scholarly journals Preliminary daytime seeing monitoring at Dome A, Antarctica

2012 ◽  
Vol 8 (S288) ◽  
pp. 296-297
Author(s):  
Chong Pei ◽  
Zhengyangg Li ◽  
Hualin Chen ◽  
Xiangyan Yuan
Keyword(s):  
Large Scale ◽  
Angular Resolution ◽  
Image Motion ◽  
Future Research ◽  
High Angular Resolution ◽  
Optical Parameters ◽  
Site Testing ◽  
Dome A ◽  
Long Period ◽  
Better Than

AbstractSites on Antarctic plateau have unique atmospheric properties that make them better than any mid-latitude sites as observatory locations. From site testing measurements over 4 years on Dome A carried out by the Chinese Center for Antarctic Astronomy, we can reasonably predict that Dome A is as good as or even better than Dome C, which has been proved to be the best astronomical site by now, and suitable for high angular resolution observations. Seeing monitoring is necessary for planning large scale ground-based optical astronomical telescopes. In 2012, the 28th Chinese Antarctic Scientific Expedition carried out preliminary daytime seeing monitoring using a Differential Image Motion Monitor (DIMM) placed at a height of 3.5m. The median seeing was found to be 0.8″. This will be the foundation of future research that obtains comprehensive and long-period monitoring of the site's optical parameters.

scholarly journals SPAN512: A new mid-latitude pulsar survey with the Nançay Radio Telescope

2012 ◽  
Vol 8 (S291) ◽  
pp. 375-377 ◽  
Author(s):  
Gregory Desvignes ◽  
Ismaël Cognard ◽  
David Champion ◽  
Patrick Lazarus ◽  
Patrice Lespagnol ◽  
...  
Keyword(s):  
Radio Telescope ◽  
Large Scale ◽  
High Time ◽  
Frequency Resolution ◽  
Integration Time ◽  
Sensitivity Limit ◽  
Long Period ◽  
Large Bandwidth ◽  
L Band ◽  
Better Than

AbstractWe present an ongoing survey with the Nançay Radio Telescope at L-band. The targeted area is 74° ≲ l < 150° and 3.5° < |b| < 5°. This survey is characterized by a long integration time (18 min), large bandwidth (512 MHz) and high time and frequency resolution (64 μs and 0.5 MHz) giving a nominal sensitivity limit of 0.055 mJy for long period pulsars. This is about 2 times better than the mid-latitude HTRU survey, and is designed to be complementary with current large scale surveys. This survey will be more sensitive to transients (RRATs, intermittent pulsars), distant and faint millisecond pulsars as well as scintillating sources (or any other kind of radio faint sources) than all previous short-integration surveys.

scholarly journals Magnetic Fields in Molecular Clouds

2004 ◽  
Vol 221 ◽  
pp. 83-96
Author(s):  
Tyler L. Bourke ◽  
Alyssa A. Goodman
Keyword(s):  
Star Formation ◽  
Magnetic Fields ◽  
Observational Data ◽  
Observational Studies ◽  
Molecular Clouds ◽  
Large Scale ◽  
Angular Resolution ◽  
Protoplanetary Disks ◽  
High Angular Resolution ◽  
Dense Cores

Magnetic fields are believed to play an important role in the evolution of molecular clouds, from their large scale structure to dense cores, protostellar envelopes, and protoplanetary disks. How important is unclear, and whether magnetic fields are the dominant force driving star formation at any scale is also unclear. In this review we examine the observational data which address these questions, with particular emphasis on high angular resolution observations. Unfortunately the data do not clarify the situation. It is clear that the fields are important, but to what degree we don't yet know. Observations to date have been limited by the sensitivity of available telescopes and instrumentation. In the future ALMA and the SKA in particular should provide great advances in observational studies of magnetic fields, and we discuss which observations are most desirable when they become available.

scholarly journals The Fingerprint of a Galactic Nucleus

2016 ◽  
Vol 11 (S322) ◽  
pp. 257-258
Author(s):  
Francisco Nogueras-Lara ◽  
Rainer Schödel
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Angular Resolution ◽  
Galactic Center ◽  
Fold Increase ◽  
Galactic Centre ◽  
High Angular Resolution ◽  
Imaging Data ◽  
First Results ◽  
Multi Wavelength

