Flux calibration of the Herschel-SPIRE photometer

Abstract

We describe the procedure used to flux calibrate the three-band submillimetre photometer in the Spectral and Photometric Imaging REceiver (SPIRE) instrument on the Herschel Space Observatory. This includes the equations describing the calibration scheme, a justification for using Neptune as the primary calibration source, a description of the observations and data processing procedures used to derive flux calibration parameters (for converting from voltage to flux density) for every bolometer in each array, an analysis of the error budget in the flux calibration for the individual bolometers, and tests of the flux calibration on observations of primary and secondary calibrators. The procedure for deriving the flux calibration parameters is divided into two parts. In the first part, we use observations of astronomical sources in conjunction with the operation of the photometer internal calibration source to derive the unscaled derivatives of the flux calibration curves. To scale the calibration curves in Jy beam −1 V −1 , we then use observations of Neptune in which the beam of each bolometer is mapped using Neptune observed in a very fine scan pattern. The total instrumental uncertainties in the flux calibration for most individual bolometers is ∼ 0.5%, although a few bolometers have uncertainties of ∼ 1 − 5% because of issues with the Neptune observations. Based on application of the flux calibration parameters to Neptune observations performed using typical scan map observing modes, we determined that measurements from each array as a whole have instrumental uncertainties of 1.5%. This is considerably less than the absolute calibration uncertainty associated with the model of Neptune, which is estimated at 4%.

Star formation inz> 1 3CR host galaxies as seen byHerschel

“…The SPIRE 500 μm photometry should be considered tentative because the beam at this particular wavelength is large, and undetected sources in the region surrounding the AGN may contribute to the measured flux density. The SPIRE photometric uncertainties provided in Table 2 do not include the 4% uncertainty on the absolute flux calibration (Bendo et al 2013). Postage stamps of the resulting SPIRE maps, centred on the radio position of the objects, are included in Appendix E.…”

High-resolution, 3D radiative transfer modeling

“…We apply Gaussian kernels with FWHM of 3 (H) and 3.5 (J, K) to convolve the 2MASS data to the PACS 160 µm resolution (Aniano et al 2011). (d) Calibration uncertainties for the Herschel SPIRE instrument are assumed to be around 4% in each band, adding in quadrature the 4% absolute calibration error from the assumed models used for Neptune (SPIRE Observers' manual), and a random uncertainty of 1.5% accounting for the repetitive measurements of Neptune (see Bendo et al 2013).…”

TheHerschelVirgo Cluster Survey

“…Each source is then fitted with a Gaussian function using sourceExtractorTimeline, a timeline-based point source fitter (see Bendo et al 2013) implemented in HIPE 9.0.0 (Ott 2010). The method fits timeline data from all bolometers within an individual array with a two-dimensional Gaussian function.…”

“…First of all, the SPIRE data are flux calibrated at the timeline level using timeline-based PSF-fitting techniques (Bendo et al 2013), so the methods that we have used are consistent with the flux calibration measurements themselves and are therefore expected to be more accurate. Second, when the maps are produced from the timeline data, multiple measurements from the timelines are averaged together to produce the surface brightness measured in each pixel.…”