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 Intrinsic polarization of elongated porous dust grains

2019 ◽  
Vol 488 (1) ◽  
pp. 1211-1219 ◽  
Author(s):  
Florian Kirchschlager ◽  
Gesa H-M Bertrang ◽  
Mario Flock
Keyword(s):  
Grain Size ◽  
Thermal Emission ◽  
Far Infrared ◽  
Dipole Approximation ◽  
Dust Grains ◽  
Intrinsic Polarization ◽  
Axis Ratio ◽  
Dust Grain ◽  
The Impact ◽  
Protoplanetary Discs

ABSTRACT Observations of the Atacama Large Millimeter Array (ALMA) revealed recently polarized radiation of several protoplanetary discs in the (sub)millimetre wavelength range. Besides self-scattering of large particles, thermal emission by elongated grains is a potential source for the detected polarization signal. We calculate the wavelength dependent absorption and intrinsic polarization of spheroidally shaped, micrometre, and submillimetre sized dust grains using the discrete dipole approximation. In particular, we analyse the impact of dust grain porosity that appears to be present in discs when small grains coagulate to form larger aggregates. For the first time, our results show that (a) the intrinsic polarization decreases for increasing grain porosity and (b) the polarization orientation flips by 90 deg for certain ratios of wavelength to grain size. We present a new method to constrain grain porosity and the grain size in protoplanetary discs using multiwavelength polarization observations in the far-infrared to millimetre wavelengths. Finally, we find that moderate grain porosities ($\mathcal {P}\lesssim 0.7$) potentially explain the observed polarization fraction in the system HD 142527 while highly porous grains ($\mathcal {P}\gt 0.7$) fail unless the grain’s axis ratio is extraordinarily large.

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 Evolution of grain size distribution in galactic discs

2020 ◽  
Vol 636 ◽  
pp. A18 ◽  
Author(s):  
M. Relaño ◽  
U. Lisenfeld ◽  
K.-C. Hou ◽  
I. De Looze ◽  
J. M. Vílchez ◽  
...  
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Radial Distribution ◽  
Molecular Gas ◽  
Evolutionary Stage ◽  
Dust Grains ◽  
Cosmological Simulations ◽  
Dust Grain ◽  
Dust Evolution

Context. Dust is formed out of stellar material and it is constantly affected by different mechanisms occurring in the interstellar medium. Depending on their size, the behaviour of dust grains vary under these mechanisms and, therefore, the dust grain size distribution evolves as part of the dust evolution itself. Following how the grain size distribution evolves is a difficult computing task that has only recently become the subject of consideration. Smoothed particle hydrodynamic (SPH) simulations of a single galaxy, together with cosmological simulations, are producing the first predictions of the evolution of dust grain size distribution. Aims. We compare, for the first time, the evolution of the dust grain size distribution as predicted by SPH simulations and results from observations. We are able to validate not only the predictions of the evolution of the small-to-large grain mass ratio (DS/DL) within a galaxy, but we also provide observational constraints for recent cosmological simulations that include the grain size distribution in the dust evolution framework. Methods. We selected a sample of three spiral galaxies with different masses: M 101, NGC 628, and M 33. We fitted the dust spectral energy distribution across the disc of each object and derived the abundance of the different grain types included in the dust model. We analysed how the radial distribution of the relative abundance of the different grain size populations changes over the whole disc within each galaxy. The DS/DL ratio as a function of the galactocentric distance and metallicity is directly compared to what has been predicted by the SPH simulations. Results. We find a good agreement between the observed radial distribution of DS/DL and what was obtained from the SPH simulations of a single galaxy. The comparison agrees with the expected evolutionary stage of each galaxy. We show that the central parts of NGC 628 at a high metallicity and with a high molecular gas fraction are mainly affected not only by accretion, but also by the coagulation of dust grains. The centre of M 33, having a lower metallicity and lower molecular gas fraction, presents an increase in the DS/DL ratio, demonstrating that shattering is very effective for creating a large fraction of small grains. Finally, the observational results provided by our galaxies confirm the general relations predicted by the cosmological simulations based on the two-grain size approximation. However, we also present evidence that the simulations could be overestimating the amount of large grains in high massive galaxies.

scholarly journals Connecting the Interstellar Gas and Dust Properties in Distant Galaxies Using Quasar Absorption Systems

2015 ◽  
Vol 11 (S315) ◽  
Author(s):  
Monique C. Aller ◽  
Varsha P. Kulkarni ◽  
Donald G. York ◽  
Daniel E. Welty ◽  
Giovanni Vladilo ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Absorption Feature ◽  
Dust Grains ◽  
Interstellar Gas ◽  
Chemical Enrichment ◽  
Normal Galaxies ◽  
History Of ◽  
Dust Grain ◽  
Grain Properties

AbstractGas and dust grains are fundamental components of the interstellar medium and significantly impact many of the physical processes driving galaxy evolution, such as star-formation, and the heating, cooling, and ionization of the interstellar material. Quasar absorption systems (QASs), which trace intervening galaxies along the sightlines to luminous quasars, provide a valuable tool to directly study the properties of the interstellar gas and dust in distant, normal galaxies. We have established the presence of silicate dust grains in at least some gas-rich QASs, and find that they exist at higher optical depths than expected for diffuse gas in the Milky Way. Differences in the absorption feature shapes additionally suggest variations in the silicate dust grain properties, such as in the level of grain crystallinity, from system-to-system. We present results from a study of the gas and dust properties of QASs with adequate archival IR data to probe the silicate dust grain properties. We discuss our measurements of the strengths of the 10 and 18 μm silicate dust absorption features in the QASs, and constraints on the grain properties (e.g., composition, shape, crystallinity) based on fitted silicate profile templates. We investigate correlations between silicate dust abundance, reddening, and gas metallicity, which will yield valuable insights into the history of star formation and chemical enrichment in galaxies.

