First Exploration of MWA Deep Field Point Source Population C. Williams - PhD Thesis J. Hewitt – reporting some analysis
Feb 22, 2016
First Exploration of MWA Deep Field Point Source Population
C. Williams - PhD ThesisJ. Hewitt – reporting some analysis
Motivation #1: verification of performance of array
• Compare to existing catalogs – source by source
• Compare to existing catalogs – statistics
• Compare multiply observed sources
• Source injection (uv data)
Spectral index distribution for low-frequency-selected and high-frequency-selected sources(De Breuck et al. 2000)
“Ultra-Steep-Spectrum” is alpha < -1.3 (between frequencies of 1420 and ~300 MHz)
Motivation #2: deeper southern sample of Ultra-Steep Spectrum Sources
Motivation #2: new sample of Ultra-Steep Spectrum Sources
De Breuck et al. 2004
Motivation #3: know your enemy – we want to subtract this foreground
Comparison Catalogs
• Molonglo Reference Catalog (MRC): 408 MHz, southern sky excluding Galactic plan, complete above 1 Jy, goes to 700 mJy, about 3 arc min resolution
• Culgoora Catalog: 80 and 160 MHz, not really a catalog, rather flux measurements of known sources
• Parkes-MIT-NRAO 5 GHz survey
• Source counts from Cambridge 150 MHz surveys
Galactic plane
Comparison of individual sources
Comparison of individual sources: Molonglo-MWA
Comparison of individual sources: Molonglo-MWA
Histogram of differences in source positions
Note declination shift
Comparison of individual sources: Molonglo-MWA
Histogram of differences in source positions, normalized
Comparison of individual sources: Molonglo-MWA
Differences in source positionsPlotted vs. distance from phase center
Comparison of individual sources: Molonglo-MWA
Differences in source positions, normalizedPlotted vs. distance from phase center
Comparison of individual sources: Molonglo-MWA
Working on comparison of flux densities (Chris Williams and Fakhri Zahedy, work in progress)
Comparison of statistics: Cambridge-MWA source counts
MWA sampleFlux density vs. distance from phase center
Comparison of statistics: Cambridge-MWA source counts
MWA sampleChoose “complete” region
Comparison of statistics: Cambridge-MWA source counts
MWA sample (very preliminary)Fits give power law index of -1.75 and -2.12Cambridge -1.8 (Gower 1966); -1.51 (de Mateo et al. 2002)
Comparison of statistics: Distribution of PMN-MWA spectral indices
MWA Ultra-SteepSpectrumSources
128-tile array will be MUCH more capable than this 32-tile array!
5 GHz – 150 MHz spectral indicesDeeper sample of Ultra-Steep Spectrum Sources
Comparison to other catalogs for verification
• Positions look good buto Shift o Increased error with distance from phase center
• Source counts in the right ballpark buto Correction for varying sensitivity across field neededo Careful fitting needed
• Spectral index distribution looks very plausible
Science
• New sample of Ultra Steep Spectrum sources• Learning about the EoR enemy
SUMMARY