Faculty Research & Publicationshttps://hdl.handle.net/10133/35862024-03-29T06:28:20Z2024-03-29T06:28:20Z681Equity audit: University of LethbridgeBonifacio, GlendaDas, SauryaHodes, CarolineCheriuyot, Jacklynehttps://hdl.handle.net/10133/58602021-04-27T17:32:00Z2021-01-01T00:00:00Zdc.title: Equity audit: University of Lethbridge
dc.contributor.author: Bonifacio, Glenda; Das, Saurya; Hodes, Caroline; Cheriuyot, Jacklyne
2021-01-01T00:00:00ZRED project report: rights, equity, and diversity in postsecondary campus in Lethbridge 2019-2020Bonifacio, GlendaDas, SauryaHodes, CarolineCheruiyot, Jacklynehttps://hdl.handle.net/10133/58592021-04-28T06:05:21Z2021-01-01T00:00:00Zdc.title: RED project report: rights, equity, and diversity in postsecondary campus in Lethbridge 2019-2020
dc.contributor.author: Bonifacio, Glenda; Das, Saurya; Hodes, Caroline; Cheruiyot, Jacklyne
2021-01-01T00:00:00ZCalibration of Herschel SPIRE FTS observations at different spectral resolutionsMarchili, N.Hopwood, R.Fulton, T.Polehampton, E. T.Valtchanov, I.Zaretski, J.Naylor, David A.Griffin, M. J.Imhof, P.Lim, T.Lu, N.Makiwa, G.Pearson, C.Spencer, L.https://hdl.handle.net/10133/56342019-12-17T07:09:32Z2017-01-01T00:00:00Zdc.title: Calibration of Herschel SPIRE FTS observations at different spectral resolutions
dc.contributor.author: Marchili, N.; Hopwood, R.; Fulton, T.; Polehampton, E. T.; Valtchanov, I.; Zaretski, J.; Naylor, David A.; Griffin, M. J.; Imhof, P.; Lim, T.; Lu, N.; Makiwa, G.; Pearson, C.; Spencer, L.
dc.description.abstract: The SPIRE Fourier Transform Spectrometer on-board the Herschel Space Observatory had two standard spectral resolution modes for science observations: high resolution (HR) and low resolution (LR), which could also be performed in sequence (H+LR). A comparison of the HR and LR resolution spectra taken in this sequential mode revealed a systematic discrepancy in the continuum level. Analysing the data at different stages during standard pipeline processing demonstrates that the telescope and instrument emission affect HR and H+LR observations in a systematically different way. The origin of this difference is found to lie in the variation of both the telescope and instrument response functions, while it is triggered by fast variation of the instrument temperatures. As it is not possible to trace the evolution of the response functions using housekeeping data from the instrument subsystems, the calibration cannot be corrected analytically. Therefore, an empirical correction for LR spectra has been developed, which removes the systematic noise introduced by the variation of the response functions.
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2017-01-01T00:00:00ZCalibration of the Herschel SPIRE Fourier Transform SpectrometerSwinyard, B. M.Polehampton, E. T.Hopwood, R.Valtchanov, I.Lu, N.Fulton, T.Benielli, D.Imhof, P.Marchili, N.Baluteau, J.-P.Bendo, G. J.Ferlet, M.Griffin, M. J.Lim, T. L.Makiwa, G.Naylor, David A.Orton, G. S.Papageorgiou, A.Pearson, C. P.Schulz, B.Sidher, S. D.Spencer, L. D.van der Wiel, M. H. D.Wu, R.https://hdl.handle.net/10133/56332019-12-17T07:09:42Z2014-01-01T00:00:00Zdc.title: Calibration of the Herschel SPIRE Fourier Transform Spectrometer
dc.contributor.author: Swinyard, B. M.; Polehampton, E. T.; Hopwood, R.; Valtchanov, I.; Lu, N.; Fulton, T.; Benielli, D.; Imhof, P.; Marchili, N.; Baluteau, J.-P.; Bendo, G. J.; Ferlet, M.; Griffin, M. J.; Lim, T. L.; Makiwa, G.; Naylor, David A.; Orton, G. S.; Papageorgiou, A.; Pearson, C. P.; Schulz, B.; Sidher, S. D.; Spencer, L. D.; van der Wiel, M. H. D.; Wu, R.
