Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy XI
The next generation of astronomical space-based far-infrared (FIR) missions require ultra-sensiti... more The next generation of astronomical space-based far-infrared (FIR) missions require ultra-sensitive spectroscopy as a diagnostic tool. These instruments use ultra-sensitive detector technologies to attain unprecedented levels of spectral observing sensitivity. The reception patterns of the individual detectors consist of individually coherent orthogonal field distributions, or equivalently, they are few-mode (5-20), to increase the spectral-spatial coupling to the astronomical source. However, the disadvantage of few-mode detectors is an increase in coupling to external (from the sky or warm telescope optics) and internal (from the instrument itself) straylight, which can greatly affect the measurement of the source spectrum. Therefore, understanding the spectral-spatial few-mode behaviour of these systems in detail, and developing verification and calibration strategies, are crucial to ensure that the science goals of these future mission are met. Since conventional modelling techniques are less suited to address this problem, we developed a modal framework to model, analyse, and address these issues. 1 In this paper, we use Herschel 's Spectral and Photometric Imaging REceiver (SPIRE) as a case study, because its optical design is representative for future FIR missions and illustrative to highlight calibration issues observed in-flight, while including straylight. Our analysis consist out of two part. In the first part, we use our modal framework to simulate the few-mode SPIRE Fourier Transform Spectrometer (FTS). In the second part, we carry out a end-to-end frequency-dependent partially coherent analysis of Herschel-SPIRE. These simulations offer a qualitative explanation for the few-mode behaviour observed in-flight. Furthermore, we use the Herschel-SPIRE case-study to demonstrate how the modelling framework can be used to support the design, verification and calibration of spectrometers for future FIR missions. The modal framework is not only limited to the spectrometers discussed, but it can be used to simulated a wide range of spectrometers, such as low-resolution gratings and high-spectral resolution Fabry-Pérot interferometers.
This proposal advocates for a collective science initiative within Canada to better understand th... more This proposal advocates for a collective science initiative within Canada to better understand the nature of interstellar dust through its entire life cycle. Interstellar dust grains (solid particles) are a fundamental probe of the Universe. Dust is present across multiple scales that probe the physical properties of (1) dense and diffuse clouds in the multi-phase ISM in galaxies, (2) the atmospheres of evolved stars, (3) the ejecta of stellar remnants, (4) circumstellar disks, and (5) the high-redshift universe. <br> <br> Even though dust is such a key component in how we perceive entire galaxies, characterize stellar evolution, and trace both star and planet formation, we don't have good physical and chemical constraints on the dust grains themselves. What are dust grains made out of? What is their size distribution? What is their structure? These questions are a key problem in using dust as a probe of the universe. These questions are also non-trivial, because dus...
Imaging applications at terahertz frequencies are, in general, limited to relatively low spatial ... more Imaging applications at terahertz frequencies are, in general, limited to relatively low spatial resolution due to the effects of diffraction. By using a subwavelength aperture in the near-field, however, it is possible to achieve subwavelength resolution, although low transmission through the aperture limits the sensitivity of this approach. Plasmonic lenses in the form of bullseye structures, which consist of a circular subwavelength aperture surrounded by concentric periodic corrugations, have demonstrated enhanced transmission, thereby increasing the utility of near-field imaging configurations. In this paper, the design, fabrication, and experimental performance of plasmonic lenses optimized for 300 GHz are discussed. While nanofabrication techniques are required for optical applications, microfabrication techniques are sufficient for terahertz applications. The process flow for fabricating a double-sided bullseye structure using a precision micromilling technique is described. Transmission and beam profile measurements using a customized terahertz testbed are presented.
Fourier Transform Spectroscopy/ Hyperspectral Imaging and Sounding of the Environment, 2005
We present the University of Lethbridge Transmission and Radiance Atmospheric Model (ULTRAM). A c... more We present the University of Lethbridge Transmission and Radiance Atmospheric Model (ULTRAM). A comparison with FASCODE is presented, along with several sample applications of ULTRAM. The source code is freely available and easily customized.
