Interstellar Extinction in the Galaxy.

1965 ◽  
Vol 141 ◽  
pp. 923 ◽  
Author(s):  
Harold L. Johnson
Keyword(s):  
Interstellar Extinction ◽  
The Galaxy

scholarly journals Analysis of Interstellar Extinction towards the Hypergiant Cyg OB2 No. 12

2016 ◽  
Vol 25 (1) ◽  
Author(s):  
O. V. Maryeva ◽  
E. L. Chentsov ◽  
V. P. Goranskij ◽  
S. V. Karpov
Keyword(s):  
Interstellar Extinction ◽  
Stellar Association ◽  
The Galaxy ◽  
The Mean

AbstractThe Cyg OB2 stellar association hosts an entire zoo of unique objects, and among them – an enigmatic star Cyg OB2 No. 12 (Schulte 12, MT 304). MT 304 is enigmatic not only due to its highest luminosity (according to various estimates, it is one of the brightest stars in the Galaxy), but also because its reddening is anomalously large, greater than the mean reddening in the association. To explain the nature of anomalous reddening (

A discussion on infared astronomy - Expected infrared spectra of gaseous nebulae

1969 ◽  
Vol 264 (1150) ◽  
pp. 241-247 ◽  
Keyword(s):  
Infrared Spectra ◽  
Galactic Plane ◽  
Interstellar Extinction ◽  
Mount Everest ◽  
Gaseous Nebulae ◽  
The Galaxy ◽  
The Mean ◽  
Spiral Arm

If we are asked why we want to use the infrared to observe gaseous nebulae, we might reply with George Mallory, who was asked why he wanted to climb Mount Everest, ‘Because its there’. More specifically, one reason is the very great space penetration possible in the infrared. Diffuse nebulae characteristically are close to the galactic plane, and interstellar extinction therefore prevents the observation of distant objects. At MATHS FORMULA the mean range to which diffuse nebulae can easily be observed is about 1500 parsecs (pc), while many of these nebulae are so reddened as to be nearly unobservable at Hβ. It is for this reason that at present the observation of diffuse nebulae is almost entirely limited to our own spiral arm and its immediate neighbours. However, because of the decrease of interstellar extinction to longer wavelengths, at 1 μm the range of observation would be about 3000 pc; at 2 μm about 10 000 pc, comparable with the distance to the centre of the Galaxy; and at 10μm, about 100 000 pc, far larger than the diameter of the Galaxy. (The form of the interstellar reddening curve is from Whitford 1958.)

A Discussion on astronomy in the ultraviolet - The Celescope survey and the galactic distribution of interstellar absorption

1975 ◽  
Vol 279 (1289) ◽  
pp. 345-354 ◽  
Keyword(s):  
Interstellar Dust ◽  
Interstellar Extinction ◽  
Astronomical Observatory ◽  
Digital Television ◽  
National Observatory ◽  
Interstellar Absorption ◽  
The Galaxy ◽  
Galactic Distribution

The Celescope experiment consisted of four 31 cm aperture telescopes equipped with digital television photometers, installed in the Orbiting Astronomical Observatory, launched 7 December 1968. We used this instrument to conduct a survey in four ultraviolet colours: U l (2100-3200 A), U2 (1550—3200 A), U3 (1350— 2150 A) and U4 (1050-2150 A). We have published the observational results in the Celescope catalog of ultraviolet stellar observations (Davis, Deutschman & Haramundanis 1973). I have studied these results, together with relevant ground-based data, to determine the distribution of interstellar dust and variations of the interstellar extinction law with the position in the galaxy. Results from the data contained in the Celescope catalogue have been prepared for publication (Peytremann & Davis 1974)- These results have now been refined and expanded to include new ground-based U, B, V, and H(3 photometry acquired at Kitt Peak National Observatory, as well as new observations by W. A. Deutschman and R. Schild at Cerro Tololo Inter-American Observatory

