Search Publications
The structures of distant galaxies - III. The merger history of over 20000 massive galaxies at z < 1.2
Conselice, Christopher J.; Bluck, Asa F. L.; Yang, Cui
Utilizing deep Hubble Space Telescope imaging from the two largest field galaxy surveys, the Extended Groth Strip and the Cosmic Evolution Survey (COSMOS), we examine the structural properties, and derive the merger history for 21902 galaxies with M* > 1010Msolar at z < 1.2. We examine the structural concentr…
The evolution of the high-energy cut-off in the X-ray spectrum of GX 339-4 across a hard-to-soft transition
Belloni, T.; Homan, J.; Motta, S.
We report on X-ray observations of the black hole candidate GX 339-4 during its 2006/2007 outburst. The hardness-intensity diagram (HID) of all RXTE/Proportional Counter Array data combined shows a q-shaped track similar to that observed in previous outbursts. The evolution through the HID suggests that in the early phase of the outburst the sourc…
HiZELS: a high-redshift survey of Hα emitters - II. The nature of star-forming galaxies at z = 0.84
Ivison, R. J.; Smail, Ian; Cirasuolo, M. +7 more
New results from a large survey of Hα emission-line galaxies at z = 0.84 using the Wide Field Camera on the United Kingdom Infrared Telescope and a custom narrow-band filter in the J band are presented as part of the High-z Emission Line Survey (HiZELS). The deep narrow-band images reach an effective flux limit of FHα ~ 10-16…
Accretion disc variability in the hard state of black hole X-ray binaries
Wilkinson, Tony; Uttley, Philip
XMM-Newton X-ray spectra of the hard state black hole X-ray binaries (BHXRBs) SWIFTJ1753.5-0127 and GX339-4 show evidence for accretion disc blackbody emission, in addition to hard power laws. The soft and hard band power spectral densities (PSDs) of these sources demonstrate variability over a wide range of time-scales. However, on time-scales of…
The XMM-Newton long look of NGC 1365: uncovering of the obscured X-ray source
Zezas, A.; Bianchi, S.; Guainazzi, M. +10 more
We present an analysis of the extreme obscuration variability observed during an XMM-Newton 5-d continuous monitoring of the active galactic nuclei (AGN) in NGC 1365. The source was in a reflection-dominated state in the first ~1.5 d, then a strong increase in the 7-10 keV emission was observed in ~10 h, followed by a symmetric decrease. The spect…
The Hubble flow around the Local Group
Karachentsev, I. D.; Kashibadze, O. G.; Tully, R. B. +1 more
We use updated data on distances and velocities of galaxies in the proximity of the Local Group (LG) in order to establish properties of the local Hubble flow. For 30 neighbouring galaxies with distances 0.7 < DLG < 3.0 Mpc, the local flow is characterized by the Hubble parameter Hloc = (78 +/- 2)kms-1 Mpc
Spectral variability of ultraluminous X-ray sources
Poutanen, Juri; Kajava, Jari J. E.
We study spectral variability of 11 ultraluminous X-ray sources (ULX) using archived XMM-Newton and Chandra observations. We use three models to describe the observed spectra: a power law, a multicolour disc (MCD) and a combination of these two models. We find that seven ULXs show a correlation between the luminosity LX and the photon i…
Optical-to-X-ray emission in low-absorption AGN: results from the Swift-BAT 9-month catalogue
Fabian, A. C.; Mushotzky, R. F.; Winter, L. M. +1 more
We present simultaneous optical-to-X-ray spectral energy distributions (SEDs) from Swift's X-ray and UV-optical telescopes (XRTs and UVOTs) for a well-selected sample of 26 low-redshift (z < 0.1) active galactic nuclei (AGN) from the Swift/Burst Alert Telescope 9-month catalogue, the largest well-studied, hard X-ray-selected survey of local AGN…
3D modelling of the colliding winds in η Carinae - evidence for radiative inhibition
Corcoran, M. F.; Hamaguchi, K.; Pittard, J. M. +2 more
The X-ray emission from the supermassive star ηCar is simulated using a 3D model of the wind-wind collision. In the model the intrinsic X-ray emission is spatially extended and energy dependent. Absorption due to the unshocked stellar winds and the cooled post-shock material from the primary LBV star is calculated as the intrinsic emission is ray …
Globular cluster systems in nearby dwarf galaxies - II. Nuclear star clusters and their relation to massive Galactic globular clusters
Georgiev, Iskren Y.; Goudfrooij, Paul; Puzia, Thomas H. +2 more
We compare nuclear globular clusters (nGCs) in dwarf galaxies and Galactic GCs with extended (hot) horizontal branches (EHB-GCs) in order to test the suggested external origin of the latter and the conditions at which GC self-enrichment can operate. Using luminosities and structural parameters of nGCs in low-mass (mainly late-type) dwarf galaxies …