Proceedings of the International Astronomical Union, 2013
Herbig Ae/Be objects, like their lower mass counterparts T Tauri stars, are seen to form a stable... more Herbig Ae/Be objects, like their lower mass counterparts T Tauri stars, are seen to form a stable circumstellar disk which is initially gas-rich and could ultimately form a planetary system. We present Herschel SPIRE 460–1540 GHz spectra of five targets out of a sample of 13 young disk sources, showing line detections mainly due to warm CO gas.
We present the performance characteristics of a water vapour monitor that has been permanently de... more We present the performance characteristics of a water vapour monitor that has been permanently deployed at ESO's Paranal observatory as a part of the VISIR upgrade project. After a careful analysis of the requirements and an open call for tender, the Low Humidity and Temperature Profiling microwave radiometer (LHATPRO), manufactured by Radiometer Physics GmbH (RPG), has been selected. The unit measures several channels across the strong water vapour emission line at 183 GHz, necessary for resolving the low levels of precipitable water vapour (PWV) that are prevalent on Paranal (median ~2.5 mm). The unit comprises the above humidity profiler (183-191 GHz), a temperature profiler (51-58 GHz), and an infrared radiometer (~10 μm) for cloud detection. The instrument has been commissioned during a 2.5 week period in Oct/Nov 2011, by comparing its measurements of PWV and atmospheric profiles with the ones obtained by 22 radiosonde balloons. In parallel an IR radiometer (Univ. Lethbridge) has been operated, and various observations with ESO facility spectrographs have been taken. The RPG radiometer has been validated across the range 0.5-9 mm demonstrating an accuracy of better than 0.1 mm. The saturation limit of the radiometer is about 20 mm. Currently, the radiometer is being integrated into the Paranal infrastructure to serve as a high time-resolution monitor in support of VLT science operations. The water vapour radiometer's ability to provide high precision, high time resolution information on this important aspect of the atmosphere will be most useful for conducting IR observations with the VLT under optimal conditions.
This letter reports the discovery of excess emission at the position of the H I n=22-21 Rydberg t... more This letter reports the discovery of excess emission at the position of the H I n=22-21 Rydberg transition in submillimetre solar spectra taken at the extreme solar limb. This emission feature at 22.096+/-0.003 cm-1 shows significant limb brightening, reaching intensities of 11% above the adjacent spectral continuum with line shapes fitted best by Gaussian functions with widths of 0.018+/-0.004 cm-1. This measurement represents the highest-n Rydberg line of H I detected to date in the solar spectrum.
Submillimetre continuum radiation allows us to probe cold objects, particularly the earliest, dus... more Submillimetre continuum radiation allows us to probe cold objects, particularly the earliest, dusty phases of star formation, high-redshift galaxies and circumstellar disks. The submillimetre window gives a unique view of the physical and dynamical conditions in the neutral and molecular interstellar medium. In the next decade a combination of wide-field surveys with single-dish telescopes and targeted follow-up with ALMA and other facilities should enable rapid progress in answering questions about the origins of planetary systems, stars and galaxies.
Over the last 40 years enormous advances have been made in infrared astronomy. Virtually all of t... more Over the last 40 years enormous advances have been made in infrared astronomy. Virtually all of these can be traced to the use of space-based telescopes, which avoid the deleterious effects of the earth's atmosphere, and continued improvements in detector sensitivity and instrument design. Since its initial and modest contributions to previous infrared space astronomy missions, starting with ISO through to Herschel, Canada has grown in stature and is now recognized as a partner of choice by leading space agencies and scientific consortia embarking on the next generation of IR space astronomy missions. This white paper reviews the history of Canada's contributions to IR space astronomy missions and presents the case for Canadian participation in the ESA-JAXA SPICA mission, which has been selected as one of three finalists for ESA's fifth medium class mission, M5.<br> <br> Observations at far-infrared (FIR) wavelengths are optimal, not only for exploring galaxy...