dc.description.abstract: The Herschel Spectral and Photometric REceiver (SPIRE) instrument consists of an imaging photometric camera and an imaging Fourier Transform Spectrometer (FTS), both operating over a frequency range of∼450–1550GHz. In this paper, we briefly review the FTS design, operation, and data reduction, and describe in detail the approach taken to relative calibration (removal of instrument signatures) and absolute calibration against standard astronomical sources. The calibration scheme assumes a spatially extended source and uses the Herschel telescopeasprimarycalibrator.Conversionfromextendedtopoint-sourcecalibrationiscarried out using observations of the planet Uranus. The model of the telescope emission is shown to beaccuratetowithin6percent andrepeatable tobetterthan0.06percent and,bycomparison with models of Mars and Neptune, the Uranus model is shown to be accurate to within 3 per cent. Multiple observations of a number of point-like sources show that the repeatability of the calibration is better than 1 per cent, if the effects of the satellite absolute pointing error (APE) are corrected. The satellite APE leads to a decrement in the derived flux, which can be up to∼10 per cent (1 σ) at the high-frequency end of the SPIRE range in the first part of the mission, and∼4 per cent after Herschel operational day 1011. The lower frequency range of the SPIRE band is unaffected by this pointing error due to the larger beam size. Overall, for well-pointed, point-like sources, the absolute flux calibration is better than 6 per cent, and for extended sources where mapping is required it is better than 7 per cent.
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2014-01-01T00:00:00ZCorrecting the extended-source calibration for the Herschel SPIRE Fourier-transform spectrometerValtchanov, I.Hopwood, R.Bendo, G.Benson, Christopher S.Conversi, L.Fulton, T.Griffin, M. J.Joubaud, T.Lim, T.Lu, N.Marchili, N.Makiwa, G.Meyer, R. A.Naylor, David A.North, C.Papageorgiou, A.Pearson, C.Polehampton, E. T.Scott, J.Schulz, B.Spencer, L. D.van der Wiel, M. H. D.Wu, R.https://hdl.handle.net/10133/56312024-03-08T23:02:41Z2017-01-01T00:00:00Zdc.title: Correcting the extended-source calibration for the Herschel SPIRE Fourier-transform spectrometer
dc.contributor.author: Valtchanov, I.; Hopwood, R.; Bendo, G.; Benson, Christopher S.; Conversi, L.; Fulton, T.; Griffin, M. J.; Joubaud, T.; Lim, T.; Lu, N.; Marchili, N.; Makiwa, G.; Meyer, R. A.; Naylor, David A.; North, C.; Papageorgiou, A.; Pearson, C.; Polehampton, E. T.; Scott, J.; Schulz, B.; Spencer, L. D.; van der Wiel, M. H. D.; Wu, R.
dc.description.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, ηff. 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 the spectrometer 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 correctionwasimplementedintheFTSpipelineversion14.1andhasalsobeendescribedinthe 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 ηff, the synthetic photometry and the broad-band intensities from SPIRE photometer maps agree within 2–4percent – 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.
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2017-01-01T00:00:00ZFar-infrared/submillimetre properties of pre-stellar cores L1521E, L1521F and L1689B as revealed by the Herschel SPIRE instrument - I. Central positionsMakiwa, G.Naylor, David A.van der Wiel, M. H. D.Ward-Thompson, D.Kirk, J. M.Eyres, S.Abergel, A.Köhler, M.https://hdl.handle.net/10133/56302019-12-13T07:05:33Z2016-01-01T00:00:00Zdc.title: Far-infrared/submillimetre properties of pre-stellar cores L1521E, L1521F and L1689B as revealed by the Herschel SPIRE instrument - I. Central positions
dc.contributor.author: Makiwa, G.; Naylor, David A.; van der Wiel, M. H. D.; Ward-Thompson, D.; Kirk, J. M.; Eyres, S.; Abergel, A.; Köhler, M.
dc.description.abstract: Dust grains play a key role in the physics of star-forming regions, even though they constitute only ∼1 per cent of the mass of the interstellar medium. The derivation of accurate dust parameters such as temperature (Td), emissivity spectral index (β) and column density requires broad-band continuum observations at far-infrared wavelengths. We present Herschel-Spectral and Photometric Imaging Receiver Array (SPIRE) Fourier Transform Spectrometer (FTS) measurements of three starless cores: L1521E, L1521F and L1689B, covering wavelengths between 194 and 671 µm. This paper is the first to use our recently updated SPIRE-FTS intensity calibration, yielding a direct match with SPIRE photometer measurements of extended sources. In addition, we carefully assess the validity of calibration schemes depending on-source extent and on the strength of background emission. The broad-band far-infrared spectra for all three sources peak near 250 µm. Our observations therefore provide much tighter constraints on the spectral energy distribution (SED) shape than measurements that do not probe the SED peak. The spectra are fitted using modified blackbody functions, allowing both Td and β to vary as free parameters.This yields Td of9.8±0.2,15.6±0.5and10.9±0.2K and corresponding β of 2.6∓0.9, 0.8∓0.1 and 2.4∓0.8 for L1521E, L1521F and L1689B, respectively.Thederivedcoremassesare1.0±0.1,0.10±0.01and0.49±0.05M ,respectively. The core mass/Jeans mass ratios for L1521E and L1689B exceed unity indicating that they are unstable to gravitational collapse, and thus pre-stellar cores. By comparison, the elevated temperature and gravitational stability of L1521F support previous arguments that this source is more evolved and likely a protostar.