Models for Interstellar Extinction in the Galaxy

2005 ◽  
Vol 130 (2) ◽  
pp. 659-673 ◽  
Author(s):  
E. B. Amôres ◽  
J. R. D. Lépine
Keyword(s):  
Interstellar Extinction ◽  
The Galaxy

scholarly journals Dust absorption and scattering in the silicon K-edge

2019 ◽  
Vol 627 ◽  
pp. A16 ◽  
Author(s):  
S. T. Zeegers ◽  
E. Costantini ◽  
D. Rogantini ◽  
C. P. de Vries ◽  
H. Mutschke ◽  
...  
Keyword(s):  
Interstellar Dust ◽  
Galactic Center ◽  
Interstellar Extinction ◽  
Line Of Sight ◽  
X Rays ◽  
Laboratory Measurements ◽  
Galactocentric Distance ◽  
Synchrotron Facility ◽  
The Galaxy ◽  
Low Mass

Context. The composition and properties of interstellar silicate dust are not well understood. In X-rays, interstellar dust can be studied in detail by making use of the fine structure features in the Si K-edge. The features in the Si K-edge offer a range of possibilities to study silicon-bearing dust, such as investigating the crystallinity, abundance, and the chemical composition along a given line of sight. Aims. We present newly acquired laboratory measurements of the silicon K-edge of several silicate-compounds that complement our measurements from our earlier pilot study. The resulting dust extinction profiles serve as templates for the interstellar extinction that we observe. The extinction profiles were used to model the interstellar dust in the dense environments of the Galaxy. Methods. The laboratory measurements, taken at the Soleil synchrotron facility in Paris, were adapted for astrophysical data analysis and implemented in the SPEX spectral fitting program. The models were used to fit the spectra of nine low-mass X-ray binaries located in the Galactic center neighborhood in order to determine the dust properties along those lines of sight. Results. Most lines of sight can be fit well by amorphous olivine. We also established upper limits on the amount of crystalline material that the modeling allows. We obtained values of the total silicon abundance, silicon dust abundance, and depletion along each of the sightlines. We find a possible gradient of 0.06 ± 0.02 dex/kpc for the total silicon abundance versus the Galactocentric distance. We do not find a relation between the depletion and the extinction along the line of sight.

scholarly journals Graphite Grains and Graphite-Core-Ice-Mantle Grains

1965 ◽  
Vol 7 ◽  
pp. 167-184
Author(s):  
N. C. Wickramasinghe
Keyword(s):  
Ad Hoc ◽  
Narrow Range ◽  
Interstellar Extinction ◽  
Characteristic Size ◽  
Size Parameter ◽  
Grain Sizes ◽  
Desirable Feature ◽  
The Galaxy ◽  
The Mean ◽  
Grain Model

Among the First Requirements for a Grain Model is that it should explain the observed interstellar extinction law or laws as they are now understood; a desirable feature of such a model is that as few ad hoc assumptions be made as possible.A criticism of the classical ice grain theory is that a very narrow range of grain sizes (or a size distribution with a size parameter specified to within a few percent) must be postulated in order to obtain a fit with the mean extinction law. (See refs. 1 and 2.) While it is true that regional variations in the extinction law have recently been detected (refs. 3 and 4), the best available evidence indicates that the extinction law is quite uniform when averaged over individual large regions which are widely distributed in the galaxy. (See ref. 5 and paper by Nandy in the present compilation.) The restriction of particle size to a radius within a few percent of an arbitrarily specified value (r ≈ 3 X 10-5 cm) demanded on the basis of pure ice absorption is therefore considered quite unsatis-factory, particularly in view of the fact that no characteristic size parameter emerges from the Oort-van de Hulst theory for the formation and destruction of grains. (See ref. 6.)

scholarly journals The Problem of the UV Interstellar Absorption Band at 2200A

1977 ◽  
Vol 43 ◽  
pp. 26-26
Author(s):  
D.J. Carnochan ◽  
K. Nandy ◽  
A.J. Willis ◽  
R. Wilson
Keyword(s):  
Galactic Plane ◽  
Interstellar Extinction ◽  
Extinction Curve ◽  
Absorption Feature ◽  
The Sun ◽  
The Galaxy ◽  
Satellite Experiment ◽  
Using Data ◽  
Broad Scale ◽  
Pronounced Peak

The ultraviolet interstellar extinction curve from 2740Å to 1350Å has been obtained using data from the S2/68 satellite experiment. The extinction increases into the ultraviolet and shows a pronounced peak at 2200Å. This is interpreted as a general scattering continuum with a strong absorption feature superposed on it at 2200Å. The profile of the feature appears to be symmetrical and has a half-width of 360Å. There is a strong correlation between the strength of the feature and the scattering part of the curve in both the ultraviolet and the visible. On a broad scale the shape of the extinction curve is constant showing no variation with distance from the sun, direction around the galaxy, and height above the galactic plane.

