Dust Extinction, Attenuation, and Emission

2021 ◽  
pp. 96-112
Author(s):  
Karl D. Gordon
Keyword(s):  
Dust Extinction

scholarly journals EARLINET dust observations vs. BSC-DREAM8b modeled profiles: 12-year-long systematic comparison at Potenza, Italy

2014 ◽  
Vol 14 (16) ◽  
pp. 8781-8793 ◽  
Author(s):  
L. Mona ◽  
N. Papagiannopoulos ◽  
S. Basart ◽  
J. Baldasano ◽  
I. Binietoglou ◽  
...  
Keyword(s):  
Center Of Mass ◽  
Saharan Dust ◽  
Raman Lidar ◽  
Dust Layer ◽  
Systematic Comparison ◽  
Dust Extinction ◽  
Lidar Measurements ◽  
Order Of Magnitude ◽  
Lidar Ratio ◽  
532 Nm

Abstract. In this paper, we report the first systematic comparison of 12-year modeled dust extinction profiles vs. Raman lidar measurements. We use the BSC-DREAM8b model, one of the most widely used dust regional models in the Mediterranean, and Potenza EARLINET lidar profiles for Saharan dust cases, the largest one-site database of dust extinction profiles. A total of 310 dust cases were compared for the May 2000–July 2012 period. The model reconstructs the measured layers well: profiles are correlated within 5% of significance for 60% of the cases and the dust layer center of mass as measured by lidar and modeled by BSC-DREAM8b differ on average 0.3 ± 1.0 km. Events with a dust optical depth lower than 0.1 account for 70% of uncorrelated profiles. Although there is good agreement in terms of profile shape and the order of magnitude of extinction values, the model overestimates the occurrence of dust layer top above 10 km. Comparison with extinction profiles measured by the Raman lidar shows that BSC-DREAM8b typically underestimates the dust extinction coefficient, in particular below 3 km. Lowest model–observation differences (below 17%) correspond to a lidar ratio at 532 nm and Ångström exponent at 355/532 nm of 60 ± 13 and 0.1 ± 0.6 sr, respectively. These are in agreement with values typically observed and modeled for pure desert dust. However, the highest differences (higher than 85%) are typically related to greater Ångström values (0.5 ± 0.6), denoting smaller particles. All these aspects indicate that the level of agreement decreases with an increase in mixing/modification processes.

scholarly journals Improvement of CALIOP Cloud Masking Algorithms for Better Estimation of Dust Extinction Profiles

2014 ◽  
Vol 92 (5) ◽  
pp. 433-455 ◽  
Author(s):  
Yoshitaka JIN ◽  
Kenji KAI ◽  
Hajime OKAMOTO ◽  
Yuichiro HAGIHARA
Keyword(s):  
Dust Extinction

scholarly journals 3D Galactic dust extinction mapping with multiband photometry

2014 ◽  
Vol 438 (4) ◽  
pp. 2938-2953 ◽  
Author(s):  
R. J. Hanson ◽  
C. A. L. Bailer-Jones
Keyword(s):  
Dust Extinction

scholarly journals Dark dust and single-cloud sightlines in the ISM

2020 ◽  
Vol 641 ◽  
pp. A35
Author(s):  
R. Siebenmorgen ◽  
J. Krełowski ◽  
J. Smoker ◽  
G. Galazutdinov ◽  
S. Bagnulo
Keyword(s):  
Interstellar Medium ◽  
Spectral Type ◽  
Column Density ◽  
Resolving Power ◽  
High Resolution Spectroscopy ◽  
Luminosity Distance ◽  
Ob Stars ◽  
Dust Extinction ◽  
Heating Source ◽  
Dust Component

The precise characteristics of clouds and the nature of dust in the diffuse interstellar medium can only be extracted by inspecting the rare cases of single-cloud sightlines. In our nomenclature such objects are identified by interstellar lines, such as K I, that show at a resolving power of λ∕Δλ ~ 75 000 one dominating Doppler component that accounts for more than half of the observed column density. We searched for such sightlines using high-resolution spectroscopy towards reddened OB stars for which far-UV extinction curves are known. We compiled a sample of 186 spectra, 100 of which were obtained specifically for this project with UVES. In our sample we identified 65 single-cloud sightlines, about half of which were previously unknown. We used the CH/CH+ line ratio of our targets to establish whether the sightlines are dominated by warm or cold clouds. We found that CN is detected in all cold (CH/CH+ > 1) clouds, but is frequently absent in warm clouds. We inspected the WISE (3−22 μm) observed emission morphology around our sightlines and excluded a circumstellar nature for the observed dust extinction. We found that most sightlines are dominated by cold clouds that are located far away from the heating source. For 132 stars, we derived the spectral type and the associated spectral type-luminosity distance. We also applied the interstellar Ca II distance scale, and compared these two distance estimates with Gaia parallaxes. These distance estimates scatter by ~40%. By comparing spectral type-luminosity distances with those of Gaia, we detected a hidden dust component that amounts to a few mag of extinction for eight sightlines. This dark dust is populated by ≳ 1 μm large grains and predominately appears in the field of the cold interstellar medium.