scholarly journals Detecting shocked intergalactic gas with X-ray and radio observations

2019 ◽  
Vol 627 ◽  
pp. A5 ◽  
Author(s):  
F. Vazza ◽  
S. Ettori ◽  
M. Roncarelli ◽  
M. Angelinelli ◽  
M. Brüggen ◽  
...  
Keyword(s):  
Large Scale ◽  
Intergalactic Medium ◽  
Thermal Emission ◽  
Intergalactic Gas ◽  
Radio Observations ◽  
X Ray ◽  
Large Scale Structures ◽  
Hot Gas ◽  
Scale Structures ◽  
Radio Band

Detecting the thermal and non-thermal emission from the shocked cosmic gas surrounding large-scale structures represents a challenge for observations, as well as a unique window into the physics of the warm-hot intergalactic medium. In this work, we present synthetic radio and X-ray surveys of large cosmological simulations in order to assess the chances of jointly detecting the cosmic web in both frequency ranges. We then propose best observing strategies tailored for existing (LOFAR, MWA, and XMM) or future instruments (SKA-LOW and SKA-MID, Athena, and eROSITA). We find that the most promising targets are the extreme peripheries of galaxy clusters in an early merging stage, where the merger causes the fast compression of warm-hot gas onto the virial region. By taking advantage of a detection in the radio band, future deep X-ray observations will probe this gas in emission, and help us to study plasma conditions in the dynamic warm-hot intergalactic medium with unprecedented detail.

scholarly journals Catalytic Role of Refractory Interstellar Grain Analogs on H2 Formation

2021 ◽  
Vol 8 ◽  
Author(s):  
Tushar Suhasaria ◽  
Vito Mennella
Keyword(s):  
Molecular Hydrogen ◽  
Laboratory Experiments ◽  
Dust Grains ◽  
Interstellar Gas ◽  
Complex Molecules ◽  
Catalytic Role ◽  
H2 Formation ◽  
Dust Grain

Refractory dust grains have an important role to play in the chemistry of star and planet-forming regions. Their surfaces interact with interstellar gas and act as a catalyst for the formation of simple and complex molecules in space. Several mechanisms have been invoked to explain how molecular hydrogen is formed in reactions on dust grain surfaces in different regions of space. In this article, we give an overview of our understanding of the laboratory experiments, conducted over the last 20 years, that deal with H2 formation on interstellar grain analogs in space simulated conditions.

Seasonal Change in the Deep Atmosphere of Uranus, 1981 to 2012

2021 ◽  
Author(s):  
Mark Hofstadter ◽  
Alexander Akins ◽  
Byran Butler
Keyword(s):  
Southern Hemisphere ◽  
Late Summer ◽  
Circulation Pattern ◽  
Giant Planets ◽  
Radio Observations ◽  
Data Set ◽  
Time Line ◽  
Very Large Array ◽  
Planetary Scale ◽  
Water Cloud

<p>Our team is using radio observations of Uranus, collected with the Very Large Array (VLA) telescope, to track seasonal changes in the deep troposphere of Uranus between 1981 and the present.  We previously reported on changes between 1981 and 1994, as the Southern Hemisphere moved from mid- to late-summer (Hofstadter and Butler 2003, Icarus 165, https://doi.org/10.1016/S0019-1035(03)00174-X).  During that time, the distribution of opacity sources in the atmosphere (now thought primarily to be H<sub>2</sub>S) changed in such a way as to suggest an increase in the strength of the planetary-scale circulation pattern in the 5 to 50 bar region of the atmosphere.  More specifically, using wavelengths from 1 to 20 cm, we found that regions poleward of 45 degrees latitude in the Southern Hemisphere are significantly depleted in absorbers compared to more equatorial latitudes, down to a pressure of about 50 bars (which is near the top of where a liquid water cloud is expected to form).  This opacity distribution could be explained by a planetary-scale circulation pattern, with absorber rich air parcels moving upward in equatorial regions, being depleted in absorbers by condensation at higher altitudes, and then moving poleward and descending, keeping the pole depleted in absorbers.  We found that the opacity difference between the pole and equator increased between the 1980's and the 1990's, suggesting a strengthening of the assumed circulation pattern.  Radio observations by our group and others since 1994 have shown that the Northern Hemisphere is roughly symmetric with the Southern, and that smaller-scale latitudinal banding exists (e.g., Molter et al. 2020 https://arxiv.org/abs/2010.11154).  </p><p>We are currently analyzing additional Uranus data collected at the VLA, and will present results from a subset of those observations taken in 2012 (during Southern Fall).  We will also discuss plans for extending the time line to the present.  The complete data set will span half a uranian year, allowing all seasons to be observed.  We will also discuss how the composition and chemistry of the ice giant planets (Uranus and Neptune) differ from those of the gas giants (Jupiter and Saturn).</p>

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