Abstract. Submillimetre spectra taken near to the solar limb with a polarizing interferometer on ... more Abstract. Submillimetre spectra taken near to the solar limb with a polarizing interferometer on the James Clerk Maxwell Telescope have been compared with disk-centre spectra to reveal a limb-brightened feature whose peak intensity occurs at the predicted frequency of the n=20–19 Rydberg transition in H i at 29.622 cm −1. A shoulder on this peak, at 29.65 cm −1, has been tentatively assigned to the equivalent transition in Mg i. The H i line exhibits limb brightening of up to 9 % of the diskcentre continuum intensity. The intensity of the Mg i line is about half of the H i line intensity across the observed region near to the limb. Widths of the H i line are between 0.020 and 0.027 cm −1, smaller than predicted by current models of this line in the Sun’s spectrum. These measurements represent the highest-n Rydberg lines detected to date in the solar spectrum. The measured line intensity, line width, limb brightening and the relative heights of the contributions from H i and Mg i pla...
The Spectral and Photometric Imaging Receiver (SPIRE) is one of three scientific instruments onbo... more The Spectral and Photometric Imaging Receiver (SPIRE) is one of three scientific instruments onboard the European Space Agency's Herschel Space Observatory launched on 14 May 2009. The low to medium resolution spectroscopic capability of SPIRE is provided by an imaging Fourier transform spectrometer of the Mach-Zehnder configuration. Results from the in flight performance verification the instrument design specifications is reviewed.
OSA Optical Sensors and Sensing Congress 2021 (AIS, FTS, HISE, SENSORS, ES), 2021
This paper describes the development and status of a cryogenic, far-infrared, post- dispersed, po... more This paper describes the development and status of a cryogenic, far-infrared, post- dispersed, polarizing FTS (PDPFTS), a candidate instrument concept for the next generation of far- infrared astronomical space telescopes.
Monthly Notices of the Royal Astronomical Society, 2016
Dust grains play a key role in the physics of star-forming regions, even though they constitute o... more Dust grains play a key role in the physics of star-forming regions, even though they constitute only ∼1 % of the mass of the interstellar medium. The derivation of accurate dust parameters such as temperature (T d), emissivity spectral index (β) and column density requires broadband continuum observations at far-infrared wavelengths. We present Herschel-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 broadband 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 T d and β to vary as free parameters. This yields T d of 9.8±0.2 K, 15.6±0.5 K and 10.9±0.2 K and corresponding β of 2.6∓0.9, 0.8∓0.1 and 2.4∓0.8 for L1521E, L1521F and L1689B respectively. The derived core masses are 1.0±0.1, 0.10±0.01 and 0.49±0.05 M , respectively. The core mass/Jeans mass ratios for L1521E and L1689B exceed unity indicating that they are unstable to gravitational collapse, and thus prestellar cores. By comparison, the elevated temperature and gravitational stability of L1521F support previous arguments that this source is more evolved and likely a protostar.
The Blue Sky Transmission and Radiance Atmospheric Model (BTRAM) was developed in an effort to cr... more The Blue Sky Transmission and Radiance Atmospheric Model (BTRAM) was developed in an effort to create a radiative transfer model that was both fast and fully customisable by the user. A number of earlier radiative transfer models, such as FASCODE and MODTRAN, offer powerful simulation capabilities, but have interfaces that make it difficult to tailor the model to the specific needs of a user. BTRAM, developed in the Interactive Data Language (IDL®) [5], provides users with a straightforward interface that allows the efficient calculation of radiative transfer through custom atmospheric profiles or gas cells, from submillimetre to visible wavelengths, all at variable resolution. BTRAM also allows the user to convolve simulated spectra with custom instrumental line shapes, providing a more realistic simulation of instrumental performance. This paper discusses the radiative transfer calculations used in the BTRAM code and presents applications of BTRAM simulated spectra from the far-infrared/submillimetre through to the visible spectral region.
