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The correlated radio and optical asymmetries of powerful radio galaxies

We present radio continuum and polarization maps of four ‘classical double’ radio galaxies, overlaid on optical emission-line images. The sources (3C 247, 263.1, 280 and 299) are all small, powerful and distant (with $D \lt 200 \,\text kpc, {P}_{178} \gt {10}^{26.8}\,\text {W}\,\text {Hz}^{-1} \text {sr}^{-1},0.37 \lt z \lt 1.0$). In three cases we find that the emission-line gas...

Spectral index and depolarization asymmetry in powerful radio sources

In a sample of high-luminosity 3C radio sources, a strong correlation between spectral index and depolarization has been found: the lobe which is less depolarized has the flatter spectrum in 12 out of 13 cases. We compare this result with that of Garrington et al. and Laing, who found that the less-depolarized lobe is associated with the presence of a jet on the same side of the...

Measuring the Hubble constant from Ryle Telescope and X-ray observations, with application to Abell 1413

We describe our methods for measuring the Hubble constant from Ryle Telescope (RT) interferometric observations of the Sunyaev–Zel'dovich (SZ) effect from a galaxy cluster and observation of the cluster X-ray emission. We analyse the error budget in this method: as well as radio and X-ray random errors, we consider the effects of clumping and temperature differences in the...

Spectral ageing in a sample of 14 high-luminosity double radio sources

We use multifrequency observations of a sample of 14 high-luminosity 3C double radio sources in a discussion of their structures and spectral properties. The observations were made with the VLA at 1.4, 5 and 15 GHz and have resolutions of 0.4 or 1.2 arcsec. We interpret the spectra in terms of the ageing of the electron population, as in the related study by Alexander & Leahy...

G64.5+0.9: a new shell supernova remnant with unusual central emission*

We present observations between 1.4 and 18 GHz confirming that G64.5+0.9 is a new Galactic shell supernova remnant, using the Very Large Array and the Arcminute Microkelvin Imager. The remnant is a shell ≃8 arcmin in diameter with a spectral index of α= 0.47 ± 0.03 (with α defined such that flux density S varies with frequency ν as S∝ν−α). There is also emission near the centre...

AMI observations of northern supernova remnants at 14–18 GHz*

We present observations between 14.2 and 17.9 GHz of 12 reported supernova remnants (SNRs) made with the Arcminute Microkelvin Imager Small Array (AMI SA). In conjunction with data from the literature at lower radio frequencies, we determine spectra of these objects. For well-studied SNRs (Cas A, Tycho's SNR, 3C 58 and the Crab Nebula), the results are in good agreement with...

A study of the Crab Nebula at 2.7 GHz with an angular resolution 3.7 × 10 arcsec – I. The observations

The Crab Nebula has been observed with the Cambridge 5-km radio telescope at a frequency of 2.695 GHz, giving an angular resolution of 3.7 × 10 arcsec. Maps are presented showing total intensity and linear polarization. The nebula has a filamentary structure at this wavelength, strikingly similar to that seen in optical line emission. An upper limit of 0.1 per cent is placed on...

Detection of the Sunyaev–Zel'dovich effect in Abell 773

We have observed the cluster Abell 773 with the Ryle Telescope at 15 GHz, and have measured a decrement in the cosmic microwave background radiation (CMB) of $-590 \pm 116 \mu\enspace \text {Jy}\enspace \text {beam}^{-1}$, due to the Sunyaev- Zel'dovich (S–Z) effect. On reasonable assumptions about the structure of the cluster atmosphere, this implies a central temperature...

Very Small Array observations of the Sunyaev–Zel'dovich effect in nearby galaxy clusters

We present Very Small Array (VSA) observations (centred on ≈34 GHz) on scales ≈20 arcmin towards a complete, X-ray flux-limited sample of seven clusters at redshift z < 0.1. Four of the clusters have significant Sunyaev–Zel'dovich (SZ) detections in the presence of cosmic microwave background (CMB) primordial anisotropy. For all seven, we use a Bayesian Markov Chain Monte Carlo...

A resolved image of the Sunyaev-Zel'dovich effect in Abell 1413

Following observations of the cluster Abell 1413 with the Ryle Telescope (RT ) at 15 GHz, we report the detection of a resolved decrement in the cosmic microwave background arising from the Sunyaev-Zel'dovich (S-Z) effect with a significance of 8 a. The position and shape of the S-Z decrement are in good agreement with the X-ray image from the ROSAT satellite. Because of the...

The structure and dynamics of two tailed sources in cluster 0648 + 19

Observations at five radio frequencies are used to determine the structure and spectra of a complex region in the direction 0648 + 19. We show that it consists of three separate radio sources; two tailed sources in one cluster, and an unrelated classical double. We have used spectral-ageing calculations to derive ages and velocities for the two tailed sources. Combining these...

Detection of cosmic microwave background structure in a second field with the Cosmic Anisotropy Telescope

We describe observations at frequencies near 15 GHz of the second 2×2 deg2 field imaged with the Cambridge Cosmic Anisotropy Telescope (CAT). After the removal of discrete radio sources, structure is detected in the images on characteristic scales of about half a degree, corresponding to spherical harmonic multipoles in the range ℓ≈330–680. A Bayesian analysis confirms that the...

A search for primordial anisotropies in the cosmic microwave background radiation: first observations at 13.5 GHz with the Cosmic Anisotropy Telescope

We report the first observations of the cosmic microwave background radiation (CMBR) at 13.5 GHz made with the Cosmic Anisotropy Telescope (CAT) near Cambridge. After removal of foreground radio sources brighter than 10 mJy, using the Ryle Telescope (RT), the map shows evidence for residual structure on a scale of approximately 1/2° with an rms variation of 18 mJy. We intend to...

High-sensitivity measurements of the cosmic microwave background power spectrum with the extended Very Small Array

We present deep Ka-band (ν≈ 33 GHz) observations of the cosmic microwave background (CMB) made with the extended Very Small Array (VSA). This configuration produces a naturally weighted synthesized FWHM beamwidth of ∼11 arcmin, which covers an ℓ range of 300 to 1500. On these scales, foreground extragalactic sources can be a major source of contamination to the CMB anisotropy...

8C1435+635: a radio galaxy at z = 4.25

Radio galaxies at redshift z > 4 have proved to be very elusive. By searching for objects with unusual radio spectra between 38 and 4850 MHz, and following up with blind spectroscopy, we have discovered the first radio galaxy known with z > 4, 8C1435 + 635. In this paper we present our observations, discuss the evidence for the redshift, and compare the radio properties of 8Cl435...