Presentation on theme: "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."— Presentation transcript:
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, Abhirup Datta, Chris Carilli, Griffin Foster, Chaitali Parashare, Erin Mastrantonio, Jason Manley
Outline PAPER science objectives Overview of PAPER-16 Calibration and Imaging Early results! Near and long-term plans
Epoch of Reionization Signal vs. Foregrounds at 140 MHz EoR E-gal free-free MW free-free Point Sources CMB MW synchrotron (Multipole Moment) (Power) Assuming accurate removal of bright foreground sources!
Epoch of Reionization Projected sensitivity of full array in Western Australia, compared to subtracted foregrounds PWA-128 Uniform Synchrotron/1000 Cosmic Variance of Power Spec PWA-128 Gaussian 21-cm Power Spectrum Point Sources/1000
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
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
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)
Cyclic Calibration Simple pipeline using prior knowledge of array and sources, and is a cyclic process A. Parsons
Into the data… RFI environment Time Frequency Amplitude
Into the data… RFI environment Rotating phases Time Frequency Amplitude Phase Frequency
Into the data… RFI environment Rotating phases Fit primary beam Time Frequency Amplitude Phase
All-Sky Map Example map combining GB and WA data 138.8 – 174 MHz, log(Jy) scale, noise to.15 Jy/beam
Measuring Fluxes… Ionosphere? From Kitchin, Astrophysical Techniques Isoplanatic Patch 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 Work at the VLA at 74 MHz probed different ionospheric disturbances Instantaneous amplitude or apparent defocusing (weak scintillation) of Vir A over 8 hours. Sunrise occurred at +3hr. Amplitude vs. Time
Ionospheric Effects From Kitchin, Astrophysical Techniques Isoplanatic Patch 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 Work at the VLA at 74 MHz probed different ionospheric disturbances Position vs. Time for RA and Dec Refraction (or apparent position wander in both right ascension and declination) of Virgo A over the same timescale as before, 8 hours.
Ionospheric Effects Position wander over one hour Time (samples)
Ionospheric Effects Position wander over 24 hours Cas A Vir A
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!