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 outputPostscript 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.