17,147 research outputs found
Identifying Anticyclonic Vortex Features Produced by the Rossby Wave Instability in Protoplanetary Disks
Several nearby protoplanetary disks have been observed to display large scale
crescents in the (sub)millimeter dust continuum emission. One interpretation is
that these structures correspond to anticyclonic vortices generated by the
Rossby wave instability within the gaseous disk. Such vortices have local gas
over-densities and are expected to concentrate dust particles with Stokes
number around unity. This process might catalyze the formation of
planetesimals. Whereas recent observations showed that dust crescent are indeed
regions where millimeter-size particles have abnormally high concentration
relative to the gas and smaller grains, no observations have yet shown that the
gas within the crescent region counter-rotates with respect to the
protoplanetary disk. Here we investigate the detectability of anticyclonic
features through measurement of the line-of-sight component of the gas velocity
obtained with ALMA. We carry out 2D hydrodynamic simulations and 3D radiative
transfer calculation of a protoplanetary disk characterized by a vortex created
by the tidal interaction with a massive planet. As a case study, the disk
parameters are chosen to mimic the IRS 48 system, which has the most prominent
crescent observed to date. We generate synthetic ALMA observations of both the
dust continuum and 12CO emission around the frequency of 345 GHz. We find that
the anticyclonic features of vortex are weak but can be detected if both the
source and the observational setup are properly chosen. We provide a recipe for
maximizing the probability to detect such vortex features and present an
analysis procedure to infer their kinematic properties.Comment: 14 pages, 8 figures, Accepted for publication in Astrophysical
Journa
AstroGrid-D: Grid Technology for Astronomical Science
We present status and results of AstroGrid-D, a joint effort of
astrophysicists and computer scientists to employ grid technology for
scientific applications. AstroGrid-D provides access to a network of
distributed machines with a set of commands as well as software interfaces. It
allows simple use of computer and storage facilities and to schedule or monitor
compute tasks and data management. It is based on the Globus Toolkit middleware
(GT4). Chapter 1 describes the context which led to the demand for advanced
software solutions in Astrophysics, and we state the goals of the project. We
then present characteristic astrophysical applications that have been
implemented on AstroGrid-D in chapter 2. We describe simulations of different
complexity, compute-intensive calculations running on multiple sites, and
advanced applications for specific scientific purposes, such as a connection to
robotic telescopes. We can show from these examples how grid execution improves
e.g. the scientific workflow. Chapter 3 explains the software tools and
services that we adapted or newly developed. Section 3.1 is focused on the
administrative aspects of the infrastructure, to manage users and monitor
activity. Section 3.2 characterises the central components of our architecture:
The AstroGrid-D information service to collect and store metadata, a file
management system, the data management system, and a job manager for automatic
submission of compute tasks. We summarise the successfully established
infrastructure in chapter 4, concluding with our future plans to establish
AstroGrid-D as a platform of modern e-Astronomy.Comment: 14 pages, 12 figures Subjects: data analysis, image processing,
robotic telescopes, simulations, grid. Accepted for publication in New
Astronom
Workshop proceedings: Information Systems for Space Astrophysics in the 21st Century, volume 1
The Astrophysical Information Systems Workshop was one of the three Integrated Technology Planning workshops. Its objectives were to develop an understanding of future mission requirements for information systems, the potential role of technology in meeting these requirements, and the areas in which NASA investment might have the greatest impact. Workshop participants were briefed on the astrophysical mission set with an emphasis on those missions that drive information systems technology, the existing NASA space-science operations infrastructure, and the ongoing and planned NASA information systems technology programs. Program plans and recommendations were prepared in five technical areas: Mission Planning and Operations; Space-Borne Data Processing; Space-to-Earth Communications; Science Data Systems; and Data Analysis, Integration, and Visualization
Miniature exoplanet radial velocity array I: design, commissioning, and early photometric results
The MINiature Exoplanet Radial Velocity Array (MINERVA) is a US-based observational facility dedicated to the discovery and characterization of exoplanets around a nearby sample of bright stars. MINERVA employs a robotic array of four 0.7 m telescopes outfitted for both high-resolution spec- troscopy and photometry, and is designed for completely autonomous operation. The primary science program is a dedicated radial velocity survey and the secondary science objective is to obtain high precision transit light curves. The modular design of the facility and the flexibility of our hardware allows for both science programs to be pursued simultaneously, while the robotic control software provides a robust and efficient means to carry out nightly observations. In this article, we describe the design of MINERVA including major hardware components, software, and science goals. The telescopes and photometry cameras are characterized at our test facility on the Caltech campus in Pasadena, CA, and their on-sky performance is validated. New observations from our test facility demonstrate sub-mmag photometric precision of one of our radial velocity survey targets, and we present new transit observations and fits of WASP-52b—a known hot-Jupiter with an inflated radius and misaligned orbit. The process of relocating the MINERVA hardware to its final destination at the Fred Lawrence Whipple Observatory in southern Arizona has begun, and science operations are expected to commence within 2015
Digital receivers for low-frequency radio telescopes UTR-2, URAN, GURT
This paper describes digital radio astronomical receivers used for decameter
and meter wavelength observations. This paper describes digital radio
astronomical receivers used for decameter and meter wavelength observations.
