Ian Robson

Bio: Ian Robson is an academic researcher from UK Astronomy Technology Centre. The author has contributed to research in topics: James Clerk Maxwell Telescope & Submillimetre astronomy. The author has an hindex of 11, co-authored 24 publications receiving 862 citations.

Submillimetre images of dusty debris around nearby stars

Abstract: Indirect detections of massive — presumably Jupiter-like — planets orbiting nearby Sun-like stars have recently been reported1,2. Rocky, Earth-like planets are much more difficult to detect, but clues to their possible existence can nevertheless be obtained from observations of the circumstellar debris disks of dust from which they form. The presence of such disks has been inferred3 from excess far-infrared emission but, with the exception of beta Pictoris4, it has proved difficult to image these structures directly as starlight dominates the faint light scattered by the dust5. A more promising approach is to attempt to image the thermal emission from the dust grains at submillimetre wavelengths6,7. Here we present images of such emission around Fomalhaut, beta Pictoris and Vega. For each star, dust emission is detected from regions comparable in size to the Sun's Kuiper belt of comets. The total dust mass surrounding each star is only a few lunar masses, so any Earth-like planets present must already have formed. The presence of the central cavity, approximately the size of Neptune's orbit, that we detect in the emission from Fomalhaut may indeed be the signature of such planets.

Submillimetre observations of z > 6 quasars

Abstract: We report on submillimetre (submm) observations of three high-redshift quasars (z > 6) made using the SCUBA camera on the James Clerk Maxwell Telescope (JCMT). Only one of the sample was detected (>10σ significance) at 850 µm ‐ SDSS J1148+5251 (z = 6.43). It was also detected at 450 µ m( >3σ significance), one of the few quasars at z > 4 for which this has been the case. In combination with existing millimetric data, the 850- and 450-µm detections allow us to place limits on the temperature of the submm-emitting dust. The dust temperature is of no trivial importance given the high redshift of the source, since a cold temperature would signify a large mass of dust to be synthesized in the little time available (as an extreme upper limit in only 0.9 Gyr since z =∞ ). We find, however, that the combined millimetre and submm data for the source cannot simply be characterized using the single-temperature greybody fit that has been used at lower redshifts. We discuss the results of the observing and modelling, and speculate as to the origin of the deviations.

SCUBA-2: a 10,000-pixel submillimeter camera for the James Clerk Maxwell Telescope

Abstract: SCUBA-2 is an innovative 10,000 pixel submillimeter camera due to be delivered to the James Clerk Maxwell Telescope in late 2006. The camera is expected to revolutionize submillimeter astronomy in terms of the ability to carry out wide-field surveys to unprecedented depths addressing key questions relating to the origins of galaxies, stars and planets. This paper presents an update on the project with particular emphasis on the laboratory commissioning of the instrument. The assembly and integration will be described as well as the measured thermal performance of the instrument. A summary of the performance results will be presented from the TES bolometer arrays, which come complete with in-focal plane SQUID amplifiers and multiplexed readouts, and are cooled to 100mK by a liquid cryogen-free dilution refrigerator. Considerable emphasis has also been placed on the operating modes of the instrument and the "common-user" aspect of the user interface and data reduction pipeline. These areas will also be described in the paper.

The 1997 Outburst of AO 0235+164: Evidence for a Microlensing Event?

Abstract: We present multiwavelength observations of AO 0235+164 made during a 5 mag outburst in 1997. Detection of the outburst at the observatory of the South Eastern Association for Research in Astronomy prompted a concerted effort by several observatories to monitor the source in the R band. We present V-, R-, and I-band photometry, as well as contemporaneous 850 μm and X-ray measurements. We also use radio measurements from the University of Michigan's World Wide Web site in our analysis. We find that the source varies nearly simultaneously over 6 decades in frequency during this outburst and examine the possibility that the outburst was a result of a microlensing event. The duration of the outburst was on the order of 800 days, and the maximum luminosity was approximately 9.86 × 1047 ergs s-1 (assuming no relativistic beaming). We also analyze the long-term optical light curve and find that, although there is still no evidence for periodicity, the variations are interesting: the timescales between pairs of outbursts are remarkably similar. We suggest that the multifrequency behavior of the 1997 outburst is consistent with microlensing scenarios, while observations of previous outbursts suggest they were not consistent with gravitational microlensing.

