Search Publications
The evolution of the X-ray luminosity functions of unabsorbed and absorbed AGNs out to z∼ 5
Georgakakis, A.; Nandra, K.; Aird, J. +3 more
We present new measurements of the evolution of the X-ray luminosity functions (XLFs) of unabsorbed and absorbed active galactic nuclei (AGNs) out to z ∼ 5. We construct samples containing 2957 sources detected at hard (2-7 keV) X-ray energies and 4351 sources detected at soft (0.5-2 keV) energies from a compilation of Chandra surveys supplemented…
The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters - V. Constraints on formation scenarios
Dalessandro, E.; Salaris, M.; Anderson, J. +16 more
We build on the evidence provided by our Legacy Survey of Galactic globular clusters (GC) to submit to a crucial test four scenarios currently entertained for the formation of multiple stellar generations in GCs. The observational constraints on multiple generations to be fulfilled are manifold, including GC specificity, ubiquity, variety, predomi…
Properties of AGN coronae in the NuSTAR era
Fabian, A. C.; Reynolds, C. S.; Lohfink, A. +3 more
The focusing optics of NuSTAR have enabled high signal-to-noise ratio spectra to be obtained from many X-ray bright active galactic nuclei (AGN) and galactic black hole binaries (BHB). Spectral modelling then allows robust characterization of the spectral index and upper energy cutoff of the coronal power-law continuum, after accounting for reflec…
Weighing the giants - IV. Cosmology and neutrino mass
Kelly, Patrick L.; Allen, Steven W.; Ebeling, Harald +14 more
We employ robust weak gravitational lensing measurements to improve cosmological constraints from measurements of the galaxy cluster mass function and its evolution, using X-ray selected clusters detected in the ROSAT All-Sky Survey. Our lensing analysis constrains the absolute mass scale of such clusters at the 8 per cent level, including both st…
The first ultraviolet quasar-stacked spectrum at z ≃ 2.4 from WFC3
Vignali, C.; Lusso, E.; Prochaska, J. X. +4 more
The ionizing continuum from active galactic nuclei is fundamental for interpreting their broad emission lines and understanding their impact on the surrounding gas. Furthermore, it provides hints on how matter accretes on to supermassive black holes. Using Hubble Space Telescope's Wide Field Camera 3, we have constructed the first stacked ultravio…
The formation of massive, compact galaxies at z = 2 in the Illustris simulation
van Dokkum, Pieter; Kriek, Mariska; Wellons, Sarah +13 more
Massive, quiescent galaxies at high redshift have been found to be considerably more compact than galaxies of similar mass in the local universe. How these compact galaxies formed has yet to be determined, though several progenitor populations have been proposed. Here we investigate the formation processes and quantify the assembly histories of su…
Filament identification through mathematical morphology
Koch, Eric W.; Rosolowsky, Erik W.
We present a new algorithm for detecting filamentary structure FILFINDER. The algorithm uses the techniques of mathematical morphology for filament identification, presenting a complementary approach to current algorithms which use matched filtering or critical manifolds. Unlike other methods, FILFINDER identifies filaments over a wide dynamic ran…
Discovery of a 3.5 keV line in the Galactic Centre and a critical look at the origin of the line across astronomical targets
Profumo, Stefano; Jeltema, Tesla
We examine the claimed excess X-ray line emission near 3.5 keV including both a new analysis of XMM-Newton observations of the Milky Way centre and a reanalysis of the data on M 31 and clusters. In no case do we find conclusive evidence for an excess. In the case of the Galactic Centre, we show that known plasma lines, including in particular K XV…
A spectral-timing model for ULXs in the supercritical regime
Pintore, Fabio; Middleton, Matthew J.; Roberts, Timothy P. +2 more
Ultraluminous X-ray sources (ULXs) with luminosities lying between ∼3 × 1039 and 2 × 1040 erg s-1 represent a contentious sample of objects as their brightness, together with a lack of unambiguous mass estimates for the vast majority of the central objects, leads to a degenerate scenario where the accretor could be…
HST hot-Jupiter transmission spectral survey: detection of potassium in WASP-31b along with a cloud deck and Rayleigh scattering
Aigrain, S.; Pont, F.; Fortney, J. J. +15 more
We present Hubble Space Telescope optical and near-IR transmission spectra of the transiting hot-Jupiter WASP-31b. The spectrum covers 0.3-1.7 µm at a resolution R ∼ 70, which we combine with Spitzer photometry to cover the full-optical to IR. The spectrum is dominated by a cloud deck with a flat transmission spectrum which is apparent at wa…