scholarly journals Dust traps and the formation of cavities in transition discs: a millimetre to sub-millimetre comparison survey

2021 ◽  
Vol 502 (4) ◽  
pp. 5779-5796
Author(s):  
Brodie J Norfolk ◽  
Sarah T Maddison ◽  
Christophe Pinte ◽  
Nienke van der Marel ◽  
Richard A Booth ◽  
...  
Keyword(s):  
Dust Emission ◽  
Dust Grains ◽  
Cavity Size ◽  
Dust Trap ◽  
Compact Array ◽  
Clearing Mechanism

ABSTRACT The origin of the inner dust cavities observed in transition discs remains unknown. The segregation of dust and size of the cavity is expected to vary depending on which clearing mechanism dominates grain evolution. We present the results from the Discs Down Under program, an 8.8-mm continuum Australia Telescope Compact Array (ATCA) survey targeting 15 transition discs with large (≳20 au) cavities and compare the resulting dust emission to Atacama Large millimetre/sub-millimetre Array (ALMA) observations. Our ATCA observations resolve the inner cavity for 8 of the 14 detected discs. We fit the visibilities and reconstruct 1D radial brightness models for 10 sources with a S/N > 5σ. We find that, for sources with a resolved cavity in both wavebands, the 8.8 mm and sub-mm brightness distributions peak at the same radius from the star. We suggest that a similar cavity size for 8.8 mm and sub-mm dust grains is due to a dust trap induced by the presence of a companion.

scholarly journals Expelled grains from an unseen parent body around AU Microscopii

2017 ◽  
Vol 607 ◽  
pp. A65 ◽  
Author(s):  
É. Sezestre ◽  
J.-C. Augereau ◽  
A. Boccaletti ◽  
P. Thébault
Keyword(s):  
Point Source ◽  
Stellar Wind ◽  
Local Density ◽  
Dust Emission ◽  
Parent Body ◽  
Static Case ◽  
Dust Grains ◽  
Periodic Process ◽  
The Common ◽  
Debris Disk

Context. Recent observations of the edge-on debris disk of AU Mic have revealed asymmetric, fast outward-moving arch-like structures above the disk midplane. Although asymmetries are frequent in debris disks, no model can readily explain the characteristics of these features. Aims. We present a model aiming to reproduce the dynamics of these structures, more specifically their high projected speeds and their apparent position. We test the hypothesis of dust emitted by a point source and then expelled from the system by the strong stellar wind of this young M-type star. In this model we make the assumption that the dust grains follow the same dynamics as the structures, i.e., they are not local density enhancements. Methods. We perform numerical simulations of test particle trajectories to explore the available parameter space, in particular the radial location R0 of the dust producing parent body and the size of the dust grains as parameterized by the value of β (ratio of stellar wind and radiation pressure forces over gravitation). We consider the cases of a static and of an orbiting parent body. Results. We find that for all considered scenarios (static or moving parent body), there is always a set of (R0,β) parameters able to fit the observed features. The common characteristics of these solutions is that they all require a high value of β, of around 6. This means that the star is probably very active, and the grains composing the structures are submicronic in order for observable grains to reach such high β values. We find that the location of the hypothetical parent body is closer in than the planetesimal belt, around 8 ± 2 au (orbiting case) or 28 ± 7 au (static case). A nearly periodic process of dust emission appears, of 2 yr in the orbiting scenarios and 7 yr in the static case. Conclusions. We show that the scenario of sequential dust releases by an unseen point-source parent body is able to explain the radial behavior of the observed structures. We predict the evolution of the structures to help future observations discriminate between the different parent body configurations that have been considered. In the orbiting parent body scenario, we expect new structures to appear on the northwest side of the disk in the coming years.

scholarly journals Possible depletion of metals into dust grains in the core of the Centaurus cluster of galaxies

2019 ◽  
Vol 623 ◽  
pp. A17 ◽  
Author(s):  
K. Lakhchaura ◽  
F. Mernier ◽  
N. Werner
Keyword(s):  
Dust Emission ◽  
Temperature Structure ◽  
Central Metal ◽  
Dust Grains ◽  
Cluster Of Galaxies ◽  
Systematic Uncertainties ◽  
Central Regions ◽  
Metal Abundance ◽  
Reactive Metals ◽  
The Continuum