Space Telescopes and Instrumentation I: Optical, Infrared, and Millimeter, 2006
This thesis was typeset with BlgX using a modified version of the the University of Cali fornia P... more This thesis was typeset with BlgX using a modified version of the the University of Cali fornia PhD dissertation class file, ucthesis. els. Unless otherwise noted, all figures in this thesis were created by the author using IDL(R) or CorelDraw®. The image on the cover is Plate XI from "Experiments on the Refrangibility of the Invisible Rays of the Sun," by Sir William Herschel, published in Philosophical Transactions oj the Royal Society of London, Volume 90 (1800). Plate XI shows the apparatus Herschel used to discover infrared radiation. (Image @ the Royal Society.
We present the preliminary design of FTS-2, an imaging Fourier transform spectrometer (IFTS) for ... more We present the preliminary design of FTS-2, an imaging Fourier transform spectrometer (IFTS) for use with SCUBA-2, the second generation, wide-field, submillimetre camera currently under development for the James Clerk Maxwell Telescope (JCMT). This system, which is planned for operation at the start of 2007, will provide simultaneous broadband spectral imaging across both the 850 and 450 µm bands with variable resolution ranging from resolving powers of R ~10 to 5000. The spectrometer uses a folded Mach-Zehnder configuration and novel intensity beam dividers. The mechanical and optical design of FTS-2 as of the Critical Design Review stage of the project are discussed, along with the interfaces with SCUBA-2 and the JCMT.
Millimeter and Submillimeter Detectors for Astronomy II, 2004
We present the recent developments and current design and of an imaging Fourier transform spectro... more We present the recent developments and current design and of an imaging Fourier transform spectrometer (IFTS) for use with SCUBA-2, the second generation, wide-field, submillimetre camera currently under development for the James Clerk Maxwell Telescope (JCMT). The spectrometer will offer variable resolution with resolving powers ranging from R ~10 to 5000. The IFTS uses a folded Mach-Zehnder configuration with novel intensity beam dividers and dual input ports for continuous atmospheric cancellation. This system, which is planned for operation in 2006, will provide simultaneous, broadband, intermediate spectral resolution imaging across both the 850 and 450 µm bands. The optics, observing modes, and projected telescope performance of the IFTS are discussed.
Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy XI
The next generation of astronomical space-based far-infrared (FIR) missions require ultra-sensiti... more The next generation of astronomical space-based far-infrared (FIR) missions require ultra-sensitive spectroscopy as a diagnostic tool. These instruments use ultra-sensitive detector technologies to attain unprecedented levels of spectral observing sensitivity. The reception patterns of the individual detectors consist of individually coherent orthogonal field distributions, or equivalently, they are few-mode (5-20), to increase the spectral-spatial coupling to the astronomical source. However, the disadvantage of few-mode detectors is an increase in coupling to external (from the sky or warm telescope optics) and internal (from the instrument itself) straylight, which can greatly affect the measurement of the source spectrum. Therefore, understanding the spectral-spatial few-mode behaviour of these systems in detail, and developing verification and calibration strategies, are crucial to ensure that the science goals of these future mission are met. Since conventional modelling techniques are less suited to address this problem, we developed a modal framework to model, analyse, and address these issues. 1 In this paper, we use Herschel 's Spectral and Photometric Imaging REceiver (SPIRE) as a case study, because its optical design is representative for future FIR missions and illustrative to highlight calibration issues observed in-flight, while including straylight. Our analysis consist out of two part. In the first part, we use our modal framework to simulate the few-mode SPIRE Fourier Transform Spectrometer (FTS). In the second part, we carry out a end-to-end frequency-dependent partially coherent analysis of Herschel-SPIRE. These simulations offer a qualitative explanation for the few-mode behaviour observed in-flight. Furthermore, we use the Herschel-SPIRE case-study to demonstrate how the modelling framework can be used to support the design, verification and calibration of spectrometers for future FIR missions. The modal framework is not only limited to the spectrometers discussed, but it can be used to simulated a wide range of spectrometers, such as low-resolution gratings and high-spectral resolution Fabry-Pérot interferometers.
