W. K. Gear
A5021323671- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Superconducting and THz Device Technology
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Astro and Planetary Science
- Cosmology and Gravitation Theories
- Astronomical Observations and Instrumentation
- Dark Matter and Cosmic Phenomena
- Particle Accelerators and Free-Electron Lasers
- Adaptive optics and wavefront sensing
- Solar and Space Plasma Dynamics
- Calibration and Measurement Techniques
- Gyrotron and Vacuum Electronics Research
- Atmospheric Ozone and Climate
- Scientific Research and Discoveries
- Neutrino Physics Research
- Geophysics and Gravity Measurements
- Spectroscopy and Laser Applications
- Computational Physics and Python Applications
- Particle accelerators and beam dynamics
Ollscoil na Gaillimhe – University of Galway
2021-2023
National University of Ireland
2020
Cardiff University
2009-2019
Netherlands Institute for Radio Astronomy
2005-2012
Royal Observatory
1990-2008
University of Wales Institute Cardiff
2004-2006
University of Wales
2003-2005
California Institute of Technology
2002
University College London
1998-2000
University of London
1985-1999
The Spectral and Photometric Imaging Receiver (SPIRE), is the Herschel Space Observatory`s submillimetre camera spectrometer. It contains a three-band imaging photometer operating at 250, 350 500 microns, an Fourier Transform Spectrometer (FTS) which covers simultaneously its whole range of 194-671 microns (447-1550 GHz). SPIRE detectors are arrays feedhorn-coupled bolometers cooled to 0.3 K. has field view 4' x 8', observed in three spectral bands. Its main mode scan-mapping, whereby...
view Abstract Citations (1139) References (51) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Models for high-frequency radio outbursts in extragalactic sources, with application to the early 1983 millimeter-to-infrared flare of 3C 273. Marscher, A. P. ; Gear, W. K. The present models compact source variability, reference mm-to-IR quasar 273, indicate that outburst spectrum's evolution is most easily explained if flaring component expanding. encompass...
The advent of sensitive sub-mm array cameras now allows a proper census dust-enshrouded massive star-formation in very distant galaxies, previously hidden activity to which even the faintest optical images are insensitive. We present deepest survey sky date, taken with SCUBA camera on James Clerk Maxwell Telescope and centred Hubble Deep Field. high source density found this image implies that is confusion-limited below flux 2 mJy. However, within central 80 arcsec radius independent...
SCUBA, the Submillimetre Common-User Bolometer Array, built by Royal Observatory Edinburgh for James Clerk Maxwell Telescope, is most versatile and powerful of a new generation submillimetre cameras.It combines sensitive dual-waveband imaging array with three-band photometer, sky-background limited emission from Mauna Kea atmosphere at all observing wavelengths 350 µm to 2 mm.The increased sensitivity size mean that SCUBA maps close 10,000 times faster than its single-pixel predecessor...
The Herschel Multi-tiered Extragalactic Survey (HerMES) is a legacy programme designed to map set of nested fields totalling ∼380 deg2. Fields range in size from 0.01 ∼20 deg2, using the Herschel-Spectral and Photometric Imaging Receiver (SPIRE) (at 250, 350 500 μm) Herschel-Photodetector Array Camera Spectrometer (PACS) 100 160 μm), with an additional wider component 270 deg2 SPIRE alone. These bands cover peak redshifted thermal spectral energy distribution interstellar dust thus capture...
We present total and polarized intensity images of 15 active galactic nuclei obtained with the Very Long Baseline Array at 7 mm wavelength 17 epochs from 1998 March to 2001 April. At some are accompanied by nearly simultaneous polarization measurements 3 mm, 1.35/0.85 optical wavelengths. Here we analyze define properties jets two radio galaxies, five BL Lac objects, eight quasars on angular scales ≳0.1 mas. determine apparent velocities 106 features in jets. For many derive Doppler factors...
We present the maps, source catalogue and number counts of largest, most complete unbiased extragalactic submillimetre survey ever undertaken: 850-micron SCUBA HAlf Degree Extragalactic Survey (SHADES). Using Submillimetre Common-User Bolometer Array (SCUBA) on James Clerk Maxwell Telescope (JCMT), SHADES mapped two separate regions sky: Subaru/XMM-Newton Deep Field (SXDF) Lockman Hole East (LH). These maps cover 720 square arcmin with an RMS noise level about 2 mJy have uncovered >100...
The Herschel Reference Survey is a guaranteed time key project and will be benchmark study of dust in the nearby universe. survey complement number other projects including large cosmological surveys that trace distant We use to produce images statistically-complete sample 323 galaxies at 250, 350 500 micron. volume-limited, containing sources with distances between 15 25 Mpc flux limits K-band minimize selection effects associated young high-mass stars introduce stellar mass. spans whole...
Dust emission around the nearby star Eridani has been imaged using a new submillimeter camera (the Submillimetre Common-User Bolometer Array at James Clerk Maxwell Telescope). At an 850 μm wavelength, ring of dust is seen peaking 60 AU from and with much lower inside 30 AU. The mass least ~0.01 M⊕ in dust, while upper limit 0.4 molecular gas imposed by CO observations. total comparable to estimated amount material, 0.04-0.3 M⊕, comets orbiting solar system. most probable origin structure...
