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