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2016-01-01T00:00:00ZSignatures of warm carbon monoxide in protoplanetary discs observed with Herschel SPIREvan der Wiel, M. H. D.Naylor, David A.Kamp, I.Ménard, F.Thi, W.-F.Woitke, P.Olofsson, G.Pontoppidan, K. M.Di Francesco, J.Glauser, A. M.Greaves, J. S.Ivison, R. J.https://hdl.handle.net/10133/56292019-12-13T07:05:43Z2014-01-01T00:00:00Zdc.title: Signatures of warm carbon monoxide in protoplanetary discs observed with Herschel SPIRE
dc.contributor.author: van der Wiel, M. H. D.; Naylor, David A.; Kamp, I.; Ménard, F.; Thi, W.-F.; Woitke, P.; Olofsson, G.; Pontoppidan, K. M.; Di Francesco, J.; Glauser, A. M.; Greaves, J. S.; Ivison, R. J.
dc.description.abstract: Molecular gas constitutes the dominant mass component of protoplanetary discs. To date, these sources have not been studied comprehensively at the longest far-infrared and shortest submillimetre wavelengths. This paper presents Herschel SPIRE FTS spectroscopic observations towards 18 protoplanetary discs, covering the entire 450–1540GHz (666–195 μm) range at ν/ ν ≈ 400–1300. The spectra reveal clear detections of the dust continuum and, in six targets, a significant amount of spectral line emission primarily attributable to 12CO rotational lines. Other targets exhibit little to no detectable spectral lines. Low signal-to-noise detections also include signatures from 13CO, [CI] and HCN. For completeness, we present upper limits of non-detected lines in all targets, including low-energy transitions of H2O and CH+ molecules. The 10 12CO lines that fall within the SPIRE FTS bands trace energy levels of ∼50–500K. Combined with lower and higher energy lines from the literature, we compare the CO rotational line energy distribution with detailed physical–chemical models, for sources where these are available and published. Our 13CO line detections in the disc around Herbig Be star HD 100546 exceed, by factors of ∼10–30, the values predicted by a model that matches a wealth of other observational constraints, including the SPIRE 12COladder. To explain the observed 12CO/13COratio, it may be necessary to consider the combined effects of optical depth and isotope selective (photo)chemical processes. Considering the full sample of 18 objects, we find that the strongest line emission is observed in discs around Herbig Ae/Be stars, although not all show line emission. In addition, two of the six T Tauri objects exhibit detectable 12CO lines in the SPIRE range.
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2014-01-01T00:00:00ZSystematic characterization of the Herschel SPIRE Fourier Transform SpectrometerHopwood, R.Polehampton, E. T.Valtchanov, I.Swinyard, B. M.Fulton, T.Lu, N.Marchili, N.van der Wiel, M. H. D.Benielli, D.Imhof, P.Baluteau, J.-P.Pearson, C.Clements, D. L.Griffin, M. J.Lim, T. L.Makiwa, G.Naylor, David A.Noble, G.Puga, E.Spencer, L. D.https://hdl.handle.net/10133/56282019-12-13T07:05:41Z2015-01-01T00:00:00Zdc.title: Systematic characterization of the Herschel SPIRE Fourier Transform Spectrometer
dc.contributor.author: Hopwood, R.; Polehampton, E. T.; Valtchanov, I.; Swinyard, B. M.; Fulton, T.; Lu, N.; Marchili, N.; van der Wiel, M. H. D.; Benielli, D.; Imhof, P.; Baluteau, J.-P.; Pearson, C.; Clements, D. L.; Griffin, M. J.; Lim, T. L.; Makiwa, G.; Naylor, David A.; Noble, G.; Puga, E.; Spencer, L. D.
