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The HERA-19 Commissioning Array: Direction-dependent Effects
- Source :
- Astrophysical Journal, vol 882, iss 1, The Astrophysical Journal, vol 882, iss 1
- Publication Year :
- 2018
- Publisher :
- Apollo - University of Cambridge Repository, 2018.
-
Abstract
- Foreground power dominates the measurements of interferometers that seek a statistical detection of highly-redshifted HI emission from the Epoch of Reionization (EoR). The chromaticity of the instrument creates a boundary in the Fourier transform of frequency (proportional to $k_\parallel$) between spectrally smooth emission, characteristic of the strong synchrotron foreground (the "wedge"), and the spectrally structured emission from HI in the EoR (the "EoR window"). Faraday rotation can inject spectral structure into otherwise smooth polarized foreground emission, which through instrument effects or miscalibration could possibly pollute the EoR window. Using data from the HERA 19-element commissioning array, we investigate the polarization response of this new instrument in the power spectrum domain. We perform a simple image-based calibration based on the unpolarized diffuse emission of the Global Sky Model, and show that it achieves qualitative redundancy between the nominally-redundant baselines of the array and reasonable amplitude accuracy. We construct power spectra of all fully polarized coherencies in all pseudo-Stokes parameters. We compare to simulations based on an unpolarized diffuse sky model and detailed electromagnetic simulations of the dish and feed, confirming that in Stokes I, the calibration does not add significant spectral structure beyond the expected level. Further, this calibration is stable over the 8 days of observations considered. Excess power is seen in the power spectra of the linear polarization Stokes parameters which is not easily attributable to leakage via the primary beam, and results from some combination of residual calibration errors and actual polarized emission. Stokes V is found to be highly discrepant from the expectation of zero power, strongly pointing to the need for more accurate polarized calibration.<br />Comment: 21 pages, 12 figures, submitted to ApJ
- Subjects :
- 010504 meteorology & atmospheric sciences
interferometers [instrumentation]
Atomic
Physical Chemistry
7. Clean energy
01 natural sciences
Spectral line
Particle and Plasma Physics
Astronomical interferometer
Stokes parameters
dark ages
instrumentation: interferometers
010303 astronomy & astrophysics
Physics
Linear polarization
Astrophysics::Instrumentation and Methods for Astrophysics
HERA
Polarization (waves)
observations [cosmology]
interferometric [techniques]
interferometer [instrumentation]
Amplitude
techniques: interferometric
symbols
reionization
dark ages, reionization, first star
Astrophysics - Instrumentation and Methods for Astrophysics
Astronomical and Space Sciences
observation [cosmology]
Physical Chemistry (incl. Structural)
first stars
FOS: Physical sciences
Astrophysics::Cosmology and Extragalactic Astrophysics
Astronomy & Astrophysics
symbols.namesake
Settore FIS/05 - Astronomia e Astrofisica
0103 physical sciences
Nuclear
dark ages, reionization, first stars
Reionization
Instrumentation and Methods for Astrophysics (astro-ph.IM)
Astrophysics::Galaxy Astrophysics
0105 earth and related environmental sciences
polarization
010308 nuclear & particles physics
Molecular
Astronomy and Astrophysics
Computational physics
Space and Planetary Science
13. Climate action
cosmology: observations
astro-ph.IM
Subjects
Details
- Database :
- OpenAIRE
- Journal :
- Astrophysical Journal, vol 882, iss 1, The Astrophysical Journal, vol 882, iss 1
- Accession number :
- edsair.doi.dedup.....7272901f39bc6522781a57bc2fc5795a
- Full Text :
- https://doi.org/10.17863/cam.26908