Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.atnf.csiro.au/people/Matthew.Whiting/ASKAPsimSL1/README Дата изменения: Tue May 3 05:32:19 2011 Дата индексирования: Tue Oct 2 16:54:28 2012 Кодировка: Поисковые слова: http www.astronomy.ru forum index.php topic 4644.0.html

This ASKAP data release includes a spectral-line simulation. This was created in the following way:
* The SKADS S3-SAX simulation (Obreschkow et al 2009) was used as the source catalogue from which a
sky model image was created.
* This sky model was used as input into a telescope simulation. This simulation featured:
o The 2km core of the ASKAP configuration (30 antennas only)
o The effect of the phased-array feed was simulated by using 32 idealised beams, spaced in a
rectangular grid 1 degree apart (the arrangement is a 6x6 square, without the corners).
o The spectral setup had 1024 channels of 92.5kHz width (5x the width of the ASKAP fine channels),
from 1327.39 to 1422.0175 MHz.
o The total integration time was 8 hrs, made up of 5sec integrations.
o The simulating was done separately for each channel.
o The total size of the measurement sets containing the visibilities is 2.3TB - we are not
making these available!
* The image cube was created with the prototype ASKAPsoft imager code. The cube presented is
the dirty image, without any preconditioning. The imaging is also done separately for each
channel, with the dirty images then being merged to form the complete cube.

All processing was done on the NCI National Facility machine vayu.

24/3/2010:
We have included information about the sources in the sky model. There is a new model cube that has the same input
catalogue, but reproduced at the same pixel scale as the image, and smoothed with a 30 arcsec beam. We provde subsets
of this that match the subsets of the dirty cube.

We also provide a catalogue of sources extracted from that image (using the ASKAPsoft version of the Duchamp
source finder).

Finally, we also provide the SKADS input catalogue used to create the models. Refer to Obreschkow et al (2009) or
http://s-cubed.physics.ox.ac.uk/s3-sax for details on the information therein.
(An earlier version of this file had the original SKADS positions, which were centred at (RA,DEC)=(0,0).
This has been corrected to the position of the simulated field.)


The data is available on the local ATNF computer system, at giant:/DATA/DELPHINUS_2/whi550/ASKAPsimulations/SpectralLine/Feb2010.
As all survey science teams have ATNF members, this was judged as the easiest way to distribute the data. Those requiring
access to the data who do not have an ATNF account should contact the ASKAP Project Scientists for assistance.

Please Note: The continuum simulation is currently delayed while we investigate artifacts arising in the imaging.
This is leading to improvements in our software, particularly for dealing with such large data sets.
It is possible that such artifacts are present in the spectral cube, although the sources here are
much fainter and so less likely to show artifacts. Whether the fluxes of sources are correct has not
yet been checked exhaustively, but we are providing this cube for people to get experience in dealing
with the large data sizes.

We of course would welcome any feedback from your investigations: please use the ASKAP redmine site
or contact one of the ASKAP Project Scientists.

Contents of directory:

README : This file
ASKAPsim_Spectralline_Mar2010 : 2560x2560x1024 spectral cube over full field and full spectral range. CASA format only
ASKAPsim_Spectralline_Mar2010_fullfieldsubset : 2560x2560x41 spectral cube, full spatial field, 41 channels. CASA & FITS formats
ASKAPsim_Spectralline_Mar2010_fullspectrumsubset : 512x512x1024 spectral cube, full spectral range with 1.4deg FoV. CASA & FITS formats
ASKAPsim_SpectrallineModel_Mar2010 : 4096x4096x1024 spectral cube, holding the input sky model
ASKAPsim_SpectrallineModel_Mar2010_matching : 2560x2560x1024 sky model (same pixel scale as dirty cube, smoothed with 30arcsec beam) CASA format only
ASKAPsim_SpectrallineModel_Mar2010_matching_fullfieldsubset : 2560x2560x41 subset of matching sky model. CASA & FITS formats
ASKAPsim_SpectrallineModel_Mar2010_matching_fullspectrumsubset : 512x512x1024 subset of matching sky model. CASA & FITS formats
ASKAPsim_SpectrallineModel_Mar2010_matching_sourcelist.dat : List of sources found in matching sky model, to peak flux of 1.e-4 Jy/beam
ASKAPsim_SpectrallineModel_Mar2010_input_catalogue.dat : Input catalogue used, in SKADS S3-SAX format
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Matthew Whiting
March 2010