scholarly journals Polarization of Thermal Emission from Aligned Dust Grains under an Anisotropic Radiation Field

2000 ◽  
Vol 533 (1) ◽  
pp. 298-303 ◽  
Author(s):  
Takashi Onaka
Keyword(s):  
Radiation Field ◽  
Thermal Emission ◽  
Dust Grains

scholarly journals From grains to pebbles: the influence of size distribution and chemical composition on dust emission properties

2019 ◽  
Vol 631 ◽  
pp. A88 ◽  
Author(s):  
N. Ysard ◽  
M. Koehler ◽  
I. Jimenez-Serra ◽  
A. P. Jones ◽  
L. Verstraete
Keyword(s):  
Chemical Composition ◽  
Size Distribution ◽  
Spectral Index ◽  
Thermal Emission ◽  
Spectral Energy ◽  
Internal Source ◽  
Dust Grains ◽  
Grain Composition ◽  
Dust Mass ◽  
Dust Composition

Context. The size and chemical composition of interstellar dust grains are critical in setting the dynamical, physical, and chemical evolution of all the media in which they are present. Thanks to facilities such as the Atacama Large Millimeter/submillimeter Array (ALMA) and, in the future, the Square Kilometer Array (SKA), thermal emission in the (sub)millimetre to centimetre domain has become a very convenient way to trace grain properties. Aims. Our aim is to understand the influence of the composition and size distribution of dust grains on the shape of their spectral energy distribution (peak position, spectral index) in dense interstellar regions such as molecular clouds, prestellar cores, young stellar objects, and protoplanetary discs. Methods. Starting from the optical constants defined in The Heterogeneous dust Evolution Model for Interstellar Solids (THEMIS) for amorphous hydrogenated carbon grains and amorphous silicates in addition to water ice, we defined six material mixtures that we believe are representative of the expected dust composition in dense interstellar regions. The optical properties of 0.01 μm to 10 cm grains were then calculated with effective medium and Mie theories. The corresponding spectral energy distributions were subsequently calculated for isolated clouds either externally heated by the standard interstellar radiation field alone or in addition to an internal source. Results. The three main outcomes of this study are as follows. Firstly, the dust mass absorption coefficient strongly depends on both grain composition and size distribution potentially leading to errors in dust mass estimates by factors up to ~3 and 20, respectively. Secondly, it appears almost impossible to retrieve the grain composition from the (sub)millimetre to centimetre thermal emission shape alone as its spectral index for λ ≳ 3 mm does not depend on dust composition. Thirdly, using the “true” dust opacity spectral index to estimate grain sizes may lead to erroneous findings as the observed spectral index can be highly modified by the dust temperature distribution along the line of sight, which depends on the specific heating source and on the geometry of the studied interstellar region. Conclusions. Based on the interpretation of only the spectral shape of (sub)millimetre to centimetre observational data, the determination of the dust masses, compositions, and sizes are highly uncertain.

scholarly journals Millimeter-sized Dust Grains Surviving the Water-sublimating Temperature in the Inner 10 au of the FU Ori Disk

2021 ◽  
Vol 923 (2) ◽  
pp. 270
Author(s):  
Hauyu Baobab Liu ◽  
An-Li Tsai ◽  
Wen Ping Chen ◽  
Jin Zhong Liu ◽  
Xuan Zhang ◽  
...  
Keyword(s):  
Grain Size ◽  
Binary Stars ◽  
Thermal Emission ◽  
Dust Grains ◽  
Radio Observations ◽  
Very Large Array ◽  
Water Ice ◽  
Fu Ori ◽  
June July ◽  
Dust Grain

Abstract Previous observations have shown that the ≲10 au, ≳400 K hot inner disk of the archetypal accretion outburst young stellar object, FU Ori, is dominated by viscous heating. To constrain dust properties in this region, we have performed radio observations toward this disk using the Karl G. Jansky Very Large Array in 2020 June–July, September, and November. We also performed complementary optical photometric monitoring observations. We found that the dust thermal emission from the hot inner disk mid-plane of FU Ori has been approximately stationary and the maximum dust grain size is ≳1.6 mm in this region. If the hot inner disk of FU Ori, which is inward of the 150–170 K water snowline, is turbulent (e.g., corresponding to a Sunyaev & Shakura viscous α t ≳ 0.1), or if the actual maximum grain size is still larger than the lower limit we presently constrain, then as suggested by the recent analytical calculations and the laboratory measurements, water-ice-free dust grains may be stickier than water-ice-coated dust grains in protoplanetary disks. Additionally, we find that the free–free emission and the Johnson B- and V-band magnitudes of these binary stars were brightening in 2016–2020. The optical and radio variability might be related to the dynamically evolving protostellar- or disk-accretion activities. Our results highlight that the hot inner disks of outbursting objects are important laboratories for testing models of dust grain growth. Given the active nature of such systems, to robustly diagnose the maximum dust grain sizes, it is important to carry out coordinated multiwavelength radio observations.