Since 1998, digital receivers performing on-the-fly dynamic spectrum
calculations or waveform data recording without data loss have been used at the
UTR-2 radio telescope, the URAN VLBI system, and the GURT new generation radio
telescope. Here we detail these receivers developed for operation in the strong
interference environment that prevails in the decameter wavelength range. Data
collected with these receivers allowed us to discover numerous radio
astronomical objects and phenomena at low frequencies, a summary of which is
also presented.Comment: 24 pages, 15 figure
The Robo-AO-2 facility for rapid visible/near-infrared AO imaging and the demonstration of hybrid techniques
We are building a next-generation laser adaptive optics system, Robo-AO-2,
for the UH 2.2-m telescope that will deliver robotic, diffraction-limited
observations at visible and near-infrared wavelengths in unprecedented numbers.
The superior Maunakea observing site, expanded spectral range and rapid
response to high-priority events represent a significant advance over the
prototype. Robo-AO-2 will include a new reconfigurable natural guide star
sensor for exquisite wavefront correction on bright targets and the
demonstration of potentially transformative hybrid AO techniques that promise
to extend the faintness limit on current and future exoplanet adaptive optics
systems.Comment: 15 page
Astrophysics datamining in the classroom: Exploring real data with new software tools and robotic telescopes
Within the efforts to bring frontline interactive astrophysics and astronomy
to the classroom, the Hands on Universe (HOU) developed a set of exercises and
platform using real data obtained by some of the most advanced ground and space
observatories. The backbone of this endeavour is a new free software Web tool -
Such a Lovely Software for Astronomy based on Image J (Salsa J). It is
student-friendly and developed specifically for the HOU project and targets
middle and high schools. It allows students to display, analyze, and explore
professionally obtained astronomical images, while learning concepts on
gravitational dynamics, kinematics, nuclear fusion, electromagnetism. The
continuous evolving set of exercises and tutorials is being completed with real
(professionally obtained) data to download and detailed tutorials. The
flexibility of the Salsa J platform tool enables students and teachers to
extend the exercises with their own observations. The software developed for
the HOU program has been designed to be a multi-platform, multi-lingual
experience for image manipulation and analysis in the classroom. Its design
enables easy implementation of new facilities (extensions and plugins), minimal
in-situ maintenance and flexibility for exercise plugin. Here, we describe some
of the most advanced exercises about astrophysics in the classroom, addressing
particular examples on gravitational dynamics, concepts currently introduced in
most sciences curricula in middle and high schools.Comment: 10 pages, 12 images, submitted to the special theme issue Using
Astronomy and Space Science Research in Physics Courses of the American
Journal of Physic
Shape: A 3D Modeling Tool for Astrophysics
We present a flexible interactive 3D morpho-kinematical modeling application
for astrophysics. Compared to other systems, our application reduces the
restrictions on the physical assumptions, data type and amount that is required
for a reconstruction of an object's morphology. It is one of the first publicly
available tools to apply interactive graphics to astrophysical modeling. The
tool allows astrophysicists to provide a-priori knowledge about the object by
interactively defining 3D structural elements. By direct comparison of model
prediction with observational data, model parameters can then be automatically
optimized to fit the observation. The tool has already been successfully used
in a number of astrophysical research projects.Comment: 13 pages, 11 figures, accepted for publication in the "IEEE
Transactions on Visualization and Computer Graphics
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