AbstractBecause of the unique observational challenges -extreme crowding and extinction- any existing large-scale near-infrared (NIR) imaging data on the Galactic Center (GC) are limited by either one, or a combination, of the following: saturation, lack of sensitivity, too low angular resolution, or lack of multi-wavelength coverage. To overcome this situation, we are currently carrying out a sensitive, 0.2” resolution JHK imaging survey of the Galactic Centre with HAWK-I/VLT. Thanks to holographic imaging, we achieve a similar resolution than with HST/WFC, but can cover also the long NIR, beyond 2 micrometers, which is essential to deal with extinction. Our survey is supported by an ESO Large Programme and will provide photometrically accurate (few percent uncertainty for H < 18 stars), high-angular resolution, NIR data for an area of several 1000 pc2, a more than ten-fold increase compared to the current state of affairs. Here we present an overview and first results.

scholarly journals Fundamental stellar parameters of benchmark stars from CHARA interferometry

2020 ◽  
Vol 640 ◽  
pp. A25
Author(s):  
I. Karovicova ◽  
T. R. White ◽  
T. Nordlander ◽  
L. Casagrande ◽  
M. Ireland ◽  
...  
Keyword(s):  
Angular Resolution ◽  
Local Thermodynamic Equilibrium ◽  
High Angular Resolution ◽  
Fundamental Parameters ◽  
Spectroscopic Observations ◽  
Non Local ◽  
Fundamental Stellar Parameters ◽  
Effective Temperatures ◽  
Limb Darkening ◽  
Better Than

Context. Benchmark stars are crucial as validating standards for current as well as future large stellar surveys of the Milky Way. However, the number of suitable metal-poor benchmark stars is currently limited, owing to the difficulty in determining reliable effective temperatures (Teff) in this regime. Aims. We aim to construct a new set of metal-poor benchmark stars based on reliable interferometric effective temperature determinations and a homogeneous analysis. The aim is to reach a precision of 1% in Teff, as is crucial for sufficiently accurate determinations of the full set of fundamental parameters and abundances for the survey sources. Methods. We observed ten late-type metal-poor dwarfs and giants: HD 2665, HD 6755, HD 6833, HD 103095, HD 122563, HD 127243, HD 140283, HD 175305, HD 221170, and HD 224930. Only three of them (HD 103095, HD 122563, and HD 140283) have previously been used as benchmark stars. For the observations, we used the high-angular-resolution optical interferometric instrument PAVO at the CHARA array. We modelled angular diameters using 3D limb-darkening models and determined effective temperatures directly from the Stefan-Boltzmann relation, with an iterative procedure to interpolate over tables of bolometric corrections. Surface gravities (log(g)) were estimated from comparisons to Dartmouth stellar evolution model tracks. We collected spectroscopic observations from the ELODIE and FIES spectrographs and estimated metallicities ([Fe/H]) from a 1D non-local thermodynamic equilibrium (NLTE) abundance analysis of unblended lines of neutral and singly ionised iron. Results. We inferred Teff to better than 1% for five of the stars (HD 103095, HD 122563, HD 127243, HD 140283, and HD 224930). The effective temperatures of the other five stars are reliable to between 2 and 3%; the higher uncertainty on the Teff for those stars is mainly due to their having a larger uncertainty in the bolometric fluxes. We also determined log(g) and [Fe/H] with median uncertainties of 0.03 dex and 0.09 dex, respectively. Conclusions. This study presents reliable and homogeneous fundamental stellar parameters for ten metal-poor stars that can be adopted as a new set of benchmarks. The parameters are based on our consistent approach of combining interferometric observations, 3D limb-darkening-modelling and spectroscopic observations. The next paper in this series will extend this approach to dwarfs and giants in the metal-rich regime.

scholarly journals E-learning and Blended Learning in Orthodontic Education

2017 ◽  
Vol 7 ◽  
pp. 188-198 ◽  
Author(s):  
Avinash Kumar
Keyword(s):  
Blended Learning ◽  
Large Scale ◽  
Future Research ◽  
Learning Program ◽  
Face To Face ◽  
The Face ◽  
E Learning ◽  
Manual Skills ◽  
Face To Face Learning ◽  
Better Than

The purpose of this article is to evaluate how effective and efficient e-learning and blended learning is when compared with traditional face-to-face learning in orthodontic education. This article also provides a comparison between face-to-face learning, e-learning, and blended learning. An open PubMed literature search was done from 1980 to 2015, and a total of 23 relevant key articles were reviewed. Information emerging from studies in orthodontic education has indicated that e-learning classes are at least as good as and/or better than face-to-face classroom learning. Till date, only one study stated that the face-to-face conventional learning is better than e-learning. Two studies stated that blended approach using both traditional face-to-face learning and e-learning is the best method. In one study, the advantages of e-learning observed in the theoretical fields of orthodontics were not achieved in learning practical procedures for manual skills. Few studies found improvements in the efficiency of learning with e-learning program. Studies performed through questionnaires showed that student’s attitude and acceptance toward the use of e-learning was positive and favorable; however, blended learning was always rated high. Future research should be based on experiences of both faculty and student on a large scale for implementation of e-learning and blended learning in academic institutions. There is also need to provide professional development for faculty who will be teaching both in the physical and virtual environments.

