ASKAP Simulations

Background

The ASKAP Computing team is providing a series of simulated ASKAP observations for use by the Science Survey Teams. These simulations provide an opportunity for science teams to become acquainted with the scale of ASKAP data, to examine the quality of the ASKAP processing pipeline, and to test post-imaging analysis techniques such as source finding and stacking. If you are a member of a Survey Science Team and would like to be involved in the simulations, talk to your PI about joining ASKAP Working Group 1.

The data resulting from these simulations is provided on the ATNF computer system, and access is only possible for those with an ATNF account. We are aware that there are science team members that do not have an ATNF account, and so have created this page to provide simple access to certain files.

Note that the web server cannot provide files >2GB, so the larger files have been placed on the CASS FTP server. You can click the links to individual files, or connect with your ftp client to ftp.atnf.csiro.au, then go to pub/people/whi550/ASKAPsimulations and browse from there.

Quick Links

2010:

• Set #1: Continuum | Spectral-line
• Set #2: Continuum | Spectral-line
• Set #3: Continuum | Transients | Polarisation
• Set #4: Galactic HI
• Set #5: Spectral-line | Transients
• Set #6: Absorption-line | Continuum

2011:

• Set #7: Extragalactic | Galactic

Set #1, March 2010

The initial set of simulations released in March 2010 contain two sets of images: a continuum image to 10 uJy/beam over the full field-of-view, and a spectral-line (HI emission) cube over 1024 18.5kHz channels and the full field-of-view. Full descriptions can be found on the ASKAP Science and User Policy redmine site for the continuum and spectral-line cases (note that you need a redmine log-in for this - if you don't have one, ask your PI to get it set up).

Continuum

• Redmine page
• README file for the continuum simulations
• Restored image, in FITS format [4096x4096 pix, 65MB]
• Visibilities, in the form of CASA measurement sets [15GB]
• Model sky image, used as input into the simulations, in FITS format [5120x5120 pix, 101MB]
• Model sky image, on the same pixel scale as the restored image, smoothed to 30 arcsec, in FITS format [4096x4096 pix, 65MB]
• Lists of sources in the matching model image, in various formats:
  • Output from Duchamp, run on the matching model image to a threshold of 100uJy [60000+ sources, 16MB]
  • A kvis annotation file, as produced by Duchamp, corresponding to this source list [65MB]
  • An alternative annotation file, with just circles of size 30arcsec marking source positions (rather than detected pixels) [4.1MB]
• Source list from the matching model image, searched to 100uJy [60000+ sources, 16MB]
• Input catalogue, taken from the SKADS S3-SEX catalogue with a 1uJy flux limit.[~7.7M sources, 1004MB].

Spectral-line

• Redmine page
• README file for the spectral-line simulations
• Dirty cube, in CASA format (tar/gzip) [2560x2560x1024, 24GB, inflates to 26GB].
• Sub-cubes of the dirty cube, in FITS.gz format:
  • Full spatial field but only 41 channels [2560x2560x41, 963MB, inflates to 1.1GB]
  • Full spectral range but only 1.4deg field-of-view [512x512x1024, 951MB, inflates to 1.1GB]
• Model sky image, in CASA format (tar/gzip) [4096x4096x1024, 120MB, inflates to 65GB]
• Model sky image, on the same pixel scale as the restored image, smoothed to 30 arcsec,in CASA format (tar/gzip) [2560x2560x1024, 22GB, inflates to 26GB].
• Sub-cubes of the matching model, in FITS.gz format:
  • Full spatial field [2560x2560x41, 945MB, inflates to 1.1GB]
  • Full spectral range [512x512x1024, 862MB, inflates to 1.1GB]
• Source list from the matching model cube, searched to 100uJy [6000+ sources, 1.6MB]
• Input catalogue, taken from the SKADS S3-SAX catalogue.[10695 sources, 11MB]

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Set #2, April 2010

The second set of simulations build upon the first set. The primary change was to critically sample the synthetic beams, so that the noise is more uniform across the field of view. More information has been provided about the change in sensitivity across the field. Additionally, the spectral-line data has a couple of cubes with greatly reduced noise, providing data sets suitable for testing with source-finding software.

