robbie auld1 simulated hi observations 4 th skads workshop, lisbon, 2-3 october 2008 simulated hi...
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Robbie Auld 1Simulated HI Observations4th SKADS Workshop, Lisbon, 2-3 October 2008
Simulated HI observationsSimulated HI observations
Robbie AuldCardiff University
collaborating with Oxford SKADS team
Robbie Auld 2Simulated HI Observations4th SKADS Workshop, Lisbon, 2-3 October 2008
OutlineOutline
• Description of the data pipeline
• Sky simulation (SEX)
• Telescope Simulation
• Detection Technique
• Comparisons: HIPASS vs. SEX
• dN/dz – SEX vs. SAX
• Future THINGS: IC 2574
Robbie Auld 3Simulated HI Observations4th SKADS Workshop, Lisbon, 2-3 October 2008
Data PipelineData Pipeline
Cleaned datacube
Web query
Sky model
SKA simulatorParselTongue script (HRK) that uses AIPS routines. Includes: antenna Tsys, antenna layout, gain factors, integration time per visibility, total observation time
Corrupted cube
Source Finder
S3 simulation (RW & FL) Query generated via the web interface, source list and datacube generated locally with S3 Tools.
Duchamp source finder package (ATNF)
Robbie Auld 4Simulated HI Observations4th SKADS Workshop, Lisbon, 2-3 October 2008
Resulting datacubeResulting datacube
Filled UV plane!
Robbie Auld 5Simulated HI Observations4th SKADS Workshop, Lisbon, 2-3 October 2008
Source detector: DuchampSource detector: DuchampLocates sets of contiguous voxels (3D pixels) above some threshold.
Threshold determination:
Manual (absolute value / S/N value)
Automatic (False Discovery Rate method)
Enhancement
Spectral smoothing (Hanning)
Spatial smoothing (Gaussian convolution)
A trous (wavelet procedure)
Voxels above threshold are flagged, merging algorithm rejects multiple detections
Robbie Auld 6Simulated HI Observations4th SKADS Workshop, Lisbon, 2-3 October 2008
Duchamp outputDuchamp output
Postscript file of all detections
VO compatible catalogue file
Robbie Auld 7Simulated HI Observations4th SKADS Workshop, Lisbon, 2-3 October 2008
Comparisons with HIPASSComparisons with HIPASS
Robbie Auld 8Simulated HI Observations4th SKADS Workshop, Lisbon, 2-3 October 2008
SEX shortcomingsSEX shortcomings
• HIMF (0 < z < 0.1)
Wilman et al. 2008
Robbie Auld 9Simulated HI Observations4th SKADS Workshop, Lisbon, 2-3 October 2008
SEX vs. SAX: dn/dz SEX vs. SAX: dn/dz
Abdalla & Rawlings (2005)
Diamonds – SAXStars – SEXSEX differential number counts too low.
Robbie Auld 10Simulated HI Observations4th SKADS Workshop, Lisbon, 2-3 October 2008
Future THINGS: IC 2574Future THINGS: IC 2574Integrated intensity Velocity Field
Explore effects of different array configurations with the galaxy in the local neighbourhood and then try moving it further away.