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
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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.
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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
EoRE-gal free-free
MW free-free
Point Sources
CMB
MW synchrotron
(Multipole Moment)
(Pow
er)
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 Correlator
• Flexible, FPGA-based packetized correlator
• Wide-band, scalable
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
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
Tim
e
Frequency
Amplitude
Into the data…
• RFI environment• Rotating phases
Tim
e
Frequency
Amplitude Phase
Frequency
Into the data…
• RFI environment• Rotating phases• Fit primary beam
Tim
e
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?Fr
om K
itchi
n, A
stro
phys
ical
Tec
hniq
ues
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 EffectsFr
om K
itchi
n, A
stro
phys
ical
Tec
hniq
ues
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)
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!