scholarly journals Ubiquitous Disks in AGN

1997 ◽  
Vol 163 ◽  
pp. 152-161
Author(s):  
Gary D. Schmidt
Keyword(s):  
Optical Imaging ◽  
Entire Range ◽  
Recent Progress ◽  
Angular Resolution ◽  
High Angular Resolution ◽  
Great Success ◽  
Nuclear Activity

AbstractDisk-like structures have been inferred to exist in the nuclei of galaxies over the entire range in nuclear activity. These form the essence of the Unified Scheme, which has had great success in accounting for AGN of a wide variety of perceived types. Recent progress along this front is summarized, including new polarimetric results, high-angular resolution optical imaging, and interferometry at radio wavelengths.

scholarly journals Infall in Protostellar Envelopes

2004 ◽  
Vol 221 ◽  
pp. 75-82
Author(s):  
Nagayoshi Ohashi
Keyword(s):  
Observational Studies ◽  
Recent Progress ◽  
Angular Resolution ◽  
Protoplanetary Disks ◽  
Great Emphasis ◽  
High Angular Resolution ◽  
Compact Disks

We summarize recent progress of observational studies of infall in protostellar envelopes, with great emphasis on results obtained using millimeter and submillimeter interferometers. Interferometric observations allow us to spatially resolve kinematical structures of protostellar envelopes, enabling us to detect infalling motions in the envelope directly. High angular resolution observations of infalling envelopes having compact disks sufficiently bright in continuum show inverse P-Cygni profiles, which are the least ambiguous evidence for infall. Observations of infalling envelopes using the Submillimeter Array (SMA) may allow us to study the innermost infalling envelopes, where infalling motions most probably transform to Keplerian motions, leading to formation of Keplerian or protoplanetary disks around protostars.

Direct Optical Imaging of Be Disks

2000 ◽  
Vol 175 ◽  
pp. 129-140
Author(s):  
Philippe Stee
Keyword(s):  
Optical Imaging ◽  
Spectral Resolution ◽  
Role Models ◽  
Angular Resolution ◽  
High Spectral Resolution ◽  
High Angular Resolution ◽  
Be Stars ◽  
Hot Stars ◽  
Time Consumption ◽  
Circumstellar Environment

AbstractInterferometry in the visible now provides milliarcsecond spatial resolution and thus can be used for studying the circumstellar environment of Be stars. In this review I will first introduce the two basic quantities that an interferometer can access: the modulus and the phase of the visibility. I will illustrate how these two quantities can be used to understand the physics of Be disks through recent results from the VLA, the MkII and the GI2T interferometers. I will insist on the importance and the potential of coupling high angular resolution with high spectral resolution to the study of Be disks. Since the possibility of direct optical imaging of Be disks will be limited due to complexity and time consumption, I will present the role models can play in interpreting high angular resolution observations when direct imaging become difficult. Finally I will draw up a list of challenging objectives for the next generation of synthetic arrays (GI2T/REGAIN, Keck, ST3, VLTI) which will bring new understanding of active hot stars physics.

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.

Large-angle convergent-beam electron-diffraction study of coherent precipitates and decorated dislocations

1996 ◽  
Vol 54 ◽  
pp. 1002-1004
Author(s):  
J.M.K. Wiezorek ◽  
H.L. Fraser
Keyword(s):  
Electron Diffraction ◽  
Angular Resolution ◽  
Large Angle ◽  
Electron Diffraction Study ◽  
Convergent Beam Electron Diffraction ◽  
Crystal Defects ◽  
High Angular Resolution ◽  
Beam Electron ◽  
Diffraction Plane ◽  
Convergent Beam

Conventional methods of convergent beam electron diffraction (CBED) use a fully converged probe focused on the specimen in the object plane resulting in the formation of a CBED pattern in the diffraction plane. Large angle CBED (LACBED) uses a converged but defocused probe resulting in the formation of ‘shadow images’ of the illuminated sample area in the diffraction plane. Hence, low-spatial resolution image information and high-angular resolution diffraction information are superimposed in LACBED patterns which enables the simultaneous observation of crystal defects and their effect on the diffraction pattern. In recent years LACBED has been used successfully for the investigation of a variety of crystal defects, such as stacking faults, interfaces and dislocations. In this paper the contrast from coherent precipitates and decorated dislocations in LACBED patterns has been investigated. Computer simulated LACBED contrast from decorated dislocations and coherent precipitates is compared with experimental observations.

