Search Publications
Radio, X-ray, and γ-ray emission models of the colliding-wind binary WR140
Pittard, J. M.; Dougherty, S. M.
We use hydrodynamical models of the wind-collision region in the archetype colliding-wind system WR140 to determine the spatial and spectral distributions of the radio, X-ray, and γ-ray emission from shock-accelerated electrons. Our calculations are for orbital phase 0.837 when the observed radio emission is close to maximum. Using the observed th…
An XMM-Newton view of the young open cluster NGC 6231 - II. The OB star population
Gosset, E.; Nazé, Y.; Rauw, G. +2 more
In this second paper of the series, we pursue the analysis of the 180-ks XMM-Newton campaign towards the young open cluster NGC 6231 and we focus on its rich OB star population. We present a literature-based census of the OB stars in the field of view with more than one hundred objects, among which 30 per cent can be associated with an X-ray sourc…
XMM-Newton study of the complex and variable spectrum of NGC 4051
Maraschi, L.; Cappi, M.; Ponti, G. +3 more
We study the X-ray spectral variability of the narrow line Seyfert 1 galaxy NGC 4051 as observed during two XMM-Newton observations. To gain insight on the general behaviour, we first apply model-independent techniques such as rms spectra and flux-flux plots. We then perform time-resolved spectral analysis by splitting the observations into 68 spe…
Parametric strong gravitational lensing analysis of Abell 1689
Pannella, M.; Seitz, S.; Halkola, A.
We have derived the mass distribution of galaxy cluster Abell 1689 within 0.3h-170Mpc of the cluster centre using its strong lensing (SL) effect on 32 background galaxies, which are mapped in altogether 107 multiple images. The multiple images are based on some from the literature with modifications to both include new and ex…
Investigating the nature of narrow-line Seyfert 1 galaxies with high-energy spectral complexity
Gallo, L. C.
With the commissioning of XMM-Newton came the discovery of 2.5-10keV spectral complexity in some narrow-line Seyfert 1 galaxies (NLS1). This high-energy complexity can be manifested as sharp, spectral drops or gradual curvature in the spectrum. Models which are normally considered are ionized reflection and partial covering. In this work, we defin…
A maximum-likelihood method for fitting colour-magnitude diagrams
Naylor, Tim; Jeffries, R. D.
We present a maximum-likelihood method for fitting two-dimensional model distributions to stellar data in colour-magnitude space. This allows one to include (for example) binary stars in an isochronal population. The method also allows one to derive formal uncertainties for fitted parameters, and assess the likelihood that a good fit has been foun…
HST/STIS optical spectroscopy of five super star clusters in the starburst galaxy M82
O'Connell, R. W.; Gallagher, J. S.; Smith, L. J. +3 more
We present optical spectroscopy obtained with the Space Telescope Imaging Spectrograph of five young massive star clusters in the starburst galaxy M82. A detailed analysis is performed for one cluster `M82-A1' and its immediate environment in the starburst core. From Hubble Space Telescope archive images, we find that it is elliptical with an effe…
Updating reionization scenarios after recent data
Ferrara, A.; Choudhury, T. Roy
The recent release of data on (i) high-redshift source counts from the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) Hubble Ultra Deep Field (HUDF) and (ii) electron scattering optical depth from the Wilkinson Microwave Anisotropy Probe (WMAP) requires a re-examination of reionization scenarios. Using an improved self-consistent reio…
The XMM Large-Scale Structure survey: the X-ray pipeline and survey selection function
Chiappetti, L.; Altieri, B.; Valtchanov, I. +11 more
We present the X-ray pipeline developed for the purpose of the cluster search in the XMM Large-Scale Structure (XMM-LSS) survey. It is based on a two-stage procedure via a dedicated handling of the Poisson nature of the signal: (i) source detection on multiresolution wavelet filtered images and (ii) source analysis by means of a maximum likelihood…
On the origin and excitation of the extended nebula surrounding NGC1275
Fabian, A. C.; Johnstone, R. M.; Crawford, C. S. +1 more
We use line-of-sight velocity information on the filamentary emission-line nebula of NGC1275 to infer a dynamical model of the nebula's flow through the surrounding intracluster gas. We detect outflowing gas and flow patterns that match simulations of buoyantly rising bubbles from which we deduce that some of the nebula filaments have been drawn o…