Search Publications
The Herschel Multi-tiered Extragalactic Survey: HerMES
Altieri, B.; Aussel, H.; Elbaz, D. +101 more
The Herschel Multi-tiered Extragalactic Survey (HerMES) is a legacy programme designed to map a set of nested fields totalling ∼380 deg2. Fields range in size from 0.01 to ∼20 deg2, using the Herschel-Spectral and Photometric Imaging Receiver (SPIRE) (at 250, 350 and 500 µm) and the Herschel-Photodetector Array Camera a…
Intrinsic disc emission and the soft X-ray excess in active galactic nuclei
Done, Chris; Ward, M.; Jin, C. +2 more
Narrow-line Seyfert 1 (NLS1) galaxies have low-mass black holes and mass accretion rates close to (or exceeding) Eddington, so a standard blackbody accretion disc should peak in the extreme ultraviolet. However, the lack of true absorption opacity in the disc means that the emission is better approximated by a colour temperature corrected blackbod…
Scaling relations for galaxy clusters in the Millennium-XXL simulation
White, S. D. M.; Baugh, C. M.; Frenk, C. S. +3 more
We present a very large high-resolution cosmological N-body simulation, the Millennium-XXL or MXXL, which uses 303 billion particles to represent the formation of dark matter structures throughout a 4.1 Gpc box in a Λ cold dark matter cosmology. We create sky maps and identify large samples of galaxy clusters using surrogates for four different ob…
Semi-analytic modelling of the extragalactic background light and consequences for extragalactic gamma-ray spectra
Somerville, Rachel S.; Primack, Joel R.; Domínguez, Alberto +1 more
Attenuation of high-energy gamma-rays by pair production with ultraviolet, optical and infrared (IR) extragalactic background light (EBL) photons provides a link between the history of galaxy formation and high-energy astrophysics. We present results from our latest semi-analytic models (SAMs), which employ the main ingredients thought to be impor…
Ubiquitous equatorial accretion disc winds in black hole soft states
Ponti, G.; Fender, R. P.; Neilsen, J. +3 more
High-resolution spectra of Galactic black holes (GBHs) reveal the presence of highly ionized absorbers. In one GBH, accreting close to the Eddington limit for more than a decade, a powerful accretion disc wind is observed to be present in softer X-ray states and it has been suggested that it can carry away enough mass and energy to quench the radi…
Using the Bright Ultrahard XMM-Newton survey to define an IR selection of luminous AGN based on WISE colours
Stern, D.; Barcons, X.; Blain, A. +7 more
We present a highly complete and reliable mid-infrared (MIR) colour selection of luminous active galactic nucleus (AGN) candidates using the 3.4, 4.6 and 12 µm bands of the Wide-field Infrared Survey Explorer (WISE) survey. The MIR colour wedge was defined using the wide-angle Bright Ultrahard XMM-Newton survey (BUXS), one of the largest com…
A simplified view of blazars: clearing the fog around long-standing selection effects
D'Elia, V.; Polenta, G.; Giommi, P. +3 more
We propose a scenario where blazars are classified into flat-spectrum radio quasars (FSRQs), BL Lacertae (BL Lac) objects, low-synchrotron, or high-synchrotron peaked objects according to a varying mix of the Doppler-boosted radiation from the jet, the emission from the accretion disc, the broad-line region, and the light from the host galaxy. In …
The chemical diversity of exo-terrestrial planetary debris around white dwarfs
Gänsicke, B. T.; Breedt, E.; Koester, D. +3 more
We present Hubble Space Telescope (HST) ultraviolet spectroscopy of the white dwarfs PG 0843+516, PG 1015+161, SDSS 1228+1040, and GALEX 1931+0117, which accrete circumstellar planetary debris formed from the destruction of asteroids. Combined with optical data, a minimum of five and a maximum of 11 different metals are detected in their photosphe…
Updating quasar bolometric luminosity corrections
Shang, Zhaohui; Brotherton, Michael S.; Runnoe, Jessie C.
Bolometric corrections are used in quasar studies to quantify total energy output based on a measurement of a monochromatic luminosity. First, we enumerate and discuss the practical difficulties of determining such corrections, then we present bolometric luminosities between 1 µm and 8 keV rest frame and corrections derived from the detailed…
A Gaussian process framework for modelling instrumental systematics: application to transmission spectroscopy
Aigrain, S.; Pont, F.; Gibson, N. P. +3 more
Transmission spectroscopy, which consists of measuring the wavelength-dependent absorption of starlight by a planet's atmosphere during a transit, is a powerful probe of atmospheric composition. However, the expected signal is typically orders of magnitude smaller than instrumental systematics and the results are crucially dependent on the treatme…