scholarly journals Measurements of Interstellar Extinction

1989 ◽  
Vol 135 ◽  
pp. 3-21 ◽  
Author(s):  
D. Massa ◽  
Blair D. Savage
Keyword(s):  
Interstellar Extinction ◽  
Extinction Curve ◽  
Central Position ◽  
Average Width ◽  
Near Ir ◽  
Linear Rise ◽  
Diffuse Cloud ◽  
Shape Changes ◽  
Cloud Medium ◽  
Made In

The results of interstellar extinction measurements from the near IR to the far-UV are reviewed. The average interstellar extinction curve for the diffuse cloud medium exhibits a nearly linear rise (in 1/λ) from 1 μm−1 to the 2.25 μm−1 “knee” in extinction where the slope changes. In the UV there is a pronounced extinction bump near 4.6 μm−1 (2175 å) followed by a broad minimum and a steep rise in extinction to the shortest wavelengths for which measurements exist. For wavelengths shortward of about 5500 å, the interstellar extinction curve exhibits considerable variation in shape from one sight line to another. In addition to strength variations, the width (FWHM) of the 2175 å extinction bump has been observed to vary by more than a factor of two from 360 to 770 å with the average width being 480 å. In contrast, the central position of the feature only varies from 2110 å to 2195 å with the average central position being 2175 å. The most extreme variations in extinction are found at far-UV wavelengths where E(λ – V)/E(B – V) has been found to range from 3 to 12.5 at 1250 A. In the last few years significant progress has been made in determining various empirical relationships among extinction parameters in the different wavelength regimes and in determining how extinction curve shape changes are influenced by the interstellar environment in which the dust resides. Those relationships are discussed.

scholarly journals Interstellar Extinction in 20 Open Star Clusters

2017 ◽  
Vol 34 ◽  
Author(s):  
Geeta Rangwal ◽  
R. K. S. Yadav ◽  
Alok K. Durgapal ◽  
D. Bisht
Keyword(s):  
Spatial Variation ◽  
Star Clusters ◽  
Interstellar Extinction ◽  
Open Star Clusters ◽  
Circumstellar Material ◽  
Open Star ◽  
Near Ir ◽  
Spectral Class ◽  
Colour Excess ◽  
The Difference

AbstractThe interstellar extinction law in 20 open star clusters namely, Berkeley 7, Collinder 69, Hogg 10, NGC 2362, Czernik 43, NGC 6530, NGC 6871, Bochum 10, Haffner 18, IC 4996, NGC 2384, NGC 6193, NGC 6618, NGC 7160, Collinder 232, Haffner 19, NGC 2401, NGC 6231, NGC 6823, and NGC 7380 have been studied in the optical and near-IR wavelength ranges. The difference between maximum and minimum values of E(B − V) indicates the presence of non-uniform extinction in all the clusters except Collinder 69, NGC 2362, and NGC 2384. The colour excess ratios are consistent with a normal extinction law for the clusters NGC 6823, Haffner 18, Haffner 19, NGC 7160, NGC 6193, NGC 2401, NGC 2384, NGC 6871, NGC 7380, Berkeley 7, Collinder 69, and IC 4996. We have found that the differential colour-excess ΔE(B − V), which may be due to the occurrence of dust and gas inside the clusters, decreases with the age of the clusters. A spatial variation of colour excess is found in NGC 6193 in the sense that it decreases from east to west in the cluster region. For the clusters Berkeley 7, NGC 7380, and NGC 6871, a dependence of colour excess E(B − V) with spectral class and luminosity is observed. Eight stars in Collinder 232, four stars in NGC 6530, and one star in NGC 6231 have excess flux in near-IR. This indicates that these stars may have circumstellar material around them.

Contribution of Pahs to the Interstellar Extinction Curve

1992 ◽  
pp. 21-22 ◽  
Author(s):  
C. Joblin ◽  
A. Leger ◽  
P. Martin ◽  
D. Defourneau
Keyword(s):  
Interstellar Extinction ◽  
Extinction Curve

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 Martyrs made in the sky: the Zénith balloon tragedy and the construction of the French Third Republic's first scientific heroes

2019 ◽  
Vol 74 (3) ◽  
pp. 365-386
Author(s):  
Patrick Luiz Sullivan De Oliveira
Keyword(s):  
Twentieth Century ◽  
High Altitude ◽  
Scientific Community ◽  
Central Position ◽  
Practical Applications ◽  
The Third ◽  
Early Twentieth Century ◽  
Claude Bernard ◽  
Made In