This proposal advocates for a collective science initiative within Canada to better understand th... more This proposal advocates for a collective science initiative within Canada to better understand the nature of interstellar dust through its entire life cycle. Interstellar dust grains (solid particles) are a fundamental probe of the Universe. Dust is present across multiple scales that probe the physical properties of (1) dense and diffuse clouds in the multi-phase ISM in galaxies, (2) the atmospheres of evolved stars, (3) the ejecta of stellar remnants, (4) circumstellar disks, and (5) the high-redshift universe. <br> <br> Even though dust is such a key component in how we perceive entire galaxies, characterize stellar evolution, and trace both star and planet formation, we don't have good physical and chemical constraints on the dust grains themselves. What are dust grains made out of? What is their size distribution? What is their structure? These questions are a key problem in using dust as a probe of the universe. These questions are also non-trivial, because dus...
Imaging applications at terahertz frequencies are, in general, limited to relatively low spatial ... more Imaging applications at terahertz frequencies are, in general, limited to relatively low spatial resolution due to the effects of diffraction. By using a subwavelength aperture in the near-field, however, it is possible to achieve subwavelength resolution, although low transmission through the aperture limits the sensitivity of this approach. Plasmonic lenses in the form of bullseye structures, which consist of a circular subwavelength aperture surrounded by concentric periodic corrugations, have demonstrated enhanced transmission, thereby increasing the utility of near-field imaging configurations. In this paper, the design, fabrication, and experimental performance of plasmonic lenses optimized for 300 GHz are discussed. While nanofabrication techniques are required for optical applications, microfabrication techniques are sufficient for terahertz applications. The process flow for fabricating a double-sided bullseye structure using a precision micromilling technique is described. Transmission and beam profile measurements using a customized terahertz testbed are presented.
Fourier Transform Spectroscopy/ Hyperspectral Imaging and Sounding of the Environment, 2005
We present the University of Lethbridge Transmission and Radiance Atmospheric Model (ULTRAM). A c... more We present the University of Lethbridge Transmission and Radiance Atmospheric Model (ULTRAM). A comparison with FASCODE is presented, along with several sample applications of ULTRAM. The source code is freely available and easily customized.
Proceedings of the International Astronomical Union, 2013
Herbig Ae/Be objects, like their lower mass counterparts T Tauri stars, are seen to form a stable... more Herbig Ae/Be objects, like their lower mass counterparts T Tauri stars, are seen to form a stable circumstellar disk which is initially gas-rich and could ultimately form a planetary system. We present Herschel SPIRE 460–1540 GHz spectra of five targets out of a sample of 13 young disk sources, showing line detections mainly due to warm CO gas.
We present the performance characteristics of a water vapour monitor that has been permanently de... more We present the performance characteristics of a water vapour monitor that has been permanently deployed at ESO's Paranal observatory as a part of the VISIR upgrade project. After a careful analysis of the requirements and an open call for tender, the Low Humidity and Temperature Profiling microwave radiometer (LHATPRO), manufactured by Radiometer Physics GmbH (RPG), has been selected. The unit measures several channels across the strong water vapour emission line at 183 GHz, necessary for resolving the low levels of precipitable water vapour (PWV) that are prevalent on Paranal (median ~2.5 mm). The unit comprises the above humidity profiler (183-191 GHz), a temperature profiler (51-58 GHz), and an infrared radiometer (~10 μm) for cloud detection. The instrument has been commissioned during a 2.5 week period in Oct/Nov 2011, by comparing its measurements of PWV and atmospheric profiles with the ones obtained by 22 radiosonde balloons. In parallel an IR radiometer (Univ. Lethbridge) has been operated, and various observations with ESO facility spectrographs have been taken. The RPG radiometer has been validated across the range 0.5-9 mm demonstrating an accuracy of better than 0.1 mm. The saturation limit of the radiometer is about 20 mm. Currently, the radiometer is being integrated into the Paranal infrastructure to serve as a high time-resolution monitor in support of VLT science operations. The water vapour radiometer's ability to provide high precision, high time resolution information on this important aspect of the atmosphere will be most useful for conducting IR observations with the VLT under optimal conditions.
