecular species; this led to the introduction of the so called σ and ζ type interstellar clouds. The former are characterized by very weak molecular features (but broad DIBs – very strong) while the latter by rather strong bands of simple radicals and weak broad DIBs. Currently we face a bunch of questions: are the DIB intensities related to those of certain molecular species, e.g. C2 as suggested by Lew Hobbs' and Ted Snow's group? Do the DIB profiles, found to be complex by Peter Sarre, depend on e.g. the rotational temperatures of simple, linear carbon species? Do the DIB profiles depend on the irradiation of interstellar clouds by nearby stars? The relative DIB strengths as well as those of the simple radicals seem to be related to the shapes of interstellar extinction curves. We thus face three players in the interstellar translucent clouds: dust particles, simple radicals and the DIB carriers. Apparently, their mutual relations depend on local physical parameters of intervening clouds; these relations are not clear yet.

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