scholarly journals High spatial resolution multiwavelength observations of star and planet formation

2001 ◽  
Vol 205 ◽  
pp. 236-243
Author(s):  
Mark J. McCaughrean
Keyword(s):  
Spatial Resolution ◽  
Planet Formation ◽  
Angular Resolution ◽  
High Spatial Resolution ◽  
High Angular Resolution ◽  
Multiwavelength Observations

We discuss the importance of multiwavelength (optical, infrared, millimetre, and radio), high angular resolution (arcsec to subarcsec) observations in studying star and planet formation. We provide a few illustrative examples, and briefly discuss how future observational facilities will allow a yet more detailed view of the important processes at work.

scholarly journals Resolving the mass loss from red supergiants by high angular resolution

2016 ◽  
Vol 12 (S329) ◽  
pp. 97-103
Author(s):  
Keiichi Ohnaka
Keyword(s):  
Mass Loss ◽  
Spatial Resolution ◽  
Angular Resolution ◽  
High Spatial Resolution ◽  
Spatial Scales ◽  
High Angular Resolution ◽  
Circumstellar Envelope ◽  
Long Baseline ◽  
Red Supergiants ◽  
Late Stages

AbstractDespite its importance on late stages of the evolution of massive stars, the mass loss from red supergiants (RSGs) is a long-standing problem. To tackle this problem, it is essential to observe the wind acceleration region close to the star with high spatial resolution. While the mass loss from RSGs is often assumed to be spherically symmetric with a monotonically accelerating wind, there is mounting observational evidence that the reality is much more complex. I review the recent progress in high spatial resolution observations of RSGs, encompassing from the circumstellar envelope on rather large spatial scales (~100 stellar radii) to milliarcsecond-resolution aperture-synthesis imaging of the surface and the atmosphere of RSGs with optical and infrared long-baseline interferometers.

scholarly journals Interpreting high spatial resolution line observations of planet-forming disks with gaps and rings: the case of HD 163296

2020 ◽  
Vol 642 ◽  
pp. A165
Author(s):  
Ch. Rab ◽  
I. Kamp ◽  
C. Dominik ◽  
C. Ginski ◽  
G. A. Muro-Arena ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Line Emission ◽  
High Angular Resolution ◽  
Back Side ◽  
Gas Temperature ◽  
Disk Model ◽  
Gas Density ◽  
The Impact ◽  
Gas Properties

Context. Spatially resolved continuum observations of planet-forming disks show prominent ring and gap structures in their dust distribution. However, the picture from gas observations is much less clear and constraints on the radial gas density structure (i.e. gas gaps) remain rare and uncertain. Aims. We want to investigate the importance of thermo-chemical processes for the interpretation of high-spatial-resolution gas observations of planet-forming disks and their impact on the derived gas properties. Methods. We applied the radiation thermo-chemical disk code PRODIMO (PROtoplanetary DIsk MOdel) to model the dust and gas disk of HD 163296 self-consistently, using the DSHARP (Disk Substructure at High Angular Resolution) gas and dust observations. With this model we investigated the impact of dust gaps and gas gaps on the observables and the derived gas properties, considering chemistry, and heating and cooling processes. Results. We find distinct peaks in the radial line intensity profiles of the CO line data of HD 163296 at the location of the dust gaps. Our model indicates that those peaks are not only a consequence of a gas temperature increase within the gaps but are mainly caused by the absorption of line emission from the back side of the disk by the dust rings. For two of the three prominent dust gaps in HD 163296, we find that thermo-chemical effects are negligible for deriving density gradients via measurements of the rotation velocity. However, for the gap with the highest dust depletion, the temperature gradient can be dominant and needs to be considered to derive accurate gas density profiles. Conclusions. Self-consistent gas and dust thermo-chemical modelling in combination with high-quality observations of multiple molecules are necessary to accurately derive gas gap depths and shapes. This is crucial to determine the origin of gaps and rings in planet-forming disks and to improve the mass estimates of forming planets if they are the cause of the gap.

scholarly journals Prospects for High Angular Resolution Instrumentation at Millimeter and Submillimeter Wavelengths

2001 ◽  
Vol 205 ◽  
pp. 432-437
Author(s):  
Karl M. Menten
Keyword(s):  
Spatial Resolution ◽  
Angular Resolution ◽  
Diffraction Limit ◽  
High Angular Resolution ◽  
Submillimeter Wavelength ◽  
Millimeter Astronomy ◽  
Short Summary ◽  
Submillimeter Wavelengths ◽  
Millimeter And Submillimeter Wavelengths ◽  
Infrared Telescopes

Millimeter- and submillimeter wavelength interferometry is a powerful technique allowing imaging of dust and molecules in a multitude of astronomical environments. With the arrival of the Atacama Large Millimeter Array (ALMA), such studies will be possible with unprecedented sensitivity and a spatial resolution similar to the diffraction limit of large optical/infrared telescopes. In this paper, we mention a few aspects of (sub) millimeter astronomy and provide a short summary of ALMA's capabilities.