This letter reports the discovery of excess emission at the position of the H I n=22-21 Rydberg t... more This letter reports the discovery of excess emission at the position of the H I n=22-21 Rydberg transition in submillimetre solar spectra taken at the extreme solar limb. This emission feature at 22.096+/-0.003 cm-1 shows significant limb brightening, reaching intensities of 11% above the adjacent spectral continuum with line shapes fitted best by Gaussian functions with widths of 0.018+/-0.004 cm-1. This measurement represents the highest-n Rydberg line of H I detected to date in the solar spectrum.
Submillimetre continuum radiation allows us to probe cold objects, particularly the earliest, dus... more Submillimetre continuum radiation allows us to probe cold objects, particularly the earliest, dusty phases of star formation, high-redshift galaxies and circumstellar disks. The submillimetre window gives a unique view of the physical and dynamical conditions in the neutral and molecular interstellar medium. In the next decade a combination of wide-field surveys with single-dish telescopes and targeted follow-up with ALMA and other facilities should enable rapid progress in answering questions about the origins of planetary systems, stars and galaxies.
Over the last 40 years enormous advances have been made in infrared astronomy. Virtually all of t... more Over the last 40 years enormous advances have been made in infrared astronomy. Virtually all of these can be traced to the use of space-based telescopes, which avoid the deleterious effects of the earth's atmosphere, and continued improvements in detector sensitivity and instrument design. Since its initial and modest contributions to previous infrared space astronomy missions, starting with ISO through to Herschel, Canada has grown in stature and is now recognized as a partner of choice by leading space agencies and scientific consortia embarking on the next generation of IR space astronomy missions. This white paper reviews the history of Canada's contributions to IR space astronomy missions and presents the case for Canadian participation in the ESA-JAXA SPICA mission, which has been selected as one of three finalists for ESA's fifth medium class mission, M5.<br> <br> Observations at far-infrared (FIR) wavelengths are optimal, not only for exploring galaxy...
Abstract. Submillimetre spectra taken near to the solar limb with a polarizing interferometer on ... more Abstract. Submillimetre spectra taken near to the solar limb with a polarizing interferometer on the James Clerk Maxwell Telescope have been compared with disk-centre spectra to reveal a limb-brightened feature whose peak intensity occurs at the predicted frequency of the n=20–19 Rydberg transition in H i at 29.622 cm −1. A shoulder on this peak, at 29.65 cm −1, has been tentatively assigned to the equivalent transition in Mg i. The H i line exhibits limb brightening of up to 9 % of the diskcentre continuum intensity. The intensity of the Mg i line is about half of the H i line intensity across the observed region near to the limb. Widths of the H i line are between 0.020 and 0.027 cm −1, smaller than predicted by current models of this line in the Sun’s spectrum. These measurements represent the highest-n Rydberg lines detected to date in the solar spectrum. The measured line intensity, line width, limb brightening and the relative heights of the contributions from H i and Mg i pla...
The Spectral and Photometric Imaging Receiver (SPIRE) is one of three scientific instruments onbo... more The Spectral and Photometric Imaging Receiver (SPIRE) is one of three scientific instruments onboard the European Space Agency's Herschel Space Observatory launched on 14 May 2009. The low to medium resolution spectroscopic capability of SPIRE is provided by an imaging Fourier transform spectrometer of the Mach-Zehnder configuration. Results from the in flight performance verification the instrument design specifications is reviewed.
OSA Optical Sensors and Sensing Congress 2021 (AIS, FTS, HISE, SENSORS, ES), 2021
This paper describes the development and status of a cryogenic, far-infrared, post- dispersed, po... more This paper describes the development and status of a cryogenic, far-infrared, post- dispersed, polarizing FTS (PDPFTS), a candidate instrument concept for the next generation of far- infrared astronomical space telescopes.