SCUBA-2: a large-format TES array for submillimetre astronomy

Abstract: SCUBA-2, which replaces the Submillimetre Common User Bolometer Array (SCUBA) (Mon. Not. R. Astron. Soc. 303 (1999) 659) on the James Clerk Maxwell telescope in 2006, will be the first CCD-like array for submillimeter astronomy. Unlike previous detectors which have used discrete bolometers, SCUBA-2 has two DC-coupled, monolithic, filled arrays with a total of 10,000 bolometers. It will offer simultaneous imaging of an 8A—8 arcmin field of view at wavelengths of 850 and 450 I¼m. SCUBA-2 is expected to have a huge impact on the study of galaxy formation and evolution in the early Universe as well as star and planet formation in our own Galaxy. Mapping the sky to the same S/N up to 1000 times faster than SCUBA, it will also act as a pathfinder for the new submillimetre interferometers such as ALMA. SCUBA-2's absorber-coupled pixels use superconducting transition edge sensors (Ph.D. Thesis, Stanford, 1995) operating at 120 mK for photon noise limited performance. The monolithic silicon detector arrays are deep-etched by the Bosch process to isolate the pixels on silicon nitride membranes (Nucl. Instr. and Meth. A, these proceedings). Electrical connections are made through indium bump bonds to a backplane that incorporates a SQUID time-domain multiplexer. We describe the key technologies that make SCUBA-2 possible and give an update on the considerable progress in the detector development and instrument design that has taken place over the last 2 years

Materials for terahertz science and technology

Abstract: Terahertz spectroscopy systems use far-infrared radiation to extract molecular spectral information in an otherwise inaccessible portion of the electromagnetic spectrum. Materials research is an essential component of modern terahertz systems: novel, higher-power terahertz sources rely heavily on new materials such as quantum cascade structures. At the same time, terahertz spectroscopy and imaging provide a powerful tool for the characterization of a broad range of materials, including semiconductors and biomolecules.

Evolution of Debris Disks

Abstract: Circumstellar dust exists around several hundred main sequence stars. For the youngest stars, that dust could be a remnant of the protoplanetary disk. Mostly it is inferred to be continuously replenished through collisions between planetesimals in belts analogous to the Solar System’s asteroid and Kuiper belts, or in collisions between growing protoplanets. The evolution of a star’s debris disk is indicative of the evolution of its planetesimal belts and may be influenced by planet formation processes, which can continue throughout the first gigayear as the planetary system settles to a stable configuration and planets form at large radii. Evidence for that evolution comes from infrared photometry of large numbers of debris disks, providing snapshots of the dust present at different evolutionary phases, as well as from images of debris disk structure. This review describes the theoretical framework within which debris disk evolution takes place and shows how that framework has been constrained by observations.

Molecular Gas at High Redshift

Abstract: ▪ Abstract The Early Universe Molecular Emission Line Galaxies (EMGs) are a population of galaxies with only 36 examples that hold great promise for the study of galaxy formation and evolution at high redshift. The classification, luminosity of molecular line emission, molecular mass, far-infrared (FIR) luminosity, star formation efficiency, morphology, and dynamical mass of the currently known sample are presented and discussed. The star formation rates derived from the FIR luminosity range from about 300 to 5000 M⊙ year −1 and the molecular mass from 4 × 109 to 1 × 1011 M⊙. At the lower end, these star formation rates, gas masses, and diameters are similar to those of local ultraluminous infrared galaxies and represent starbursts in centrally concentrated disks, sometimes, but not always, associated with active galactic nuclei. The evidence for large (>5 kpc) molecular disks is limited. Morphology and several high angular resolution images suggest that some EMGs are mergers with a massive molecular inte...

Young Stars Near the Sun

Abstract: ▪ Abstract Until the late 1990s the rich Hyades and the sparse UMa clusters were the only coeval, comoving concentrations of stars known within 60 pc of Earth. Both are hundreds of millions of years old. Then beginning in the late 1990s the TW Hydrae Association, the Tucana/Horologium Association, the β Pictoris Moving Group, and the AB Doradus Moving Group were identified within ∼60 pc of Earth, and the η Chamaeleontis cluster was found at 97 pc. These young groups (ages 8–50 Myr), along with other nearby, young stars, will enable imaging and spectroscopic studies of the origin and early evolution of planetary systems.