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Title: A FLUX SCALE FOR SOUTHERN HEMISPHERE 21 cm EPOCH OF REIONIZATION EXPERIMENTS

We present a catalog of spectral measurements covering a 100-200 MHz band for 32 sources, derived from observations with a 64 antenna deployment of the Donald C. Backer Precision Array for Probing the Epoch of Reionization (PAPER) in South Africa. For transit telescopes such as PAPER, calibration of the primary beam is a difficult endeavor and errors in this calibration are a major source of error in the determination of source spectra. In order to decrease our reliance on an accurate beam calibration, we focus on calibrating sources in a narrow declination range from –46° to –40°. Since sources at similar declinations follow nearly identical paths through the primary beam, this restriction greatly reduces errors associated with beam calibration, yielding a dramatic improvement in the accuracy of derived source spectra. Extrapolating from higher frequency catalogs, we derive the flux scale using a Monte Carlo fit across multiple sources that includes uncertainty from both catalog and measurement errors. Fitting spectral models to catalog data and these new PAPER measurements, we derive new flux models for Pictor A and 31 other sources at nearby declinations; 90% are found to confirm and refine a power-law model for flux density. Of particular importance ismore » the new Pictor A flux model, which is accurate to 1.4% and shows that between 100 MHz and 2 GHz, in contrast with previous models, the spectrum of Pictor A is consistent with a single power law given by a flux at 150 MHz of 382 ± 5.4 Jy and a spectral index of –0.76 ± 0.01. This accuracy represents an order of magnitude improvement over previous measurements in this band and is limited by the uncertainty in the catalog measurements used to estimate the absolute flux scale. The simplicity and improved accuracy of Pictor A's spectrum make it an excellent calibrator in a band important for experiments seeking to measure 21 cm emission from the epoch of reionization.« less
Authors:
;  [1] ; ; ;  [2] ; ;  [3] ;  [4] ;  [5] ; ; ;  [6] ; ;  [7] ; ;  [8] ;  [9]
  1. School of Earth and Space Exploration, Arizona State University, Tempe, AZ (United States)
  2. Astronomy Department, University of California, Berkeley, CA (United States)
  3. Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA (United States)
  4. Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, VA (United States)
  5. National Radio Astronomy Observatory, Socorro, NM (United States)
  6. Radio Astronomy Lab., University of California, Berkeley, CA (United States)
  7. National Radio Astronomy Observatory, Charlottesville, VA (United States)
  8. Square Kilometer Array, South Africa Project, Cape Town (South Africa)
  9. Cavendish Laboratory, Cambridge (United Kingdom)
Publication Date:
OSTI Identifier:
22270792
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 776; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCURACY; ANTENNAS; ASTROPHYSICS; CALIBRATION; CATALOGS; COSMIC RADIO SOURCES; FLUX DENSITY; GHZ RANGE; INDEXES; MHZ RANGE; MONTE CARLO METHOD; RADIOASTRONOMY; SOUTHERN HEMISPHERE; STARS; TELESCOPES