scholarly journals Radio Interferometry Observations of the Hallmarks of Planet Formation

2013 ◽  
Vol 8 (S299) ◽  
pp. 80-89
Author(s):  
Sean M. Andrews
Keyword(s):  
Planet Formation ◽  
Angular Resolution ◽  
Planetary System ◽  
Planetary Systems ◽  
Protoplanetary Disks ◽  
Circumstellar Disks ◽  
High Angular Resolution ◽  
Radio Interferometry ◽  
New Directions ◽  
And Migration

AbstractSome of the fundamental processes involved in the evolution of circumstellar disks and the assembly of planetary systems are just now becoming accessible to astronomical observations. The new promise of observational work in the field of planet formation makes for a very dynamic research scenario, which is certain to be amplified in the coming years as the revolutionary Atacama Large Millimeter/submillimeter Array (ALMA) facility ramps up to full operations. To highlight the new directions being explored in these fields, this brief review will describe how high angular resolution measurements at millimeter/radio wavelengths are being used to study several crucial aspects of the formation and early evolution of planetary systems, including: the gas and dust structures of protoplanetary disks, the growth and migration of disk solids, and the interactions between a young planetary system and its natal, gas-rich disk.

scholarly journals The Future of High Angular Resolution Star and Planet Formation Science in the Optical/Infrared

2004 ◽  
Vol 221 ◽  
pp. 471-479
Author(s):  
Lynne A. Hillenbrand
Keyword(s):  
Planet Formation ◽  
Angular Resolution ◽  
Time Frame ◽  
High Angular Resolution ◽  
The Future

This presentation summarizes how some of the most pressing questions in the field of star and planet formation can be addressed by high angular resolution optical/infrared capabilities, and how many of these capabilities will in fact be available with realization of the space and ground facilities currently being planned for the 2005-2020 time frame.

Formation and Evolution of Protoplanetary Disks: Observations and Modeling of Jets, Disks, and Disk Substructures

2018 ◽  
Vol 14 (S345) ◽  
pp. 96-101
Author(s):  
Laura M. Pérez
Keyword(s):  
Planet Formation ◽  
Angular Resolution ◽  
Planetary System ◽  
Protoplanetary Disks ◽  
Solid Particles ◽  
High Angular Resolution ◽  
Rapid Progress ◽  
Disk Evolution ◽  
Formation And Evolution ◽  
Dusty Disks

AbstractPlanet formation takes place in the gaseous and dusty disks that surround young stars, known as protoplanetary disks. With the advent of sensitive observations and together with developments in theory, our field is making rapid progress in understanding how the evolution of protoplanetary disks takes place, from its inception to the end result of a fully-formed planetary system. In this review, I discuss how observations that trace both the dust and gas components of these systems inform us about their evolution, mass budget, and chemistry. Particularly, the process of disk evolution and planet formation will leave an imprint on the distribution of solid particles at different locations in a protoplanetary disk, and I focus on recent observational results at high angular resolution in the sub-millimeter regime, which have revealed a variety of substructures present in these objects.

scholarly journals The gas structure of the HD 163296 planet-forming disk - gas gaps or not?

2019 ◽  
Vol 15 (S350) ◽  
pp. 445-447
Author(s):  
C. Rab ◽  
G. A. Muro-Arena ◽  
I. Kamp ◽  
C. Dominik ◽  
L. B. F. M. Waters ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Planet Formation ◽  
High Spatial Resolution ◽  
Young Star ◽  
Intensity Profile ◽  
Preliminary Results ◽  
Gas Chemistry ◽  
Self Consistent ◽  
First Results ◽  
The Impact

AbstractHD 163296 is a young star surrounded by a planet-forming disk that shows clear signatures of dust gaps and rings; likely an indication of ongoing planet formation. We use the radiation thermochemical disk code ProDiMo to investigate the impact of dust/gas gaps on the temperature, chemistry and observables. Furthermore, we model high spatial resolution gas and dust observation of HD 163296 (ALMA/DSHARP). Our first results indicate that features in the observed radial intensity profile of the 12CO line are a consequence of the dust gaps and do not require gas depletion. Those preliminary results indicate that self-consistent modelling of the gas (chemistry, heating/cooling) and dust is necessary to accurately infer the degree of gas depletion within dust gaps. Such information is crucial to understand the processes that generate the disk substructure and their relation to planet formation.

scholarly journals Spatial versus angular resolution for tractography-assisted planning of deep brain stimulation

2019 ◽  
Author(s):  
Luka C. Liebrand ◽  
Guido A. van Wingen ◽  
Frans M. Vos ◽  
Damiaan Denys ◽  
Matthan W.A. Caan
Keyword(s):  
Deep Brain Stimulation ◽  
Spatial Resolution ◽  
Brain Stimulation ◽  
Diffusion Mri ◽  
Angular Resolution ◽  
Internal Capsule ◽  
High Angular Resolution ◽  
Scanning Time ◽  
Mri Protocol ◽  
Deep Brain

