Search Publications
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…
20-100 keV properties of cataclysmic variables detected in the INTEGRAL/IBIS survey
Hill, A. B.; Knigge, C.; Bird, A. J. +5 more
Analysis of INTEGRAL/IBIS survey observations has revealed that the rare intermediate polar and asynchronous polar cataclysmic variables (CVs) are consistently found to emit in the 20-100 keV energy band, whereas synchronous polars and the common non-magnetic CVs rarely do so. From the correlation of a candidate INTEGRAL/IBIS survey source list wi…
Cooling of the quasi-persistent neutron star X-ray transients KS 1731-260 and MXB 1659-29
Homan, Jeroen; Miller, Jon M.; Cackett, Edward M. +3 more
We present Chandra and XMM-Newton X-ray observations that monitor the neutron star cooling of the quasi-persistent neutron star X-ray transients KS 1731-260 and MXB 1659-29 for approximately 4 yr after these sources returned to quiescence from prolonged outbursts. In both sources the outbursts were long enough to significantly heat the neutron sta…
The interplay between star formation and the nuclear environment of our Galaxy: deep X-ray observations of the Galactic centre Arches and Quintuplet clusters
Wang, Q. Daniel; Dong, Hui; Lang, Cornelia
The Galactic centre (GC) provides a unique laboratory for a detailed examination of the interplay between massive star formation and the nuclear environment of our Galaxy. Here, we present a 100-ks Chandra Advanced CCD Imaging Spectrometer (ACIS) observation of the Arches and Quintuplet star clusters. We also report on a complementary mapping of t…