scholarly journals Absorption and Emission of EUV Radiation by the Local ISM

1984 ◽  
Vol 81 ◽  
pp. 169-184 ◽  
Author(s):  
Francesco Paresce
Keyword(s):  
Radiation Field ◽  
Thermal Emission ◽  
Cataclysmic Variables ◽  
Physical Structure ◽  
Similar Data ◽  
Interstellar Gas ◽  
B Stars ◽  
Available Information ◽  
Near Future ◽  
Compact Sources

AbstractThe Berkeley EUV telescope flown on the Apollo Soyuz mission in July, 1975 established the existence of a measurable flux of EUV radiation (100 ≤ λ ≤ 1000 Å) originating from sources outside the solar system. White dwarfs, flare stars and cataclysmic variables were discovered to be relatively intense compact sources of EUV photons. Moreover, this and other subsequent experiments have strongly suggested the presence of a truly diffuse component of the EUV radiation field possibly due to thermal emission from hot (T > 105 K) interstellar gas located in the general vicinity of the sun (r ≃ 100 parsecs.) Closer to the HI, 912 Å edge, the effect of a few hot O and B stars has been shown to be very important in establishing the interstellar flux density. All these results imply that the local ISM is immersed in a non-negligible EUV radiation field which, because of the strong coupling between EUV photons and matter, will play a crucial role in determining its physical structure. Conversely, of course, the local ISM is expected to leave a strong imprint on the EUV field reaching the terrestrial observer.The objective of this review will be to assemble and critically analyze the available information on the local ISM derived from the limited EUV observations carried out so far. These include measurements of the spectra of bright EUV sources that reveal clear evidence of H photo absorption at λ > 400 Å and of the He ionization edge at 228 Å. The EUV diffuse background is found to convey interesting information on the density, temperature and possible location of the hot ISM component that can be profitably compared with similar data on far uv absorption lines, principally OVI. The results discussed in this context will be shown to be quite useful in illuminating the path that future EUV sensitive observatories such as EUVE and Columbus might profitably follow in the near future.

scholarly journals Dipolar radiation from spinning dust grains coupled to an electromagnetic wave

2007 ◽  
Vol 73 (4) ◽  
pp. 555-563
Author(s):  
A. GUERREIRO ◽  
M. ELOY ◽  
J. T. MENDONÇA ◽  
R. BINGHAM
Keyword(s):  
Interstellar Dust ◽  
Thermal Emission ◽  
Microwave Emission ◽  
Dust Grains ◽  
Field Frequency ◽  
Background Magnetic Field ◽  
Spectral Components ◽  
Em Field ◽  
Dust Grain ◽  
Independent Parameters

AbstractIn this paper we investigate how the complex rotation and quivering motion of an elongated polarized dust grain in the presence of a monochromatic electromagnetic (EM) wave can produce dipolar emission with two distinct spectral components. We present a model for the emission of radiation by elongated polarized dust grains under the influence of both an external EM wave and a constant background magnetic field. The dust, exhibiting rotational motion at the external EM field frequency ω 0 as well as quivering motion at a frequency Ω0, proportional to the EM field amplitude, will radiate with frequencies that will depend on the external field wavelength and amplitude. The radiated spectra exhibits a frequency around ω0, and sidebands at ω0 ± ω0 and ω0± 2Ω0. Since the amplitude and the frequency of the background EM field are independent parameters, this model establishes a correlation between different spectral components of galactic dipolar emission, which may help to explain the correlation between a component of the Galactic microwave emission and the 100 μ m thermal emission from interstellar dust that has been recently measured.

scholarly journals Trajectories of Sublimating Interplanetary Dust Grains

1980 ◽  
Vol 90 ◽  
pp. 319-320
Author(s):  
G. H. Schwehm
Keyword(s):  
Grain Size ◽  
Temperature Distribution ◽  
Radiation Field ◽  
Heliocentric Distance ◽  
Equation Of Motion ◽  
Interplanetary Dust ◽  
Dust Particles ◽  
The Sun ◽  
Dust Grains ◽  
Interplanetary Dust Particles

The equation of motion for interplanetary dust particles close to the Sun has been solved numerically taking into consideration the interaction with the radiation field of the Sun and the temperature distribution as a function of grain size and heliocentric distance for different materials.