scholarly journals High Angular Resolution Mid-IR Astronomy at Concordia

2005 ◽  
Vol 13 ◽  
pp. 964-964
Author(s):  
Marco Ferrari-Toniolo
Keyword(s):  
Large Scale ◽  
Angular Resolution ◽  
High Sensitivity ◽  
Young Star ◽  
High Angular Resolution ◽  
Star Forming ◽  
Infrared Telescope ◽  
Dry Conditions ◽  
Drift Scan ◽  
Tracking Time

If we concentrate our attention on the study and the evolution of star forming processes rather than on the large scale structure, from the recent use of Large Telescopes in this context there are many examples of great interest. These include the study of the early phases of aggregation of matter (stellar and planet formation), and the late phases of disaggregation during stellar evolution. In Fig 1, a spectacular example is shown of a high resolution image of an edge-on circumstellar disk of a young star (HR4796A), with respect to previous less resolved information (C.Telesco et al, Proc SPIE 4834, 101, 2002). A recent hypothesis of a Large Infrared Telescope called GTA (Grande Telescopio Antartico) has been proposed to the PNRA (Italian Plan for Antarctic Researches). This will require the following characteristics: high angular resolution in the mid-IR domain (large aperture); very high sensitivity (mainly due to the cold, dry conditions of the site); extreme simplicity in design and operational modes. The telescope will be a survey instrument and will be used almost without human intervention. The project examines the construction of a third tower at Dome C with the telescope configured to work in quasi-drift-scan without moving the enclosure and with a limited tracking time. In Fig 1, a sketch of the tower hosting the telescope is shown (M.F-T. et al, Proc SPIE 4836, 165, 2002). A study will be developed to determine the optimum configurations for observing in different bands, from the optical to the sub-mm range, with a refurbishment of the telescope and instrumentation during the summer break.

scholarly journals Active gas features in three HSC-SSP CAMIRA clusters revealed by high angular resolution analysis of MUSTANG-2 SZE and XXL X-ray observations

2020 ◽  
Vol 501 (2) ◽  
pp. 1701-1732
Author(s):  
Nobuhiro Okabe ◽  
Simon Dicker ◽  
Dominique Eckert ◽  
Tony Mroczkowski ◽  
Fabio Gastaldello ◽  
...  
Keyword(s):  
Large Scale ◽  
Angular Resolution ◽  
Major Axis ◽  
High Angular Resolution ◽  
X Ray ◽  
Spatially Resolved ◽  
Sunyaev Zel'dovich Effect ◽  
Major Merger ◽  
Resolution Analysis ◽  
A Minor

ABSTRACT We present results from simultaneous modelling of high angular resolution GBT/MUSTANG-2 90 GHz Sunyaev–Zel’dovich effect (SZE) measurements and XMM-XXL X-ray images of three rich galaxy clusters selected from the HSC-SSP Survey. The combination of high angular resolution SZE and X-ray imaging enables a spatially resolved multicomponent analysis, which is crucial to understand complex distributions of cluster gas properties. The targeted clusters have similar optical richnesses and redshifts, but exhibit different dynamical states in their member galaxy distributions: a single-peaked cluster, a double-peaked cluster, and a cluster belonging to a supercluster. A large-scale residual pattern in both regular Compton-parameter y and X-ray surface brightness distributions is found in the single-peaked cluster, indicating a sloshing mode. The double-peaked cluster shows an X-ray remnant cool core between two SZE peaks associated with galaxy concentrations. The temperatures of the two peaks reach ∼20–30 keV in contrast to the cool core component of ∼2 keV, indicating a violent merger. The main SZE signal for the supercluster is elongated along a direction perpendicular to the major axis of the X-ray core, suggesting a minor merger before core passage. The SX and y distributions are thus perturbed at some level, regardless of the optical properties. We find that the integrated Compton y parameter and the temperature for the major merger are boosted from those expected by the weak-lensing mass and those for the other two clusters show no significant deviations, which is consistent with predictions of numerical simulations.

scholarly journals CHIMPS: physical properties of molecular clumps across the inner Galaxy