Binary Cepheids From High-Angular Resolution

2015 ◽  
Vol 71-72 ◽  
pp. 187-188
Author(s):  
A. Gallenne ◽  
A. Mérand ◽  
P. Kervella
Keyword(s):  
Angular Resolution ◽  
High Angular Resolution

350 Micron Continuum Imaging of the Orion A Molecular Cloud with the Submillimeter High Angular Resolution Camera

1998 ◽  
Vol 509 (1) ◽  
pp. 299-308 ◽  
Author(s):  
D. C. Lis ◽  
E. Serabyn ◽  
Jocelyn Keene ◽  
C. D. Dowell ◽  
D. J. Benford ◽  
...  
Keyword(s):  
Molecular Cloud ◽  
Angular Resolution ◽  
High Angular Resolution

scholarly journals Hunting for intermediate-mass black holes in globular clusters: an astrometric study of NGC 6441

2021 ◽  
Vol 503 (1) ◽  
pp. 1490-1506
Author(s):  
Maximilian Häberle ◽  
Mattia Libralato ◽  
Andrea Bellini ◽  
Laura L Watkins ◽  
Jörg-Uwe Pott ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Velocity Dispersion ◽  
Angular Resolution ◽  
Hubble Space Telescope ◽  
High Mass ◽  
High Angular Resolution ◽  
Stellar Kinematics ◽  
Intermediate Mass ◽  
The Core ◽  
Large Telescopes

ABSTRACT We present an astrometric study of the proper motions (PMs) in the core of the globular cluster NGC 6441. The core of this cluster has a high density and observations with current instrumentation are very challenging. We combine ground-based, high-angular-resolution NACO@VLT images with Hubble Space Telescope ACS/HRC data and measure PMs with a temporal baseline of 15 yr for about 1400 stars in the centremost 15 arcsec of the cluster. We reach a PM precision of ∼30 µas yr−1 for bright, well-measured stars. Our results for the velocity dispersion are in good agreement with other studies and extend already existing analyses of the stellar kinematics of NGC 6441 to its centremost region never probed before. In the innermost arcsecond of the cluster, we measure a velocity dispersion of (19.1 ± 2.0) km s−1 for evolved stars. Because of its high mass, NGC 6441 is a promising candidate for harbouring an intermediate-mass black hole (IMBH). We combine our measurements with additional data from the literature and compute dynamical models of the cluster. We find an upper limit of $M_{\rm IMBH} \lt 1.32 \times 10^4\, \textrm{M}_\odot$ but we can neither confirm nor rule out its presence. We also refine the dynamical distance of the cluster to $12.74^{+0.16}_{-0.15}$ kpc. Although the hunt for an IMBH in NGC 6441 is not yet concluded, our results show how future observations with extremely large telescopes will benefit from the long temporal baseline offered by existing high-angular-resolution data.

Zooming into the complex dusty envelopes of C-rich AGB stars

2018 ◽  
Vol 14 (S343) ◽  
pp. 456-457
Author(s):  
Foteini Lykou ◽  
Josef Hron ◽  
Daniela Klotz
Keyword(s):  
Temperature Distribution ◽  
Near Infrared ◽  
Angular Resolution ◽  
High Angular Resolution ◽  
Dust Formation ◽  
Agb Stars ◽  
Circumstellar Envelopes ◽  
Recent Advances ◽  
Multi Wavelength

AbstractRecent advances in high-angular resolution instruments (VLT and VLTI, ALMA) have enabled us to delve deep into the circumstellar envelopes of AGB stars from the optical to the sub-mm wavelengths, thus allowing us to study in detail the gas and dust formation zones (e.g., their geometry, chemistry and kinematics). This work focuses on four (4) C-rich AGB stars observed with a high-angular resolution technique in the near-infrared: a multi-wavelength tomographic study of the dusty layers of the circumstellar envelopes of these C-rich stars, i.e. the variations in the morphology and temperature distribution.

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