scholarly journals The study of unclassified B[e] stars and candidates in the Galaxy and Magellanic Clouds†

2019 ◽  
Vol 488 (1) ◽  
pp. 1090-1110 ◽  
Author(s):  
C A H Condori ◽  
M Borges Fernandes ◽  
M Kraus ◽  
D Panoglou ◽  
C A Guerrero
Keyword(s):  
Main Sequence ◽  
Interstellar Extinction ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
Light Curves ◽  
Evolutionary Stage ◽  
The Third ◽  
The Galaxy ◽  
Gaia Dr2

ABSTRACT We investigated 12 unclassified B[e] stars or candidates, 8 from the Galaxy, 2 from the Large Magellanic Cloud (LMC), and 2 from the Small Magellanic Cloud (SMC). Based on the analysis of high-resolution spectroscopic (FEROS) and photometric data, we confirmed the presence of the B[e] phenomenon for all objects of our sample, except for one (IRAS 07455-3143). We derived their effective temperature, spectral type, luminosity class, interstellar extinction and, using the distances from Gaia DR2, we obtained their bolometric magnitude, luminosity, and radius. Modelling of the forbidden lines present in the FEROS spectra revealed information about the kinematics and geometry of the circumstellar medium of these objects. In addition, we analysed the light curves of four stars, finding their most probable periods. The evolutionary stage of 11 stars of our sample is suggested from their position on the HR diagram, taking into account evolutionary tracks of stars with solar, LMC, and SMC metallicities. As results, we identified B and B[e] supergiants, B[e] stars probably at the main sequence or close to its end, post-AGB and HAeB[e] candidates, and A[e] stars in the main sequence or in the pre-main sequence. However, our most remarkable results are the identification of the third A[e] supergiant (ARDB 54, the first one in the LMC), and of an ‘LBV impostor’ in the SMC (LHA 115-N82).

scholarly journals GALACTICNUCLEUS: A high angular-resolution JHKs imaging survey of the Galactic centre

2020 ◽  
Vol 641 ◽  
pp. A141
Author(s):  
F. Nogueras-Lara ◽  
R. Schödel ◽  
N. Neumayer ◽  
E. Gallego-Cano ◽  
B. Shahzamanian ◽  
...  
Keyword(s):  
Stellar Population ◽  
Near Infrared ◽  
Angular Resolution ◽  
Interstellar Extinction ◽  
Extinction Curve ◽  
Line Of Sight ◽  
Galactic Centre ◽  
High Angular Resolution ◽  
The Galaxy ◽  
Red Clump

Context. The characterisation of the extinction curve in the near-infrared (NIR) is fundamental to analysing the structure and stellar population of the Galactic centre (GC), whose analysis is hampered by the extreme interstellar extinction (AV ~ 30 mag) that varies on arc-second scales. Recent studies indicate that the behaviour of the extinction curve might be more complex than previously assumed, pointing towards a variation of the extinction curve as a function of wavelength. Aims. We aim to analyse the variations of the extinction index, α, with wavelength, line-of-sight, and absolute extinction, extending previous analyses to a larger area of the innermost regions of the Galaxy. Methods. We analysed the whole GALACTICNUCLEUS survey, a high-angular resolution (~0.2″) JHKs NIR survey specially designed to observe the GC in unprecedented detail. It covers a region of ~6000 pc2, comprising fields in the nuclear stellar disc, the inner bulge, and the transition region between them. We applied two independent methods based on red clump (RC) stars to constrain the extinction curve and analysed its variation superseding previous studies. Results. We used more than 165 000 RC stars and increased the size of the regions analysed significantly to confirm that the extinction curve varies with the wavelength. We estimated a difference Δα = 0.21 ± 0.07 between the obtained extinction indices, αJH = 2.44 ± 0.05 and αHKs = 2.23 ± 0.05. We also concluded that there is no significant variation of the extinction curve with wavelength, with the line-of-sight or the absolute extinction. Finally, we computed the ratios between extinctions, AJ∕AH = 1.87 ± 0.03 and AH/AKs = 1.84 ± 0.03, consistent with all the regions of the GALACTICNUCLEUS catalogue.

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