Walter K. Gear

Learn More
We describe the QUaD experiment, a millimeter-wavelength polarimeter designed to observe the cosmic microwave background (CMB) from a site at the South Pole. The experiment comprises a 2.64 m Cassegrain telescope equipped with a cryogenically cooled receiver containing an array of 62 polarization-sensitive bolometers. The focal plane contains pixels at two(More)
Blazars are the most extreme active galactic nuclei. They possess oppositely directed plasma jets emanating at near light speeds from accreting supermassive black holes. According to theoretical models, such jets are propelled by magnetic fields twisted by differential rotation of the black hole's accretion disk or inertial-frame-dragging ergosphere. The(More)
We present total and polarized intensity images of 15 active galactic nuclei obtained with the Very Long Baseline Array at 7mmwavelength at 17 epochs from 1998March to 2001 April. At some epochs the images are accompanied by nearly simultaneous polarizationmeasurements at 3mm, 1.35/0.85mm, and optical wavelengths. Herewe analyze the 7 mm images to define(More)
SCUBA, the Submillimetre Common-User Bolometer Array, built by the Royal Observatory Edinburgh for the James Clerk Maxwell Telescope, is the most versatile and powerful of a new generation of submillimetre cameras. It combines a sensitive dualwaveband imaging array with a three-band photometer, and is sky-background limited by the emission from the Mauna(More)
The extragalactic background light at far-infrared wavelengths comes from optically faint, dusty, star-forming galaxies in the Universe with star formation rates of a few hundred solar masses per year. These faint, submillimetre galaxies are challenging to study individually because of the relatively poor spatial resolution of far-infrared telescopes.(More)
Modern far-infrared and submillimeter instruments require large-format arrays. We consider the relative performance of filled-array (bare pixel) and feedhorn-coupled architectures for bolometer focal planes. Based on typical array parameters, we quantify the relative observing speeds and comment on the merits of the different architectures. Filled arrays(More)
We report results from the second and third seasons of observation with the QUaD experiment. Angular power spectra of the cosmic microwave background are derived for both temperature and polarization at both 100 GHz and 150 GHz, and as cross-frequency spectra. All spectra are subjected to an extensive set of jackknife tests to probe for possible systematic(More)
We present maps, source catalogue and number counts of the largest, most complete and unbiased extragalactic submillimetre survey: the 850-μm SCUBA Half-Degree Extragalactic ⋆E-mail: C © 2006 The Authors. Journal compilation C © 2006 RAS at U n iv esity o f S u ssex o n Ju n e 9 , 2 0 1 4 h tp //m n rs.o x fo rd jo u rn as.o rg / D o w(More)
We present the first results of a deep unbiased submillimetre survey carried out at 450 and 850μm. We detected 12 sources at 850 μm, giving a surface density of sources with S850μm > 2.8 mJy of 0.49± 0.16 arcmin . The sources constitute 20-30% of the background radiation at 850μm and thus a significant fraction of the entire background radiation produced by(More)