Dust extinction from Paschen-Balmer lines

1996 ◽  
pp. 285-286
Author(s):  
L. Petersen ◽  
T. Christensen ◽  
P. Gammelgaard
Keyword(s):  
Dust Extinction ◽  
Balmer Lines

scholarly journals The MAGNUM survey: different gas properties in the outflowing and disc components in nearby active galaxies with MUSE

2019 ◽  
Vol 622 ◽  
pp. A146 ◽  
Author(s):  
M. Mingozzi ◽  
G. Cresci ◽  
G. Venturi ◽  
A. Marconi ◽  
F. Mannucci ◽  
...  
Keyword(s):  
Radiation Field ◽  
Galactic Nuclei ◽  
Seyfert Galaxies ◽  
Dust Extinction ◽  
Physical Conditions ◽  
Spatially Resolved ◽  
Line Region ◽  
Central Regions ◽  
Stellar Velocity ◽  
Narrow Line Region

We investigated the interstellar medium (ISM) properties of the disc and outflowing gas in the central regions of nine nearby Seyfert galaxies, all characterised by prominent conical or biconical outflows. These objects are part of the Measuring Active Galactic Nuclei Under MUSE Microscope (MAGNUM) survey, which aims to probe their physical conditions and ionisation mechanism by exploiting the unprecedented sensitivity of the Multi Unit Spectroscopic Explorer (MUSE), combined with its spatial and spectral coverage. Specifically, we studied the different properties of the gas in the disc and in the outflow with spatially and kinematically resolved maps by dividing the strongest emission lines in velocity bins. We associated the core of the lines with the disc, consistent with the stellar velocity, and the redshifted and the blueshifted wings with the outflow. We measured the reddening, density, ionisation parameter, and dominant ionisation source of the emitting gas for both components in each galaxy. We find that the outflowing gas is characterised by higher values of density and ionisation parameter than the disc, which presents a higher dust extinction. Moreover, we distinguish high- and low-ionisation regions across the portion of spatially resolved narrow-line region (NLR) traced by the outflowing gas. The high-ionisation regions characterised by the lowest [N II]/Hα and [S II]/Hα line ratios generally trace the innermost parts along the axis of the emitting cones where the [S III]/[S II] line ratio is enhanced, while the low-ionisation regions follow the cone edges and/or the regions perpendicular to the axis of the outflows, also characterised by a higher [O III] velocity dispersion. A possible scenario to explain these features relies on the presence of two distinct populations of line emitting clouds: one is optically thin to the radiation and is characterised by the highest excitation, while the other is optically thick and is impinged by a filtered, and thus harder, radiation field which generates strong low-excitation lines. The highest values of [N II]/Hα and [S II]/Hα line ratios may be due to shocks and/or a hard filtered radiation field from the active galactic nucleus.

scholarly journals Results of the SiO Maser Survey of the Galactic Bulge IRAS Sources

1996 ◽  
Vol 169 ◽  
pp. 119-124
Author(s):  
S. Deguchi ◽  
N. Ukita ◽  
H. Izumiura ◽  
T. Ono ◽  
Y. Nakada ◽  
...  
Keyword(s):  
Point Source ◽  
Near Infrared ◽  
Radial Velocities ◽  
Galactic Bulge ◽  
Entire Region ◽  
Dust Extinction ◽  
Optical Wavelengths

Evidence for the bar structure in our Galaxy has been shown by Blitz and Spergel (1991b) based on the near-infrared maps of the bulge, by Nakada et al. (1991) based on IRAS point source catalogue, and more clearly by recent COBE maps. However, no clear “dynamical” signature of the bulge bar has been found yet. At optical wavelengths, stellar radial velocities of the bulge stars were observed only at the optical windows and were not observed for the entire region of the bulge because of the dust extinction in this direction.

Sign in / Sign up

Export Citation Format

Share Document