Search Publications
On characterizing the variability properties of X-ray light curves from active galaxies
Vaughan, S.; Uttley, P.; Warwick, R. S. +1 more
We review some practical aspects of measuring the amplitude of variability in `red noise' light curves typical of those from active galactic nuclei (AGN). The quantities commonly used to estimate the variability amplitude in AGN light curves, such as the fractional rms variability amplitude, Fvar, and excess variance, σ2…
The chemical compositions of Galactic disc F and G dwarfs
Lambert, David L.; Allende Prieto, Carlos; Reddy, Bacham E. +1 more
Photospheric abundances are presented for 27 elements from carbon to europium in 181 F and G dwarfs from a differential local thermodynamic equilibrium (LTE) analysis of high-resolution and high signal-to-noise ratio spectra. Stellar effective temperatures (Teff) were adopted from an infrared flux method calibration of Strömgren photome…
Quasars, their host galaxies and their central black holes
McLure, R. J.; Dunlop, J. S.; Hughes, D. H. +3 more
We present the final results from our deep Hubble Space Telescope (HST) imaging study of the host galaxies of radio-quiet quasars (RQQs), radio-loud quasars (RLQs) and radio galaxies (RGs). We describe and analyse new Wide Field & Planetary Camera 2 (WFPC2) R-band observations for 14 objects, which when combined with the first tranche of HST i…
A high-velocity ionized outflow and XUV photosphere in the narrow emission line quasar PG1211+143
O'Brien, P. T.; King, A. R.; Reeves, J. N. +3 more
We report on the analysis of a ~60-ks XMM-Newton observation of the bright, narrow emission line quasar PG1211+143. Absorption lines are seen in both European Photon Imaging Camera and Reflection Grating Spectrometer spectra corresponding to H- and He-like ions of Fe, S, Mg, Ne, O, N and C. The observed line energies indicate an ionized outflow ve…
The Cosmic Lens All-Sky Survey - II. Gravitational lens candidate selection and follow-up
Pearson, T. J.; McKean, J. P.; Blandford, R. D. +19 more
We report the final results of the search for gravitationally lensed flat-spectrum radio sources found in the combination of CLASS (Cosmic Lens All-Sky Survey) and JVAS (Jodrell Bank VLA Astrometric Survey). VLA (Very Large Array) observations of 16503 sources have been made, resulting in the largest sample of arcsec-scale lens systems available. …
Shapelets - I. A method for image analysis
Refregier, Alexandre
We present a new method for the analysis of images, a fundamental task in observational astronomy. It is based on the linear decomposition of each object in the image into a series of localized basis functions of different shapes, which we call `shapelets'. A particularly useful set of complete and orthonormal shapelets is that consisting of weigh…
Surface brightness profiles and structural parameters for 53 rich stellar clusters in the Large Magellanic Cloud
Mackey, A. D.; Gilmore, G. F.
We have compiled a pseudo-snapshot data set of two-colour observations from the Hubble Space Telescope archive for a sample of 53 rich LMC clusters with ages of 106-1010 yr. We present surface brightness profiles for the entire sample, and derive structural parameters for each cluster, including core radii, and luminosity and…
Star cluster formation and disruption time-scales - I. An empirical determination of the disruption time of star clusters in four galaxies
Lamers, H. J. G. L. M.; Boutloukos, S. G.
We have derived the disruption times of star clusters from cluster samples of four galaxies, M51, M33, the Small Magellanic Cloud (SMC) and the solar neighbourhood. If the disruption time of clusters in a galaxy depends only on their initial mass as tdis(yr) =t4dis(Mcl/104 Msolar)
The iron line in MCG-6-30-15 from XMM-Newton: evidence for gravitational light bending?
Vaughan, S.; Fabian, A. C.
The lack of variability of the broad iron line seen in the Seyfert 1 galaxy MCG-6-30-15 is studied using the EPIC pn data obtained from a 2001 observation of 325 ks, during which the count rate from the source varied by a factor of 5. The spectrum of 80 ks of data from when the source was bright, using the lowest 10 ks as background, is well fitte…
Lyman break galaxies and the star formation rate of the Universe at z~ 6
Bunker, Andrew J.; McMahon, Richard G.; Stanway, Elizabeth R.
We determine the space density of UV-luminous starburst galaxies at z~ 6 using deep HST ACS SDSS-i' (F775W) and SDSS-z' (F850LP) and VLT ISAAC J and Ks band imaging of the Chandra Deep Field South. We find eight galaxies and one star with (i'-z') > 1.5 to a depth of z'AB= 25.6 (an 8σ detection in each of the 3 available AC…