AbstractGiven the restricted total scanning time for clinical neuroimaging, it is unclear whether clinical diffusion MRI protocols would benefit more from higher spatial resolution or higher angular resolution. In this work, we investigated the relative benefit of improving spatial or angular resolution in diffusion MRI to separate two parallel running white matter tracts that are targets for deep brain stimulation: the anterior thalamic radiation and the supero-lateral branch of the medial forebrain bundle. Both these tracts are situated in the ventral anterior limb of the internal capsule, and recent studies suggest that targeting a specific tract could improve treatment efficacy. Therefore, we scanned 19 healthy volunteers at 3T and 7T according to three diffusion MRI protocols with respectively standard clinical settings, increased spatial resolution of 1.4 mm, and increased angular resolution (64 additional gradient directions at b=2200s/mm2). We performed probabilistic tractography for all protocols and quantified the separability of both tracts. The higher spatial resolution protocol improved separability by 41% with respect to the clinical standard, presumably due to decreased partial voluming. The higher angular resolution protocol resulted in increased apparent tract volumes and overlap, which is disadvantageous for application in precise treatment planning. We thus recommend to increase the spatial resolution for deep brain stimulation planning to 1.4 mm while maintaining angular resolution. This recommendation complements the general advice to aim for high angular resolution to resolve crossing fibers, confirming that the specific application and anatomical considerations are leading in clinical diffusion MRI protocol optimization.

scholarly journals Resolution and b value dependent Structural Connectome in ex vivo Mouse Brain

2022 ◽  
Author(s):  
Stephanie Crater ◽  
Surendra Maharjan ◽  
Yi Qi ◽  
Qi Zhao ◽  
Gary Cofer ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Mouse Brain ◽  
Diffusion Mri ◽  
Angular Resolution ◽  
Ex Vivo ◽  
B Value ◽  
High Angular Resolution ◽  
Preclinical Studies ◽  
High Quality ◽  
Structural Connectome

Diffusion magnetic resonance imaging has been widely used in both clinical and preclinical studies to characterize tissue microstructure and structural connectivity. The diffusion MRI protocol for the Human Connectome Project (HCP) has been developed and optimized to obtain high-quality, high-resolution diffusion MRI (dMRI) datasets. However, such efforts have not been fully explored in preclinical studies, especially for rodents. In this study, high quality dMRI datasets of mouse brains were acquired at 9.4T system from two vendors. In particular, we acquired a high-spatial resolution dMRI dataset (25 um isotropic with 126 diffusion encoding directions), which we believe to be the highest spatial resolution yet obtained; and a high-angular resolution dMRI dataset (50 um isotropic with 384 diffusion encoding directions), which we believe to be the highest angular resolution compared to the dMRI datasets at the microscopic resolution. We systematically investigated the effects of three important parameters that affect the final outcome of the connectome: b value (1000 s/mm2 to 8000 s/mm2), angular resolution (10 to 126), and spatial resolution (25 um to 200 um). The stability of tractography and connectome increase with the angular resolution, where more than 50 angles are necessary to achieve consistent results. The connectome and quantitative parameters derived from graph theory exhibit a linear relationship to the b value (R2 > 0.99); a single-shell acquisition with b value of 3000 s/mm2 shows comparable results to the multi-shell high angular resolution dataset. The dice coefficient decreases and both false positive rate and false negative rate gradually increase with coarser spatial resolution. Our study provides guidelines and foundations for exploration of tradeoffs among acquisition parameters for the structural connectome in ex vivo mouse brain.

Small-Angle Electron Scattering (SAES) of Polymers

1985 ◽  
Vol 43 ◽  
pp. 78-79
Author(s):  
Ralph Oralor ◽  
Pamela Lloyd ◽  
Satish Kumar ◽  
W. W. Adams
Keyword(s):  
Electron Scattering ◽  
Small Angle ◽  
Angular Resolution ◽  
Structural Features ◽  
Objective Lens ◽  
High Angular Resolution ◽  
Push Button ◽  
First Case ◽  
Diffraction Mode ◽  
Very High

Small angle electron scattering (SAES) has been used to study structural features of up to several thousand angstroms in polymers, as well as in metals. SAES may be done either in (a) long camera mode by switching off the objective lens current or in (b) selected area diffraction mode. In the first case very high camera lengths (up to 7Ø meters on JEOL 1Ø ØCX) and high angular resolution can be obtained, while in the second case smaller camera lengths (approximately up to 3.6 meters on JEOL 1Ø ØCX) and lower angular resolution is obtainable. We conducted our SAES studies on JEOL 1ØØCX which can be switched to either mode with a push button as a standard feature.

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