Monthly Notices of the Royal Astronomical Society, 2016
Dust grains play a key role in the physics of star-forming regions, even though they constitute o... more Dust grains play a key role in the physics of star-forming regions, even though they constitute only ∼1 % of the mass of the interstellar medium. The derivation of accurate dust parameters such as temperature (T d), emissivity spectral index (β) and column density requires broadband continuum observations at far-infrared wavelengths. We present Herschel-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 broadband 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 T d and β to vary as free parameters. This yields T d of 9.8±0.2 K, 15.6±0.5 K and 10.9±0.2 K and corresponding β of 2.6∓0.9, 0.8∓0.1 and 2.4∓0.8 for L1521E, L1521F and L1689B respectively. The derived core masses are 1.0±0.1, 0.10±0.01 and 0.49±0.05 M , respectively. The core mass/Jeans mass ratios for L1521E and L1689B exceed unity indicating that they are unstable to gravitational collapse, and thus prestellar cores. By comparison, the elevated temperature and gravitational stability of L1521F support previous arguments that this source is more evolved and likely a protostar.
The Blue Sky Transmission and Radiance Atmospheric Model (BTRAM) was developed in an effort to cr... more The Blue Sky Transmission and Radiance Atmospheric Model (BTRAM) was developed in an effort to create a radiative transfer model that was both fast and fully customisable by the user. A number of earlier radiative transfer models, such as FASCODE and MODTRAN, offer powerful simulation capabilities, but have interfaces that make it difficult to tailor the model to the specific needs of a user. BTRAM, developed in the Interactive Data Language (IDL®) [5], provides users with a straightforward interface that allows the efficient calculation of radiative transfer through custom atmospheric profiles or gas cells, from submillimetre to visible wavelengths, all at variable resolution. BTRAM also allows the user to convolve simulated spectra with custom instrumental line shapes, providing a more realistic simulation of instrumental performance. This paper discusses the radiative transfer calculations used in the BTRAM code and presents applications of BTRAM simulated spectra from the far-infrared/submillimetre through to the visible spectral region.
Space Telescopes and Instrumentation I: Optical, Infrared, and Millimeter, 2006
This thesis was typeset with BlgX using a modified version of the the University of Cali fornia P... more This thesis was typeset with BlgX using a modified version of the the University of Cali fornia PhD dissertation class file, ucthesis. els. Unless otherwise noted, all figures in this thesis were created by the author using IDL(R) or CorelDraw®. The image on the cover is Plate XI from "Experiments on the Refrangibility of the Invisible Rays of the Sun," by Sir William Herschel, published in Philosophical Transactions oj the Royal Society of London, Volume 90 (1800). Plate XI shows the apparatus Herschel used to discover infrared radiation. (Image @ the Royal Society.
We present the preliminary design of FTS-2, an imaging Fourier transform spectrometer (IFTS) for ... more We present the preliminary design of FTS-2, an imaging Fourier transform spectrometer (IFTS) for use with SCUBA-2, the second generation, wide-field, submillimetre camera currently under development for the James Clerk Maxwell Telescope (JCMT). This system, which is planned for operation at the start of 2007, will provide simultaneous broadband spectral imaging across both the 850 and 450 µm bands with variable resolution ranging from resolving powers of R ~10 to 5000. The spectrometer uses a folded Mach-Zehnder configuration and novel intensity beam dividers. The mechanical and optical design of FTS-2 as of the Critical Design Review stage of the project are discussed, along with the interfaces with SCUBA-2 and the JCMT.
Millimeter and Submillimeter Detectors for Astronomy II, 2004
We present the recent developments and current design and of an imaging Fourier transform spectro... more We present the recent developments and current design and of an imaging Fourier transform spectrometer (IFTS) for use with SCUBA-2, the second generation, wide-field, submillimetre camera currently under development for the James Clerk Maxwell Telescope (JCMT). The spectrometer will offer variable resolution with resolving powers ranging from R ~10 to 5000. The IFTS uses a folded Mach-Zehnder configuration with novel intensity beam dividers and dual input ports for continuous atmospheric cancellation. This system, which is planned for operation in 2006, will provide simultaneous, broadband, intermediate spectral resolution imaging across both the 850 and 450 µm bands. The optics, observing modes, and projected telescope performance of the IFTS are discussed.
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Papers by David Naylor