A Flux Scale for Southern Hemisphere 21cm EoR Experiments

Abstract

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 reliance on accurate beam calibration, we focus on calibrating sources in a narrow declination range from -46d to -40d. 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% of these confirm and refine a power-law model for flux density. Of note is the new Pictor A flux model, which is accurate to 1.4% and shows, in contrast to previous models, that between 100 MHz and 2 GHz, 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 for experiments seeking to measure 21cm emission from the Epoch of Reionization.

Accepted to ApJ, includes two data files

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Cited by in corpus (22)

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• PAPER-64 Constraints on Reionization: The 21cm Power Spectrum at z=8.4
• A simplified, lossless re-analysis of PAPER-64
• The Impact of Modeling Errors on Interferometer Calibration for 21 cm Power Spectra
• First Limits on the 21 cm Power Spectrum during the Epoch of X-ray heating
• MITEoR: A Scalable Interferometer for Precision 21 cm Cosmology
• Multi-redshift limits on the 21cm power spectrum from PAPER
• The Murchison Widefield Array 21 cm Power Spectrum Analysis Methodology
• Light cone effect on the reionization 21-cm signal II: Evolution, anisotropies and observational implications
• Modelling of the Spectral Energy Distribution of Fornax A: Leptonic and Hadronic Production of High Energy Emission from the Radio Lobes
• Mapmaking for Precision 21 cm Cosmology
• Absolute Calibration Strategies for the Hydrogen Epoch of Reionization Array and Their Impact on the 21 cm Power Spectrum
• Improved 21 cm Epoch Of Reionization Power Spectrum Measurements with a Hybrid Foreground Subtraction and Avoidance Technique
• Constraining Polarized Foregrounds for EoR Experiments I: 2D Power Spectra from the PAPER-32 Imaging Array
• Constraining Polarized Foregrounds for EOR Experiments II: Polarization Leakage Simulations in the Avoidance Scheme
• New Limits on Polarized Power Spectra at 126 and 164 MHz: Relevance to Epoch of Reionization Measurements
• Brute-Force Mapmaking with Compact Interferometers: A MITEoR Northern Sky Map from 128 MHz to 175 MHz
• The HERA-19 Commissioning Array: Direction Dependent Effects
• Measuring HERA's primary beam in-situ: methodology and first results
• Extracting the 21 cm EoR signal using MWA drift scan data
• The Correlation Calibration of PAPER-64 data
• It's Always Darkest Before the Cosmic Dawn: Early Results from Novel Tools and Telescopes for 21 cm Cosmology