2019 ◽  
Vol 632 ◽  
pp. A58 ◽  
Author(s):  
A. J. Rigby ◽  
T. J. T. Moore ◽  
D. J. Eden ◽  
J. S. Urquhart ◽  
S. E. Ragan ◽  
...  
Keyword(s):  
Physical Properties ◽  
Molecular Clouds ◽  
Large Scale ◽  
Angular Resolution ◽  
Galactic Plane ◽  
Continuum Emission ◽  
High Angular Resolution ◽  
Molecular Gas ◽  
Excitation Temperature ◽  
Galactocentric Distance

The latest generation of high-angular-resolution unbiased Galactic plane surveys in molecular-gas tracers are enabling the interiors of molecular clouds to be studied across a range of environments. The CO Heterodyne Inner Milky Way Plane Survey (CHIMPS) simultaneously mapped a sector of the inner Galactic plane, within 27.8° ≲ ℓ ≲ 46.2° and |b|≤ 0°.5, in 13CO (3–2) and C18O (3–2) at an angular resolution of 15 arcsec. The combination of the CHIMPS data with 12CO (3–2) data from the CO High Resolution Survey (COHRS) has enabled us to perform a voxel-by-voxel local-thermodynamic-equilibrium (LTE) analysis, determining the excitation temperature, optical depth, and column density of 13CO at each ℓ, b, v position. Distances to discrete sources identified by FELLWALKER in the 13CO (3–2) emission maps were determined, allowing the calculation of numerous physical properties of the sources, and we present the first source catalogues in this paper. We find that, in terms of size and density, the CHIMPS sources represent an intermediate population between large-scale molecular clouds identified by CO and dense clumps seen in thermal dust continuum emission, and therefore represent the bulk transition from the diffuse to the dense phase of molecular gas. We do not find any significant systematic variations in the masses, column densities, virial parameters, mean excitation temperature, or the turbulent pressure over the range of Galactocentric distance probed, but we do find a shallow increase in the mean volume density with increasing Galactocentric distance. We find that inter-arm clumps have significantly narrower linewidths, and lower virial parameters and excitation temperatures than clumps located in spiral arms. When considering the most reliable distance-limited subsamples, the largest variations occur on the clump-to-clump scale, echoing similar recent studies that suggest that the star-forming process is largely insensitive to the Galactic-scale environment, at least within the inner disc.

scholarly journals The dynamically young outflow of the Class 0 protostar Cha-MMS1

2020 ◽  
Vol 633 ◽  
pp. A126 ◽  
Author(s):  
L. A. Busch ◽  
A. Belloche ◽  
S. Cabrit ◽  
P. Hennebelle ◽  
B. Commerçon
Keyword(s):  
Magnetic Field ◽  
Chemical Composition ◽  
Large Scale ◽  
Angular Resolution ◽  
Continuum Emission ◽  
High Angular Resolution ◽  
Upper Limit ◽  
Large Scale Magnetic Field ◽  
Full Power ◽  
Magnetohydrodynamic Simulations

Context. On the basis of its low luminosity, its chemical composition, and the absence of a large-scale outflow, the dense core Cha-MMS1 located in the Chamaeleon I molecular cloud, was proposed a decade ago as a candidate for a first hydrostatic core (FHSC). Aims. Our goal is to test this hypothesis by searching for a slow, compact outflow driven by Cha-MMS1 that would match the predictions of magnetohydrodynamic simulations for this short phase of star formation. Methods. We used the Atacama Large Millimetre/submillimetre Array to map Cha-MMS1 at high angular resolution in CO 3–2 and 13CO 3–2 as well as in continuum emission. Results. We report the detection of a bipolar outflow emanating from the central core, along a (projected) direction roughly parallel to the filament in which Cha-MMS1 is embedded and perpendicular to the large-scale magnetic field. The morphology of the outflow indicates that its axis lies close to the plane of the sky. We measure velocities corrected for inclination of more than 90 km s−1, which is clearly incompatible with the expected properties of an FHSC outflow. Several properties of the outflow are determined and compared to previous studies of Class 0 and Class I protostars. The outflow of Cha-MMS1 has a much smaller momentum force than the outflows of other Class 0 protostars. In addition, we find a dynamical age of 200–3000 yr indicating that Cha-MMS1 might be one of the youngest ever observed Class 0 protostars. While the existence of the outflow suggests the presence of a disk, no disk is detected in continuum emission and we derive an upper limit of 55 au to its radius. Conclusions. We conclude that Cha-MMS1 has already gone through the FHSC phase and is a young Class 0 protostar, but it has not yet brought its outflow to full power.

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