Following the balloon's invention in 1783, the French greeted the technology with enthusiasm, speculating extensively about its potential scientific and practical applications. However, the lack of progress in navigating against the winds discredited ballooning, and in the following decades it became the domain of spectacular forms of entertainment and of swindlers trying to defraud public subscriptions. All of this changed after the 1870–1871 Franco-Prussian War, during which balloons were used to breach the siege of Paris. This essay explores how the aeronautical community, led by the recently established Société Française de Navigation Aérienne, mobilized the memory of the war to transform the balloon into a symbol of a heroic republican science. Paramount in that process was the Zénith 's 1875 high-altitude ascent that killed two aeronauts—Joseph Crocé-Spinelli and Théodore Sivel. The tragedy reverberated beyond France's scientific community, and through popular acclaim the two aeronauts became the Third Republic's first scientific martyrs, anticipating the eventual apotheoses of figures like Claude Bernard and Louis Pasteur. The ballooning revival in the last third of the century helped strengthen the association between France and aeronautics, thus setting the stage for the country to acquire a central position in the field by the early twentieth century.

The ultraviolet interstellar extinction curve in the Pleiades

1981 ◽  
Vol 244 ◽  
pp. 199 ◽  
Author(s):  
A. N. Witt ◽  
R. C. Bohlin ◽  
T. P. Stecher
Keyword(s):  
Interstellar Extinction ◽  
Extinction Curve

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 Space Distribution of Planetary Nebulae

1968 ◽  
Vol 34 ◽  
pp. 44-50 ◽  
Author(s):  
J.H. Cahn
Keyword(s):  
Computer Program ◽  
White Dwarf ◽  
Local Density ◽  
Planetary Nebulae ◽  
Interstellar Extinction ◽  
Space Distribution ◽  
Using Data ◽  
Dust Distribution ◽  
Made In

A punched-card catalogue of planetary nebulae has been prepared, using data extracted from all existing catalogues. A computer program calculates distances and radii using the method of Shklovsky, in which all nebulae are assumed to have the same ionized mass, and allowance for interstellar extinction is made assuming a continuous galactic-dust distribution. The assumption made in Shklovsky's method, that the nebulae are optically thin, is considered to be satisfied if the calculated radii lie within a certain well-defined interval. The reddening constants obtained are in satisfactory statistical agreement with constants determined by other methods. The local density of planetary nebulae is in agreement with estimates of local white-dwarf densities.

scholarly journals How much graphene in space?

2019 ◽  
Vol 490 (3) ◽  
pp. 3875-3881 ◽  
Author(s):  
Qi Li ◽  
Aigen Li ◽  
B W Jiang
Keyword(s):  
Energy Range ◽  
Interband Transition ◽  
Interstellar Extinction ◽  
Extinction Curve ◽  
Previous Estimate ◽  
Upper Limit ◽  
Vibrational Bands ◽  
Ir Emission ◽  
Electron Energy Loss ◽  
Planar Graphene

ABSTRACT The possible presence of graphene in the interstellar medium (ISM) is examined by comparing the interstellar extinction curve with the ultraviolet absorption of graphene calculated from its dielectric functions experimentally obtained with the electron energy loss spectroscopy (EELS) method. Based on the absence in the interstellar extinction curve of the $\sim \! 2755\, {\rm \mathring{\rm A} }$ π–π* electronic interband transition of graphene, we place an upper limit of $\sim \! 20\, {\rm ppm}$ of C/H on the interstellar graphene abundance, exceeding the previous estimate by a factor of $\sim \,$3 which made use of the dielectric functions measured with the spectroscopic ellipsometry (SE) method. Compared with the SE method which measures graphene in air (and hence its surface is contaminated) in a limited energy range of $\sim \,$0.7–5 $\, {\rm eV}$, the EELS probes a much wider energy range of $\sim \,$0–50 $\, {\rm eV}$ and is free of contamination. The fact that the EELS dielectric functions are substantially smaller than that of SE naturally explains why a higher upper limit on the graphene abundance is derived with EELS. Inspired by the possible detection of C24, a planar graphene sheet, in several Galactic and extragalactic planetary nebulae, we also examine the possible presence of C24 in the diffuse ISM by comparing the model IR emission of C24 with the observed IR emission of the Galactic cirrus and the diffuse ISM towards l = 44°20′ and b = −0°20′. An upper limit of $\sim \!20\, {\rm ppm}$ on C24 is also derived from the absence of the characteristic vibrational bands of C24 at $\sim \,$6.6, 9.8, and 20 $\, {\rm \mu m}$ in the observed IR emission.

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.

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