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|Title:||Correcting the extended-source calibration for the Herschel-SPIRE Fourier-transform spectrometer||Authors:||Valtchanov, I.
Griffin, M. J.
Meyer, R. A.
Naylor, D. A.
Polehampton, E. T.
Spencer, L. D.
van der Wiel, M. H. D.
|Issue Date:||2018||Journal:||MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY||Number:||475||Issue:||1||First Page:||321||Abstract:||We describe an update to the Herschel-Spectral and Photometric Imaging Receiver (SPIRE) Fourier-transform spectrometer (FTS) calibration for extended sources, which incorporates a correction for the frequency-dependent far-field feedhorn efficiency, η<SUB>ff</SUB>. This significant correction affects all FTS extended-source calibrated spectra in sparse or mapping mode, regardless of the spectral resolution. Line fluxes and continuum levels are underestimated by factors of 1.3-2 in thespectrometer long wavelength band (447-1018 GHz; 671-294 μm) and 1.4-1.5 in the spectrometer short wavelength band (944-1568 GHz; 318-191 μm). The correction was implemented in the FTS pipeline version 14.1 and has also been described in the SPIRE Handbook since 2017 February. Studies based on extended-source calibrated spectra produced prior to this pipeline version should be critically reconsidered using the current products available in the Herschel Science Archive. Once the extended-source calibrated spectra are corrected for η<SUB>ff</SUB>, the synthetic photometry and the broad-band intensities from SPIRE photometer maps agree within 2-4 per cent - similar levels to the comparison of point-source calibrated spectra and photometry from point-source calibrated maps. The two calibration schemes for the FTS are now self-consistent: the conversion between the corrected extended-source and point-source calibrated spectra can be achieved with the beam solid angle and a gain correction that accounts for the diffraction loss.||URI:||http://hdl.handle.net/20.500.12386/28757||URL:||https://academic.oup.com/mnras/article/475/1/321/4718470||ISSN:||0035-8711||DOI:||10.1093/mnras/stx3178||Bibcode ADS:||2018MNRAS.475..321V||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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checked on Aug 4, 2021
checked on Aug 4, 2021
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