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Comparison of absolute gain photometric calibration between planck/HFI and herschel/SPIRE at 545 and 857GHz

Bertincourt, B., Lagache, G., Martin, P. G., Schulz, B., Conversi, L., Dassas, K., Maurin, L., Abergel, A., Beelen, A., Bernard, J-P., Crill, B. P., Dole, H., Eales, Stephen Anthony ORCID: https://orcid.org/0000-0002-7394-426X, Gudmundsson, J. E., Lellouch, E., Moreno, R. and Perdereau, O. 2016. Comparison of absolute gain photometric calibration between planck/HFI and herschel/SPIRE at 545 and 857GHz. Astronomy and Astrophysics 588 , A107. 10.1051/0004-6361/201527313

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Abstract

We compare the absolute gain photometric calibration of the Planck/HFI and Herschel/SPIRE instruments on diffuse emission. The absolute calibration of HFI and SPIRE each relies on planet flux measurements and comparison with theoretical far-infrared emission models of planetary atmospheres. We measure the photometric cross calibration between the instruments at two overlapping bands, 545 GHz/500 μm and 857 GHz/350 μm. The SPIRE maps used have been processed in the Herschel Interactive Processing Environment (Version 12) and the HFI data are from the 2015 Public Data Release 2. For our study we used 15 large fields observed with SPIRE, which cover a total of about 120 deg2. We have selected these fields carefully to provide high signal-to-noise ratio, avoid residual systematics in the SPIRE maps, and span a wide range of surface brightness. The HFI maps are bandpass-corrected to match the emission observed by the SPIRE bandpasses. The SPIRE maps are convolved to match the HFI beam and put on a common pixel grid. We measure the cross-calibration relative gain between the instruments using two methods in each field, pixel-to-pixel correlation and angular power spectrum measurements. The SPIRE/HFI relative gains are 1.047 (±0.0069) and 1.003 (±0.0080) at 545 and 857 GHz, respectively, indicating very good agreement between the instruments. These relative gains deviate from unity by much less than the uncertainty of the absolute extended emission calibration, which is about 6.4% and 9.5% for HFI and SPIRE, respectively, but the deviations are comparable to the values 1.4% and 5.5% for HFI and SPIRE if the uncertainty from models of the common calibrator can be discounted. Of the 5.5% uncertainty for SPIRE, 4% arises from the uncertainty of the effective beam solid angle, which impacts the adopted SPIRE point source to extended source unit conversion factor, highlighting that as a focus for refinement.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Uncontrolled Keywords: methods: data analysis
Publisher: EDP Sciences
ISSN: 0004-6361
Date of First Compliant Deposit: 25 April 2017
Date of Acceptance: 21 January 2016
Last Modified: 21 May 2023 00:58
URI: https://orca.cardiff.ac.uk/id/eprint/100101

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