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PAPER’s Sweet Sixteen: Imaging the Low Frequency Sky with a Sixteen Element Array

PAPER’s Sweet Sixteen: Imaging the Low Frequency Sky with a Sixteen Element Array. Nicole Gugliucci for the PAPER Team* USNC/URSI National Radio Science Meeting 2009.

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PAPER’s Sweet Sixteen: Imaging the Low Frequency Sky with a Sixteen Element Array

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  1. PAPER’s Sweet Sixteen: Imaging the Low Frequency Sky with a Sixteen Element Array Nicole Gugliucci for the PAPER Team* USNC/URSI National Radio Science Meeting 2009 *Richard Bradley, Don Backer, Aaron Parsons, James Aguirre, AbhirupDatta, Chris Carilli, Griffin Foster, ChaitaliParashare, Erin Mastrantonio, Jason Manley

  2. Outline • PAPER science objectives • Overview of PAPER-16 • Calibration and Imaging • Early results! • Near and long-term plans

  3. Epoch of Reionization Signal vs. Foregrounds at 140 MHz MW synchrotron (Power) Point Sources MW free-free E-gal free-free EoR CMB (Multipole Moment) Assuming accurate removal of bright foreground sources!

  4. Epoch of Reionization Projected sensitivity of full array in Western Australia, compared to subtracted foregrounds 21-cm Power Spectrum Cosmic Variance of Power Spec PWA-128 Uniform PWA-128 Gaussian Synchrotron/1000 Point Sources/1000

  5. PAPER-16 in Green Bank, WV • Green Bank engineering array as part of the staged approach • Array design for ease of surveying while minimizing sidelobes of synthesized beam

  6. PAPER-16 Correlator • Flexible, FPGA-based packetized correlator • Wide-band, scalable

  7. PAPER-16 Goals • Testing of array components and for stability • Early imaging to improve on PWA-4 and PGB-8 results • Explore ionospheric effects • Begin all-sky survey 120-180 MHz with fluxes and spectral indices • Explore full-stokes imaging

  8. Calibration and Imaging • AIPY (Astronomical Imaging in Python) • Basic calibration (correlator effects, RFI removal) • Fit and model antenna positions, delays, passbands, crosstalk removal • Wide field-of-view imaging with HEALPix functionality (http://healpix.jpl.nasa.gov)

  9. Cyclic Calibration Simple pipeline using prior knowledge of array and sources, and is a cyclic process A. Parsons

  10. Into the data… Amplitude • RFI environment Time Frequency

  11. Into the data… Phase Amplitude • RFI environment • Rotating phases Time Frequency Frequency

  12. Into the data… Phase Amplitude • RFI environment • Rotating phases • Fit primary beam Time Frequency

  13. All-Sky Map • Example map combining GB and WA data • 138.8 – 174 MHz, log(Jy) scale, noise to .15 Jy/beam

  14. Measuring Fluxes… Ionosphere? Kassim et al. (2007) defines the isoplanatic patch as more specifically as the region of with a phase difference less than one radian at a particular observing frequency Isoplanatic Patch Amplitude vs. Time Work at the VLA at 74 MHz probed different ionospheric disturbances From Kitchin, Astrophysical Techniques Instantaneous amplitude or apparent defocusing (weak scintillation) of Vir A over 8 hours. Sunrise occurred at +3hr.

  15. Ionospheric Effects Kassim et al. (2007) defines the isoplanatic patch as more specifically as the region of with a phase difference less than one radian at a particular observing frequency Isoplanatic Patch Position vs. Time for RA and Dec Work at the VLA at 74 MHz probed different ionospheric disturbances From Kitchin, Astrophysical Techniques Refraction (or apparent position wander in both right ascension and declination) of Virgo A over the same timescale as before, 8 hours.

  16. Ionospheric Effects • Position wander over one hour Time (samples) Time (samples)

  17. Ionospheric Effects Cas A • Position wander over 24 hours Vir A

  18. Summary and Future Work • Calibration scheme in progress, includes fitting the primary beam and leads to generating all-sky maps and source fitting to visibilities • Ionosphere becomes a new challenge with source wander and scintillation • Future work will lead to survey with fluxes and spectral indices • Start taking dual-polarization data • PGB stability and ionosphere studies • PWA deployment in 2009!

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