Continuum

• Redmine page
• Restored image (normalised to correct flux), in FITS format [4096x4096 pix, 65MB]
• Restored image (normalised to roughly constant noise), in FITS format [4096x4096 pix, 65MB]
• Noise-only image, in FITS format [4096x4096 pix, 65MB]
• Theoretical noise image, in FITS format [4096x4096 pix, 65MB]
• Weights image, in FITS format [4096x4096 pix, 65MB]
• PSF, in FITS format [4096x4096 pix, 65MB]
• Matching model image - the set of model components, put on the same pixel grid as the restored image and smoothed with the same beam, in FITS format [4096x4096 pix, 65MB]

Spectral-line

• Redmine page
• README file for the spectral-line simulations.
• Dirty cube, in CASA format (tar/gzip) [1536x1536x1024, 8.4 GB, inflates to 9.1 GB]
• Sub-cubes of the dirty cube, in FITS.gz format:
  • Full spatial field but only 41 channels [1536x1536x100, 1.7MB, inflates to 901MB]
  • Full spectral range but only 1.4deg field-of-view [512x512x1024, 2MB, inflates to 1.1GB]
• Cubes indicating the noise, in CASA format, tar/gzipped (Contact me if you want these.):
  • Theoretical noise, showing the sensitivity for the full cube. [1536x1536x1024, 5.1 GB, inflates to 9.1 GB]
  • Pure noise cube, derived from a blank field observation. [1536x1536x1024, 8.4 GB, inflates to 9.1 GB]
• Reduced-noise cubes, for use as source-finder tests. Each in fits.gz format. Two declinations are offered:
  • Dec = -45° [512x512x1024, 952 MB, inflates to 1.1 GB]
  • Dec = -3° [512x512x1024, 952 MB, inflates to 1.1 GB]
• PSF cubes, each 1536x1536x1024, in tgz CASA format, for declinations of -45° and -3° [each 8.4GB inflating to 9.1GB].
  • The first channel of these cubes are also available as FITS files for easy download: Dec = -45° or Dec = -3° [each 1536x1536, 9.1MB]
• Model sky image, on the same pixel scale as the restored image, smoothed to 30 arcsec,in CASA format (tar/gzip) [1536x1536x1024, 19MB, inflates to 9.1GB]
• Sub-cubes of the matching model, in FITS.gz format:
  • Full spatial field [1536x1536x100, 844MB, inflates to 901MB]
  • Full spectral range [512x512x1024, 949MB, inflates to 1.1GB]

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Set #3, May 2010

Continuum

This release of continuum data features high-resolution images resulting from using the full 36-antenna ASKAP array.

• Redmine page
• Input sky model, in FITS format [9215x9215 pix, 325MB]
• Restored image (normalised to correct flux), in FITS format [6144x6144 pix, 145MB]
• Restored image (normalised to roughly constant noise), in FITS format [6144x6144 pix, 145MB]
• Weights image, in FITS format [6144x6144 pix, 145MB]
• PSF, in FITS format [6144x6144 pix, 145MB]
• Residual image, in FITS format [6144x6144 pix, 145MB]
• Images of the full field and a close-up.
• Matching model image - the set of model components, put on the same pixel grid as the restored image and smoothed with the same beam, in FITS format [6144x6144 pix, 145MB]

Transients

This release contains continuum observations of a field with ten transient/variable sources.

• Redmine page
• Restored image, in FITS format [4096x4096 pix, 65MB]
• Weights image, in FITS format [4096x4096 pix, 65MB]
• PSF, in FITS format [4096x4096 pix, 65MB]
• Lightcurves, as a gzipped archive containing text files [28KB], or a CSV file, or a PDF plot.
• Images of the full field and a close-up.
• Various useful python scripts, to make the model images, do the simulation and plot the light curves.
• The log file from the imaging.

Polarisation

This release contains full-Stokes observations of a modified version of the SKADS S3-SEX catalogue, made over 32 8MHz channels.

• Redmine page
• README file.
• Catalogues: either the full set, in a gzipped tar archive of text file [1.9GB], or a smaller version in ASCII format [543MB], containing just those sources used, but with the correct positions (the full set are centred at RA,DEC=0,0). There is also an associated README file describing the catalogue content.
• Restored cube, in FITS format [1536x1536x4x32 pix, 1.2GB]
• Individual Stokes cubes: I | Q | U | V
• Weights cube, in FITS format [1536x1536x4x32 pix, 1.2GB]
• Residual cube, in FITS format [1536x1536x4x32 pix, 1.2GB]
• PSF cube, in FITS format [1536x1536x4x32 pix, 1.2GB]
• Model sky, in CASA format, tar/gzipped [4096x4096x4x32, 5.8GB, inflates to 8.1GB]
• Image of the polarised flux, in PNG format.