We present azimuthally averaged metal abundance profiles from a full, comprehensive, and conservative re-analysis of the deep (∼800 ks total net exposure) Chandra/ACIS-S observation of the Centaurus cluster core (NGC 4696). After carefully checking various sources of systematic uncertainties, including the choice of the spectral deprojection method, assumptions about the temperature structure of the gas, and uncertainties in the continuum modeling, we confirm the existence of a central drop in the abundances of the “reactive” elements Fe, Si, S, Mg, and Ca, within r≲10 kpc. The same drops are also found when analyzing the XMM-Newton/EPIC data (∼150 ks). Adopting our most conservative approach, we find that, unlike the central drops seen for Fe, Si, S, Mg and Ca, the abundance of the “nonreactive” element Ar is fully consistent with showing no central drop. This is further confirmed by the significant (> 3σ) central radial increase of the Ar/Fe ratio. Our results corroborate the previously proposed “dust depletion scenario”, in which central metal abundance drops are explained by the deposition of a significant fraction of centrally cooled reactive metals into dust grains present in the central regions of the Centaurus cluster. This is also supported by the previous findings that the extent of the metal abundance drops in NGC 4696 broadly coincides with the infrared dust emission.

Statistical analysis of dust grain tracks in Rosetta/OSIRIS images

2020 ◽  
Author(s):  
Pablo Lemos
Keyword(s):  
Radiation Pressure ◽  
Gas Flow ◽  
Dust Emission ◽  
Three Dimensional ◽  
Large Set ◽  
Dust Grains ◽  
Transform Method ◽  
Nucleus Surface ◽  
Dust Grain ◽  
Grain Properties

<p>In some of the images taken by OSIRIS, pieces of debris can be seen as bright tracks instead of points sources as result of the combination of movements of both particles and spacecraft. The properties of those tracks, such as orientation, length and total brightness, depend on various comets parameters, including the activity on the nucleus surface, capable of lifting and accelerating the particles, and the characteristics of dust grains, as grain sizes, spatial distribution, velocity, density and sensitivity to radiation pressure. Previous works have focused on retrieving some of these grain properties from the mentioned images, but since the images show the 2D projection of the 3D dust motion, they rely on different methods to obtain the distance between the camera and the debris.</p> <p>In this work, a new method to bypass this distance determination requirement is proposed. The main steps involved are <em>(i)</em> analyze a large set of images containing tracks generated by moving dust grains, and obtain distribution for selected track parameters (orientation, length, total brightness, etc.) using an algorithm based on the Hough transform method; <em>(ii)</em> compare these results with the ones obtained from artificial images, generated by modeling the three dimensional motion of the debris in the gas flow field of the comet, under the influence of gravity, radiation pressure and gaseous drag; <em>(iii)</em> iterate this process in order to refine the parameters characterizing the physical properties of the dust emission used by the model.</p>

Two Different Grain Distributions within the Protoplanetary Disk around HD 142527

2018 ◽  
Vol 14 (A30) ◽  
pp. 136-136
Author(s):  
Satoshi Ohashi ◽  
Akimasa Kataoka ◽  
Hiroshi Nagai
Keyword(s):  
Grain Size ◽  
Magnetic Fields ◽  
Dust Emission ◽  
Northern Region ◽  
Southern Region ◽  
Continuum Emission ◽  
Dust Grains ◽  
Size Segregation ◽  
Grain Alignment ◽  
Polarized Emission

AbstractThe origin of polarized emission from protoplanetary disks is uncertain. Three mechanisms have been proposed for such polarized emission so far, (1) grain alignment with magnetic fields, (2) grain alignment with radiation gradients, and (3) self-scattering of thermal dust emission. Aiming to observationally identify the polarization mechanisms, we present ALMA polarization observations of the 0.87 mm dust continuum emission toward the circumstellar disk around HD 142527 with a spatial resolution of ∼0.2 arcsec as shown in Ohashi et al. (2018). We confirm that the polarization vectors in the northern region are consistent with self-scattering because of a flip of the polarization vectors. Furthermore, we show that the polarization vectors in the southern region are consistent with grain alignment by magnetic fields, although self-scattering cannot be ruled out. To understand these differences between the polarization mechanisms, we propose a simple grain size segregation model: small dust grains ( $\mathbin{\lower.3ex\hbox{$\buildrel<\over {\smash{\scriptstyle\sim}\vphantom{_x}}$}} $ 100 microns) are dominant and aligned with magnetic fields in the southern region, and middle-sized (∼100 microns) grains in the upper layer emit self-scattered polarized emission in the northern region. The grain size near the middle plane in the northern region cannot be measured because the emission at 0.87 mm is optically thick. However, it can be speculated that larger dust grains ( $\mathbin{\lower.3ex\hbox{$\buildrel>\over {\smash{\scriptstyle\sim}\vphantom{_x}}$}} $ cm) may accumulate near this plane. These results are consistent with those of a previous analysis of the disk, in which large grain accumulation and optically thick emission from the northern region were found. This model is also consistent with theories where smaller dust grains are aligned with magnetic fields. We find that the magnetic fields are toroidal, at least in the southern region.

scholarly journals Probing the Cold Dust Emission in the AB Aur Disk: A Dust Trap in a Decaying Vortex?