dc.description.abstract: A systematic programme of calibration observations was carried out to monitor the performance of the Spectral and Photometric Imaging REceiver (SPIRE) Fourier Transform Spectrometer (FTS) instrument on board the Herschel Space Observatory. Observations of planets (including the prime point-source calibrator, Uranus), asteroids, line sources, dark sky and cross-calibration sources were made in order to monitor repeatability and sensitivity, and to improve FTS calibration. We present a complete analysis of the full set of calibration observations and use them to assess the performance of the FTS. Particular care is taken to understand and separate out the effect of pointing uncertainties, including the position of the internal beam steering mirror for sparse observations in the early part of the mission. The repeatability of spectral-line centre positions is <5kms−1, for lines with signal-to-noise ratios>40, corresponding to <0.5–2.0 percent of a resolution element. For spectral-lineflux,the repeatability is better than 6percent, which improves to 1–2percent for spectra corrected for pointing offsets. The continuum repeatability is 4.4percent for the SPIRE Long Wavelength spectrometer (SLW) band and 13.6percent for the SPIRE Short Wavelength spectrometer (SSW) band, which reduces to ∼1percent once the data have been corrected for pointing offsets. Observations of dark sky were used to assess the sensitivity and the systematic offset in the continuum, both of which were found to be consistent across the FTS-detector arrays. Theaveragepoint-sourcecalibratedsensitivityforthecentredetectorsis0.20and0.21Jy[1σ; 1h],forSLWandSSW.Theaveragecontinuumoffsetis0.40JyfortheSLWbandand0.28Jy for the SSW band.
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2015-01-01T00:00:00ZThe data processing pipeline for the Herschel SPIRE Fourier Transform SpectrometerFulton, T.Naylor, David A.Polehampton, E. T.Valtchanov, I.Hopwood, R.Lu, N.Baluteau, J.-P.Mainetti, G.Pearson, C.Papageorgiou, A.Guest, S.Zhang, L.Imhof, P.Swinyard, B. M.Griffin, M. J.Lim, T. L.https://hdl.handle.net/10133/56272019-12-13T07:05:35Z2016-01-01T00:00:00Zdc.title: The data processing pipeline for the Herschel SPIRE Fourier Transform Spectrometer
dc.contributor.author: Fulton, T.; Naylor, David A.; Polehampton, E. T.; Valtchanov, I.; Hopwood, R.; Lu, N.; Baluteau, J.-P.; Mainetti, G.; Pearson, C.; Papageorgiou, A.; Guest, S.; Zhang, L.; Imhof, P.; Swinyard, B. M.; Griffin, M. J.; Lim, T. L.
dc.description.abstract: We present the data processing pipeline to generate calibrated data products from the Spectral and Photometric Imaging Receiver (SPIRE) imaging Fourier Transform Spectrometer on the Herschel Space Observatory. The pipeline processes telemetry from SPIRE observations and produces calibrated spectra for all resolution modes. The spectrometer pipeline shares some elements with the SPIRE photometer pipeline, including the conversion of telemetry packets into data timelines and calculation of bolometer voltages. We present the following fundamental processing steps unique to the spectrometer: temporal and spatial interpolation of the scan mechanism and detector data to create interferograms; Fourier transformation; apodization; and creation of a data cube. We also describe the corrections for various instrumental effects including first- and second-level glitch identification and removal, correction of the effects due to emission from the Herschel telescope and from within the spectrometer instrument, interferogram baseline correction, temporal and spatial phase correction, non-linear response of the bolometers, and variation of instrument performance across the focal plane arrays. Astronomical calibration is based on combinations of observations of standard astronomical sources and regions of space known to contain minimal emission.
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2016-01-01T00:00:00ZTime crystals from minimum time uncertaintyFaizal, MirKhalil, Mohammed M.Das, Sauryahttps://hdl.handle.net/10133/56252019-12-12T07:05:17Z2016-01-01T00:00:00Zdc.title: Time crystals from minimum time uncertainty
dc.contributor.author: Faizal, Mir; Khalil, Mohammed M.; Das, Saurya
dc.description.abstract: Motivated by the Generalized Uncertainty Principle, covariance, and a minimum measurable time, we propose a deformation of the Heisenberg algebra and show that this leads to corrections to all quantum mechanical systems. We also demonstrate that such a deformation implies a discrete spectrum for time. In other words, time behaves like a crystal. As an application of our formalism, we analyze the effect of such a deformation on the rate of spontaneous emission in a hydrogen atom.
dc.description: Sherpa Romeo green journal. Open access article. Creative Commons Attribution 4.0 International License (CC BY 4.0) applies
2016-01-01T00:00:00Z