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Set #4, July 2010

Galactic HI

This release contains an observation of diffuse Galactic HI emission, using the GASS survey as an input.

• Redmine page
• README file for the Galactic simulations.
• Input model cube, [1501x1501x646, 5.5GB].
• Dirty images at resolutions of 30 arcsec [1400x1400x646 pix, 4.8GB], 60 arcsec [700x700x646 pix, 1.2GB], 90 arcsec [475x475x646 pix, 557MB] and 180 arcsec [250x250x646 pix, 155MB].
• Cleaned images at resolutions of 30 arcsec [1400x1400x646 pix, 4.8GB], 60 arcsec [700x700x646 pix, 1.2GB], 90 arcsec [475x475x646 pix, 557MB] and 180 arcsec [250x250x646 pix, 155MB].
• PSF images at resolutions of 30 arcsec [1400x1400x646 pix, 4.8GB], 60 arcsec [700x700x646 pix, 1.2GB], 90 arcsec [475x475x646 pix, 557MB] and 180 arcsec [250x250x646 pix, 155MB].
• Noise-only images at resolutions of 30 arcsec [1400x1400x646 pix, 4.8GB], 60 arcsec [700x700x646 pix, 1.2GB], 90 arcsec [475x475x646 pix, 557MB] and 180 arcsec [250x250x646 pix, 155MB].

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Set #5, October 2010

Spectral-line

This release contains observations of resolved HI galaxies (using observations of M31 and LMC as templates) at a variety of distances.

• Redmine page
• README file for the spectral-line simulations.
• Shell script for bulk downloading of all images.

We provide here links to individual files. Click on 'I' for the image cube, 'P' for the PSF cube and 'M' for the model input cube. Note that the spatial sizes for the image & PSF cubes are 600x600 pix for the 2km images, and 1800x1800 pix for the 6km.

Galaxy	Distance (Mpc)	# channels	2km			6km			Model
			clean	dirty	size	clean	dirty	size	cube	size
M31	5	160	I P	I P	220MB	I P	I P	1980MB	M	946x1078x160, 624MB
	10	160	I P	I P	220MB	I P	I P	1980MB	M	475x542x160, 158MB
	20	159	I P	I P	219MB	I P	I P	1968MB	M	477x544x159, 158MB
	50	157	I P	I P	216MB	I P	I P	1943MB	M	191x218x157, 26 MB
	100	153	I P	I P	211MB	I P	I P	1893MB	M	97x111x153, 6.6MB
	200	147	I P	I P	203MB	I P	I P	1819MB	M	50x57x147, 1.9MB
LMC	5	56	I P	I P	77MB	I P	I P	693MB	M	262x292x56, 17MB
	10	55	I P	I P	76MB	I P	I P	680MB	M	131x147x55, 4.1MB
	20	55	I P	I P	76MB	I P	I P	680MB	M	66x73x55, 1.1MB
	50	55	I P	I P	76MB	I P	I P	680MB	M	26x29x55, 192KB
	100	52	I P	I P	73MB	I P	I P	656MB	M	21x21x53, 121KB
	200	51	I P	I P	71MB	I P	I P	631MB	M	21x21x51, 119KB

Transients

This release contains observations of a radio continuum sky affected by refractive scintillation, with a number of Extreme Scattering Events included as well. The simulation had variability of sources sampled at 1-minute intervals, over an 8-hour synthesis observation. It also featured an example of sky-model subtraction, analogous to what will be used in ASKAP operations. Links to individual files are provided below:

• Redmine page
• README file for the transient simulations.
• Guide to the theory behind generating refractive scintillation lightcurves.
• Lightcurves used as input: either the full directory as a gzipped tar archive, or individual files:
  • All compact SKADS sources with S>0.1mJy
  • ESE lightcurves as provided by VAST: ese_0.5_4.0_31_32.txt | ese_2.0_1.0_31_32.txt | ese_4.0_4.0_31_32.txt
  • ESE lightcurves as used: ESE-0.5.txt | ESE-2.0.txt | ESE-4.0.txt
• The full continuum catalogue [ascii, 1004MB] plus the static model image and the sky model [both FITS.gz, 5120x5120 pix, 101MB].
• An image of the full field after 8hr integration, both dirty and cleaned, with associated psf and weights images. [Each FITS.gz, 2560x2560 pix, 26MB]
• An image of the full field after 8hr integration, but with a sky model removed prior to observation: dirty and clean. [Each FITS.gz, 2560x2560 pix, 26MB]