2017 ◽  
Vol 846 (1) ◽  
pp. L3 ◽  
Author(s):  
Asunción Fuente ◽  
Clément Baruteau ◽  
Roberto Neri ◽  
Andrés Carmona ◽  
Marcelino Agúndez ◽  
...  
Keyword(s):  
Dust Emission ◽  
Dust Trap ◽  
Cold Dust

scholarly journals ALMA Band 3 polarimetric follow-up of a complete sample of faint PACO sources

2019 ◽  
Vol 489 (1) ◽  
pp. 470-486 ◽  
Author(s):  
V Galluzzi ◽  
G Puglisi ◽  
S Burkutean ◽  
E Liuzzo ◽  
M Bonato ◽  
...  
Keyword(s):  
Dust Emission ◽  
High Sensitivity ◽  
Band 3 ◽  
Host Galaxy ◽  
Complete Sample ◽  
Murchison Widefield Array ◽  
Compact Sources ◽  
Polarization Fraction ◽  
Compact Array

Abstract We present Atacama Large Millimetre/submillimiter Array (ALMA) high sensitivity ($\sigma _\mathrm{ P} \simeq 0.4\,$ mJy) polarimetric observations at $97.5\,$ GHz (Band 3) of a complete sample of 32 extragalactic radio sources drawn from the faint Planck–ATCA Co-eval Observations (PACO) sample (b &lt; −75°, compact sources brighter than $200\,$ mJy at $20\,$ GHz). We achieved a detection rate of $~97\, {\rm per\, cent}$ at $3\, \sigma$ (only 1 non-detection). We complement these observations with new Australia Telescope Compact Array (ATCA) data between 2.1 and $35\,$GHz obtained within a few months and with data published in earlier papers from our collaboration. Adding the co-eval GaLactic and Extragalactic All-sky Murchison widefield array (GLEAM) survey detections between $70\,$ and $230\,$ MHz for our sources, we present spectra over more than 3 decades in frequency in total intensity and over about 1.7 decades in polarization. The spectra of our sources are smooth over the whole frequency range, with no sign of dust emission from the host galaxy at mm wavelengths or of a sharp high frequency decline due, for example, to electron ageing. We do however find indications of multiple emitting components and present a classification based on the number of detected components. We analyse the polarization fraction behaviour and distributions up to $97\,$ GHz for different source classes. Source counts in polarization are presented at $95\,$ GHz.

scholarly journals Observing protoplanetary discs with the Square Kilometre Array – I. Characterizing pebble substructure caused by forming planets

2020 ◽  
Vol 498 (4) ◽  
pp. 5116-5127
Author(s):  
John D Ilee ◽  
Cassandra Hall ◽  
Catherine Walsh ◽  
Izaskun Jiménez-Serra ◽  
Christophe Pinte ◽  
...  
Keyword(s):  
Angular Resolution ◽  
Dust Emission ◽  
Image Plane ◽  
Raw Material ◽  
High Angular Resolution ◽  
High Fidelity ◽  
Dust Grains ◽  
Square Kilometre Array ◽  
A Current ◽  
Protoplanetary Discs

ABSTRACT High-angular-resolution observations of discs at mm wavelengths (on scales of a few au) are now commonplace, but there is a current lack of a comparable angular resolution for observations at cm wavelengths. This presents a significant barrier to improving our understanding of planet formation, in particular how dust grains grow from mm to cm sizes. In this paper, we examine the ability of the Square Kilometre Array (SKA) to observe dust substructure in a young, planet-forming disc at cm wavelengths. We use dusty hydrodynamics and continuum radiative transfer to predict the distribution and emission of 1-cm dust grains (or pebbles) within the disc, and simulate continuum observations with the current SKA1-MID design baseline at frequencies of 12.5 GHz (Band 5b, ∼2.4 cm) on 5–10 au scales. The SKA will provide high-fidelity observations of the cm dust emission substructure in discs for integration times totalling hundreds of hours. Radial structure can be obtained at a sufficient resolution and S/N from shorter (tens of hours) integration times by azimuthal averaging in the image plane. By modelling the intensity distribution directly in the visibility plane, it is possible to recover a similar level of (axisymmetric) structural detail from observations with integration times one to two orders of magnitude lower than required for high-fidelity imaging. Our results demonstrate that SKA1-MID will provide crucial constraints on the distribution and morphology of the raw material for building planets, the pebbles in protoplanetary discs.

scholarly journals Observational and theoretical constraints on the formation and early evolution of the first dust grains in galaxies at 5 < z < 10

