9,039 research outputs found
Advanced Architectures for Astrophysical Supercomputing
Astronomers have come to rely on the increasing performance of computers to
reduce, analyze, simulate and visualize their data. In this environment, faster
computation can mean more science outcomes or the opening up of new parameter
spaces for investigation. If we are to avoid major issues when implementing
codes on advanced architectures, it is important that we have a solid
understanding of our algorithms. A recent addition to the high-performance
computing scene that highlights this point is the graphics processing unit
(GPU). The hardware originally designed for speeding-up graphics rendering in
video games is now achieving speed-ups of in general-purpose
computation -- performance that cannot be ignored. We are using a generalized
approach, based on the analysis of astronomy algorithms, to identify the
optimal problem-types and techniques for taking advantage of both current GPU
hardware and future developments in computing architectures.Comment: 4 pages, 1 figure, to appear in the proceedings of ADASS XIX, Oct 4-8
2009, Sapporo, Japan (ASP Conf. Series
GPU-Based Volume Rendering of Noisy Multi-Spectral Astronomical Data
Traditional analysis techniques may not be sufficient for astronomers to make
the best use of the data sets that current and future instruments, such as the
Square Kilometre Array and its Pathfinders, will produce. By utilizing the
incredible pattern-recognition ability of the human mind, scientific
visualization provides an excellent opportunity for astronomers to gain
valuable new insight and understanding of their data, particularly when used
interactively in 3D. The goal of our work is to establish the feasibility of a
real-time 3D monitoring system for data going into the Australian SKA
Pathfinder archive.
Based on CUDA, an increasingly popular development tool, our work utilizes
the massively parallel architecture of modern graphics processing units (GPUs)
to provide astronomers with an interactive 3D volume rendering for
multi-spectral data sets. Unlike other approaches, we are targeting real time
interactive visualization of datasets larger than GPU memory while giving
special attention to data with low signal to noise ratio - two critical aspects
for astronomy that are missing from most existing scientific visualization
software packages. Our framework enables the astronomer to interact with the
geometrical representation of the data, and to control the volume rendering
process to generate a better representation of their datasets.Comment: 4 pages, 1 figure, to appear in the proceedings of ADASS XIX, Oct 4-8
2009, Sapporo, Japan (ASP Conf. Series
Spotting Radio Transients with the help of GPUs
Exploration of the time-domain radio sky has huge potential for advancing our
knowledge of the dynamic universe. Past surveys have discovered large numbers
of pulsars, rotating radio transients and other transient radio phenomena;
however, they have typically relied upon off-line processing to cope with the
high data and processing rate. This paradigm rules out the possibility of
obtaining high-resolution base-band dumps of significant events or of
performing immediate follow-up observations, limiting analysis power to what
can be gleaned from detection data alone. To overcome this limitation,
real-time processing and detection of transient radio events is required. By
exploiting the significant computing power of modern graphics processing units
(GPUs), we are developing a transient-detection pipeline that runs in real-time
on data from the Parkes radio telescope. In this paper we discuss the
algorithms used in our pipeline, the details of their implementation on the GPU
and the challenges posed by the presence of radio frequency interference.Comment: 4 Pages. To appear in the proceedings of ADASS XXI, ed. P.Ballester
and D.Egret, ASP Conf. Serie
Realtime monitoring for the next generation of radiotelescopes
The forthcoming generation of radiotelescopes pose new and substantial
challenges in terms of system monitoring. Information regarding environmental
conditions, signal connectivity and level, processor utilisation, memory use,
network traffic and even power consumption needs to be collected, displayed in
realtime, and preserved in a permanent database. In this paper, we put forward
the Ganglia monitoring system as a scalable, robust and efficient architecture
that appears well-suited to the data collection aspect of radiotelescope
monitoring, and we discuss approaches to the visual display of the streaming
metric data produced by Ganglia. In particular, we present initial work in the
use of 3-dimensional (3-d) multiplayer game technology for instantaneous status
monitoring and enquiry, and we describe the extensions to this work required
for radiotelescope monitoring.Comment: Submitted to Workshop on Applications of Radio Science (WARS 2008),
accepte
Prospects for Redshifted 21-cm observations of quasar HII regions
The introduction of low-frequency radio arrays over the coming decade is
expected to revolutionize the study of the reionization epoch. Observation of
the contrast in redshifted 21cm emission between a large HII region and the
surrounding neutral IGM will be the simplest and most easily interpreted
signature. We find that an instrument like the planned Mileura Widefield Array
Low-Frequency Demonstrator (LFD) will be able to obtain good signal to noise on
HII regions around the most luminous quasars, and determine some gross
geometric properties, e.g. whether the HII region is spherical or conical. A
hypothetical follow-up instrument with 10 times the collecting area of the LFD
(MWA-5000) will be capable of mapping the detailed geometry of HII regions,
while SKA will be capable of detecting very narrow spectral features as well as
the sharpness of the HII region boundary. The MWA-5000 will discover
serendipitous HII regions in widefield observations. We estimate the number of
HII regions which are expected to be generated by quasars. Assuming a late
reionization at z~6 we find that there should be several tens of quasar HII
regions larger than 4Mpc at z~6-8 per field of view. Identification of HII
regions in forthcoming 21cm surveys can guide a search for bright galaxies in
the middle of these regions. Most of the discovered galaxies would be the
massive hosts of dormant quasars that left behind fossil HII cavities that
persisted long after the quasar emission ended, owing to the long recombination
time of intergalactic hydrogen. A snap-shot survey of candidate HII regions
selected in redshifted 21cm image cubes may prove to be the most efficient
method for finding very high redshift quasars and galaxies.Comment: 14 pages, 8 figures. Submitted to Ap
An HI census of Loose Groups of Galaxies
We present results from our Parkes Multibeam HI survey of 3 loose groups of
galaxies that are analogous to the Local Group. This is a survey of groups
containing only spiral galaxies with mean separations of a few hundred kpc, and
total areas of approximately 1 sq. Mpc; groups similar to our own Local Group.
We present a census of the HI-rich objects in these groups down to an M(HI),
1-sigma sensitivity ~7x10^5 M(sun), as well as the detailed properties of these
detections from follow-up Compact Array observations. We found 7 new HI-rich
members in the 3 groups, all of which have stellar counterparts and are,
therefore, typical dwarf galaxies. The ratio of low-mass to high-mass gas-rich
galaxies in these groups is less than in the Local Group meaning that the
``missing satellite'' problem is not unique. No high-velocity cloud analogs
were found in any of the groups. If HVCs in these groups are the same as in the
Local Group, this implies that HVCs must be located within ~300-400 kpc of the
Milky Way.Comment: 6 pages, to appear in the ASP proceedings of IAU Symposium 217,
"Recycling intergalactic and interstellar matter", eds. Pierre-Alain Duc,
Jonathan Braine, Elias Brink
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