There are also a large number of additional files provided, being: the model sky, the visibilities, the dirty snapshot image and the dirty snapshot image with the model removed prior to observation. These are provided for each of the 480 timesteps. Rather than providing links here to the individual files, we provide a shell script that runs wget to access the files - this can be edited to only download part of the simulation if you wish. We provide links to the files for the first timestep for quick-look purposes:

• The model sky image [FITS.gz, 5120x5120 pix, 94MB, inflates to 101MB]
• The visibilities [tar-gzipped measurement set, 155MB, inflates to 186MB]
• The dirty image [FITS.gz, 2560x2560 pix, 24MB, inflates to 26MB]
• The dirty image with the sky model removed (prior to observation) [FITS.gz, 2560x2560 pix, 24MB, inflates to 26MB]

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Set #6, December 2010

Absorption-line

This ASKAP data release consists of simulated observations typical of the FLASH project. The simulation features both continuum and spectral-line data for a low-frequency observation, with the sky consisting of the SKADS continuum sky plus absorption-line components. This release was updated in April 2011 to correct errors in the original spectral-line simulation (the continuum simulation remains the same as released in December 2010).

• Redmine page
• README file for the absorption-line simulations.
• Catalogues:
  • Continuum source catalogue (>4 million sources, 534MB)
  • Continuum sources exhibiting absorption line components (209 entries, 32KB)
  • Absorption line component catalogue (600 components 52KB)
• Models:
  • Continuum model used as input into simulation (FITS, 50MB), and a version smoothed to same resolution and on same pixel scale as image (FITS, 35MB).
  • Spectral-line model used as input into simulation (tar-gzipped CASA image, 131MB inflating to 127GB!), and a version smoothed to same resolution and on same pixel scale as image (FITS, 35GB).
• Continuum images, all FITS, 3600x3600 pix, 50MB:
  • Restored image
  • PSF image
  • Clean model and residual images
  • Weights image
• Spectral-line cubes, all FITS, 3000x3000x1024 pix (unless otherwise stated).
  • Restored cube, plus a 50-channel subcube centred at z=0.79 (3000x3000x50, 1.7GB)
  • PSF cube, with two subcubes: one at z=0.79, and one of the central 600x600 pix over all channels (1.4GB)
  • Weights cube, plus the z=0.79 subcube.

Continuum

This ASKAP data release includes a simulation of a full continuum observation with critically sampled beams and 6 km baselines. The simulation builds upon the SST3 simulation by adding additional complex bright sources and large-scale diffuse sources (using models supplied by EMU WG1).

• Redmine page
• Input sky model, in FITS format [9215x9215 pix, 325MB]
• Matching model image - the set of model components, put on the same pixel grid as the restored image and smoothed with the same beam, in FITS format [6144x6144 pix, 145MB]
• Restored image (normalised to correct flux), in FITS format [6144x6144 pix, 145MB]
• Equalised restored image (normalised to roughly constant noise), in FITS format [6144x6144 pix, 145MB]
• Weights image, in FITS format [6144x6144 pix, 145MB]
• PSF, in FITS format [6144x6144 pix, 145MB]
• Residual image, in FITS format [6144x6144 pix, 145MB]
• Noise image, in FITS format [6144x6144 pix, 145MB]
• Difference image, being the smoothed model minus the residual, in FITS format [6144x6144 pix, 145MB]

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Set #7, September 2011

Combined Extragalactic simulation

This simulation will combine continuum, polarisation and spectral-line models, and replicate a large part of the processing planned to take place in the ASKAP pipeline. As the simulation work is underway at the moment, only the input sky models are available.

• Redmine page describing progress, with links to pages for each release.
• Sky models and catalogues:
  • Full-Stokes continuum model from POSSUM (a modified version of the SKADS S3-SEX catalogue, with polarisation and rotation measure information added), casa tar-gzipped format [8192x8192x300x4, 186GB compressed, inflates to 300GB]
  • Central 512x512 spatial pixels of the full-Stokes model, FITS format [512x512x300x4, 1.17GB]
  • First channel, full field of the full-Stokes model, FITS format [8192x8192x1x4, 1GB]
  • Input catalogue for the continuum model. This uses the same format as the earlier Polarisation simulation, although the content has changed. [tar-gzipped archive, 1.82 GB]
  • Smaller catalogue, containing only those sources within a 5x5 deg box, with the positions centred at (RA,DEC)=(12h30, -45d), as used for the model images (the positions in the full catalogue are centred at (RA,DEC)=(0,0)) [ascii file, 409MB]
  • Full-resolution spectral-line model, at same resolution as the full-Stokes continuum model, with 4096 channels. CASA image, tar-gzipped [8192x8192x4096, 1.1GB compressed, inflates to 1TB!]
  • Central 512x512 spatial pixels of the full-resolution spectral-line model, FITS format [512x512x4096, 4GB]
  • Continuum model matching the spectral-line model [8192x8192x1x1, 256MB]
• Images:
  • The following table provides links to the range of continuum images provided for the Extragalactic simulation. These are coded by 'I' for restored image, 'M' for the clean model, 'R' for residual, 'P' for PSF, 'S' for sensitivity and 'W' for weights. The multi-scale multi-frequency clean was used, with 2 terms, resulting in Taylor 0 and 1 terms for all images, plus Taylor 2 terms for the restored & model images. All MFS images are 5500x5500 pixels, and 116MB in size. All cubes are 5500x5500x300, and are FITS.gz format (inflating to 34GB).