2020 ◽  
Vol 637 ◽  
pp. A32 ◽  
Author(s):  
D. Burgarella ◽  
A. Nanni ◽  
H. Hirashita ◽  
P. Theulé ◽  
A. K. Inoue ◽  
...  
Keyword(s):  
First Generation ◽  
Dust Emission ◽  
Big Bang ◽  
Spectral Energy ◽  
Physical Parameters ◽  
Dust Grains ◽  
Star Forming ◽  
Low Metallicity ◽  
Early Galaxies ◽  
The Big Bang

Context. The first generation of stars were born a few hundred million years after the big bang. These stars synthesise elements heavier than H and He, which are later expelled into the interstellar medium, initiating the rise of metals. Within this enriched medium, the first dust grains were formed. This event is cosmologically crucial for molecule formation, as dust plays a major role by cooling low-metallicity star-forming clouds, which can fragment to create lower mass stars. Collecting information on these first dust grains is difficult because of the negative alliance of large distances and low dust masses. Aims. We aim to combine the observational information from galaxies at redshifts 5 ≲ z ≲ 10 to constrain their dust emission and theoretically understand the first evolutionary phases of the dust cycle. Methods. Spectral energy distributions (SEDs) are fitted with CIGALE and the physical parameters and their evolution are modelled. From this SED fitting, we built a dust-emission template for this population of galaxies in the reionisation epoch. Results. Our new models explain why some early galaxies are observed and others are not. We follow in time the formation of the first grains by supernovae later destroyed by other supernova blasts and expelled in the circumgalactic and intergalactic media. Conclusions. We find evidence for the first dust grains formed in the universe. But above all, this work underlines the need to collect more data and to develop new facilities to further constrain the dust cycle in galaxies in the reionisation epoch.

scholarly journals An Unbiased CO Survey toward the Northern Region of the Small Magellanic Cloud with the Atacama Compact Array. I. Overview: CO Cloud Distributions

2021 ◽  
Vol 922 (2) ◽  
pp. 171
Author(s):  
Kazuki Tokuda ◽  
Hiroshi Kondo ◽  
Takahiro Ohno ◽  
Ayu Konishi ◽  
Hidetoshi Sano ◽  
...  
Keyword(s):  
Large Scale ◽  
Dust Emission ◽  
Northern Region ◽  
Magellanic Cloud ◽  
Beam Size ◽  
Small Magellanic Cloud ◽  
The Galaxy ◽  
Low Metallicity ◽  
Co Emission ◽  
Compact Array

Abstract We have analyzed the data from a large-scale CO survey toward the northern region of the Small Magellanic Cloud (SMC) obtained with the Atacama Compact Array (ACA) stand-alone mode of ALMA. The primary aim of this study is to comprehensively understand the behavior of CO as an H2 tracer in a low-metallicity environment (Z ∼ 0.2 Z ⊙). The total number of mosaic fields is ∼8000, which results in a field coverage of 0.26 deg2 (∼2.9 ×105 pc2), corresponding to ∼10% of the area of the galaxy. The sensitive ∼2 pc resolution observations reveal the detailed structure of the molecular clouds previously detected in the single-dish NANTEN survey. We have detected a number of compact CO clouds within lower H2 column density (∼1020 cm−2) regions whose angular scale is similar to the ACA beam size. Most of the clouds in this survey also show peak brightness temperature as low as <1 K, which for optically thick CO emission implies an emission size much smaller than the beam size, leading to beam dilution. The comparison between an available estimation of the total molecular material traced by thermal dust emission and the present CO survey demonstrates that more than ∼90% of H2 gas cannot be traced by the low-J CO emission. Our processed data cubes and 2D images are publicly available.

scholarly journals Recurrent Dust Formation by Wolf-Rayet Stars

1991 ◽  
Vol 143 ◽  
pp. 417-420
Author(s):  
P.M. Williams ◽  
K.A. Van Der Hucht ◽  
P.S. Thé ◽  
P. Bouchet ◽  
G. Roberts
Keyword(s):  
Dust Emission ◽  
Infrared Emission ◽  
Circumstellar Dust ◽  
Stellar Winds ◽  
Dust Formation ◽  
Dust Grains

A number of Wolf-Rayet stars show variations of up to a factor of ten in their infrared emission on timescales of months to years while their photospheric luminosities remain unchanged. This can be interpreted in terms of variation in the rates at which dust grains form in their stellar winds. Our data show variable circumstellar dust emission from WR 70 (HD 137603), with an episode of enhanced dust formation in early 1989, and fading of emission by dust formed around WR 48a (in 1979) and WR 19 some time before our first observation in 1988. We consider their relation to WR 140 (HD 193793), which forms dust in its wind for a few months at intervals of 7.94 years.

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