We present the first results of a deep unbiased submillimeter survey carried out at 450 and 850 μm. detected 12 sources μm greater than 3 σ level, giving surface density with S850μm>2.8 mJy 0.49 ± 0.16 arcmin-2. If replicated over sky, our would generate background 9.6 × 10−11 W m-2 sr-1, which is ≃20% value measured by Far-Infrared Absolute Spectrophotometer (FIRAS) significant fraction total radiation produced stars. This implies, through connection between metallicity radiation, that all...
Identifications are sought for 12 submillimeter sources detected in a deep survey. Six securely identified, two have probable identifications, and four remain unidentified with IAB > 25. Spectroscopic estimated photometric redshifts indicate that of the z < 1 3, remaining empty-field probably lying at 3. The spectral energy distributions as defined by measurements or upper limits to flux densities 8000 Å, 15, 450, 850 μm, 6 cm, consistent high-extinction starbursts such Arp 220. far-IR...
We report on the sensitivity of SPIRE photometers <i>Herschel<i/> Space Observatory. Specifically, we measure confusion noise from observations taken during science demonstration phase Multi-tiered Extragalactic Survey. Confusion is defined to be spatial variation sky intensity in limit infinite integration time, and found consistent among different fields our survey at level 5.8, 6.3 6.8 mJy/beam 250, 350 500 <i>μ<i/>m, respectively. These results, together with measured instrument noise,...
The blazar 3C 279, one of the brightest identified extragalactic objects in γ-ray sky, underwent a large (factor ~10 amplitude) flare γ-rays toward end 3 week pointing by Compton Gamma Ray Observatory (CGRO), 1996 January-February. peak represents highest intensity ever recorded for this object. During high state, extremely rapid variability was seen, including an increase factor 2.6 ~8 hr, which strengthens case relativistic beaming. Coordinated multifrequency observations were carried out...
We set out to determine the ratio, q(IR), of rest-frame 8-1000um flux, S(IR), monochromatic radio S(1.4GHz), for galaxies selected at far-IR and wavelengths, search signs that ratio evolves with redshift, luminosity or dust temperature, identify any far-IR-bright outliers - useful laboratories exploring why far-IR/radio correlation is generally so tight when prevailing theory suggests variations are almost inevitable. use flux-limited 250-um 1.4-GHz samples, obtained in GOODS-N using...
We present an improved analysis of the final dataset from QUaD experiment. Using technique to remove ground contamination, we double effective sky area and hence increase precision our CMB power spectrum measurements by ~30% versus that previously reported. In addition, have modeling instrument beams reduced absolute calibration uncertainty 5% 3.5% in temperature. The robustness results is confirmed through extensive jackknife tests way agreement find between two fully independent pipelines....
We present Herschel observations of 62 early-type galaxies (ETGs), including 39 morphologically classified as S0+S0a and 23 ellipticals using SPIRE at 250, 350, 500 μm part the volume-limited Reference Survey (HRS). detect dust emission in 24% 62% S0s. The mean temperature is 〈Td〉 = 23.9 ± 0.8 K, warmer than that found for late-type Virgo Cluster. mass entire detected sample logMd 6.1 0.1 M☉ with a dust-to-stellar-mass ratio log(Md/M*) −4.3 0.1. Including non-detections, these parameters are...
Emission at far-infrared wavelengths makes up a significant fraction of the total light detected from galaxies over age Universe. Herschel provides an opportunity for studying peak wavelength their emission. Our aim is to provide benchmark models galaxy population evolution and test pre-existing galaxies. With Multi-tiered Extra-galactic survey, HerMES, we have observed number fields different areas sensitivity using SPIRE instrument on Herschel. We determined counts down ~20 mJy....
Using the 3.5-m Herschel Space Observatory, imaging photometry of Cas A has been obtained in six bands between 70 um and 500 with PACS SPIRE instruments, angular resolutions ranging from 6 to 37". In outer regions remnant 70-um image resembles 24-um Spitzer image, emission attributed same warm dust component, located reverse shock region. At longer wavelengths, three are increasingly dominated by cold interstellar knots filaments, particularly across central, western southern parts remnant....
Whether supernovae are major sources of dust in galaxies is a long-standing debate. We present infrared and submillimeter photometry spectroscopy from the Herschel Space Observatory Crab Nebula between 51 670 μm as part Mass Loss Evolved StarS program. compare emission detected with multiwavelength data including millimeter, radio, mid-infrared, archive optical images. carefully remove synchrotron component using Planck fluxes measured same epoch. The contribution line removed combined...
The <i>Herschel<i/> Space Observatory enables us to accurately measure the bolometric output of starburst galaxies and active galactic nuclei (AGN) by directly sampling peak their far-infrared (IR) emission. Here we examine whether spectral energy distribution (SED) dust temperature have strongly evolved over last 80% age Universe. We discuss possible consequences for determination star-formation rates (SFR) any evidence a major change in properties. use deep extragalactic surveys from 100...
We present an analysis of the dust and gas in Andromeda, using Herschel images sampling entire far-infrared peak. fit a modified-blackbody model to ∼4000 quasi-independent pixels with spatial resolution ∼140 pc find that variable dust-emissivity index (β) is required data. no significant long-wavelength excess above this model, suggesting there cold component. show gas-to-dust ratio varies radially, increasing from ∼20 center ∼70 star-forming ring at 10 kpc, consistent metallicity gradient....