    Stokes	MSMFS Taylor term			Cubes
    	0	1	2
    I	I M R P S W	I M R P S W	I M	I M R
    Q	I M R P S W	I M R P S W	I M	I M R
    U	I M R P S W	I M R P S W	I M	I M R
    V	I M R P S W	I M R P S W	I M	I M R

    [Note - the PSF, sensitivity and weights cubes are available, but they have been temporarily left off the FTP server for space considerations. Please contact me if you need them.]
  • For the extragalactic spectral-line simulation, there are two types of (dirty) images: a continuum-free simulation, and a continuum+line simulation with continuum subtraction, as well as images containing either no noise (ie. just the spectral-line model) or only noise (ie. no input model). We also provide PSF, sensitivity and weights images (these are the same for both simulations). Each cube is 2048x2048x4096 pixels, of size 65GB (CASA format, tarred):
    • Line-emission only image
    • FITS version of the line-emission only cube, trimmed spatially with subsection [401:1648,401:1648,*,*] [1248x1248x4096, 24GB]
    • Equalised version of the line-emission only cube (multiplied by the square-root of the normalised weights cube to normalise to roughly constant noise), plus the FITS version.
    • Continuum-subtracted image
    • Noise-only image
    • Noise-free image, plus a 24GB trimmed FITS version using the same subsection as above.
    • PSF cube is available, but temporarily not on the FTP server - contact me if you need it.
    • Sensitivity cube is available, but temporarily not on the FTP server - contact me if you need it.
    • Weights cube is available, but temporarily not on the FTP server - contact me if you need it.

Galactic HI + continuum + absorption

This simulation builds on the Galactic HI simulation from 2010, with the addition of a background continuum source model (taken from the SKADS S3-SEX catalogue) and HI absorption towards bright compact continuum sources. As the simulation work is underway at the moment, only the input sky models are available.

• Redmine page describing progress, with links to pages for each release.
• Sky models and catalogues:
  • Combined HI+continuum+absorption model, FITS format [1501x1501x646, 5.4GB]
  • Catalogue of absorption components that appear towards bright continuum point sources. First line explains what each column is. [ASCII CSV format, 56kB]
  • Continuum model only, FITS format [1501x1501, 8.7MB]
• Images: The following table provides links to individual images. Three different simulations are considered:
  • Simulation #1: a 9-beam field of view, with the Galactic plane between beams
  • Simulation #2: a 9-beam field of view, with the Galactic plane along the beam centres
  • Simulation #3: a compact 32-beam field of view
  The images are linked by the following codes: I=image; M=clean model; P=PSF, R=residual image (from cleaning); W=weights. Each cube has 646 channels, and an image size of: 1400x1400 (30" - 4.8GB), 700x700 (60" - 1.2GB), 475x475 (90" - 557MB) and 250x250 (180" - 155MB).

  Simulation #	Clean				Dirty
  	30"	60"	90"	180"	30"	60"	90"	180"
  1	I M R P W	I M R P W	I M R P W	I M R P W	I P W	I P W	I P W	I P W
  2	I M R P W	I M R P W	I M R P W	I M R P W	I P W	I P W	I P W	I P W
  3	I M R P W	I M R P W	I M R P W	I M R P W	I P W	I P W	I P W	I P W

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Matthew Whiting
Address:
Australia Telescope National Facility
CSIRO Astronomy & Space Science
PO Box 76, Epping,
NSW 1710,
Australia
Email:
Matthew.Whiting <at> csiro.au
ph: +61-2-9372-4683
Location:
You can find me in room 87A at Epping.

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