scholarly journals Dust in Planetary Nebulae

1989 ◽  
Vol 131 ◽  
pp. 117-128 ◽  
Author(s):  
Patrick F. Roche
Keyword(s):  
Thermal Emission ◽  
Planetary Nebulae ◽  
Central Star ◽  
Infrared Emission ◽  
Significant Fraction ◽  
Dust Grains ◽  
Ionized Gas ◽  
Total Luminosity

The presence of dust in planetary nebulae can be deduced in several ways - from the observed depletions of condensable elements, internal extinction and, most directly, through the detection of infrared emission from the dust grains. We know that there is a substantial amount of dust in planetary nebulae, and that a significant fraction of the total luminosity emerges in the infrared through thermal emission in most objects. However, a number of questions still largely remain unsolved, and perhaps the most pressing of these are that we do not yet have a satisfactory understanding of the ultraviolet, optical or infrared properties of the dust grains and we also do not yet know exactly where the emitting grains are located within the nebulae; for example, are they mixed with the ionized gas, or in neutral inclusions or perhaps in a disk around the central star?

scholarly journals Dust modeling of the combined ALMA and SPHERE datasets of HD 163296

2018 ◽  
Vol 614 ◽  
pp. A24 ◽  
Author(s):  
G. A. Muro-Arena ◽  
C. Dominik ◽  
L. B. F. M. Waters ◽  
M. Min ◽  
L. Klarmann ◽  
...  
Keyword(s):  
Near Infrared ◽  
Thermal Emission ◽  
Scattered Light ◽  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
Dust Grains ◽  
Outer Disk ◽  
Group I ◽  
Dust Evolution ◽  
Small Dust

Context. Multiwavelength observations are indispensable in studying disk geometry and dust evolution processes in protoplanetary disks. Aims. We aim to construct a three-dimensional model of HD 163296 that is capable of reproducing simultaneously new observations of the disk surface in scattered light with the SPHERE instrument and thermal emission continuum observations of the disk midplane with ALMA. We want to determine why the spectral energy distribution of HD 163296 is intermediary between the otherwise well-separated group I and group II Herbig stars. Methods. The disk was modeled using the Monte Carlo radiative transfer code MCMax3D. The radial dust surface density profile was modeled after the ALMA observations, while the polarized scattered light observations were used to constrain the inclination of the inner disk component and turbulence and grain growth in the outer disk. Results. While three rings are observed in the disk midplane in millimeter thermal emission at ~80, 124, and 200 AU, only the innermost of these is observed in polarized scattered light, indicating a lack of small dust grains on the surface of the outer disk. We provide two models that are capable of explaining this difference. The first model uses increased settling in the outer disk as a mechanism to bring the small dust grains on the surface of the disk closer to the midplane and into the shadow cast by the first ring. The second model uses depletion of the smallest dust grains in the outer disk as a mechanism for decreasing the optical depth at optical and near-infrared wavelengths. In the region outside the fragmentation-dominated regime, such depletion is expected from state-of-the-art dust evolution models. We studied the effect of creating an artificial inner cavity in our models, and conclude that HD 163296 might be a precursor to typical group I sources.

Dust in debris disk: Observations and laboratory experiments

2019 ◽  
Vol 15 (S350) ◽  
pp. 169-175
Author(s):  
Johan Olofsson
Keyword(s):  
Laboratory Experiments ◽  
Near Infrared ◽  
Thermal Emission ◽  
Radial Distance ◽  
Central Star ◽  
High Angular Resolution ◽  
Debris Disks ◽  
Dust Grains ◽  
Infrared Wavelengths ◽  
Small Dust

AbstractDebris disks are the natural by-products of the star and planet formation processes. Since the 1980’s several thousands of debris disks have been detected, and the presence of a disk is inferred by the detection of excess emission over the photospheric emission. This thermal emission arises from (micron-sized or slightly bigger) dust grains heated by the central star. However, in the vast majority of cases, these observations are not spatially resolving the radial distribution of the dust, resulting in strong degeneracies in the modeling approach (radial distance vs minimum grain size mostly). Therefore the properties of the small dust grains remained largely unconstrained until the arrival of high angular resolution instruments, especially at optical and near-infrared wavelengths. In these proceeding some of the main results are presented that have been obtained over the past few years on the properties of small dust grains in debris disks, and it is discussed how laboratory experiments contributed to put those results in context.

Interaction of relativistic dust grains with the solar radiation field

1993 ◽  
Vol 205 (2) ◽  
pp. 355-358 ◽  
Author(s):  
B. McBreen ◽  
S. Plunkett ◽  
C. J. Lambert
Keyword(s):  
Solar Radiation ◽  
Radiation Field ◽  
Dust Grains
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