Search Publications
The Sloan Digital Sky Survey Quasar Catalog: Twelfth data release
Nandra, Kirpal; Pâris, Isabelle; Petitjean, Patrick +43 more
We present the Data Release 12 Quasar catalog (DR12Q) from the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey III. This catalog includes all SDSS-III/BOSS objects that were spectroscopically targeted as quasar candidates during the full survey and that are confirmed as quasars via visual inspection of the spectra, h…
On the use of C-stat in testing models for X-ray spectra
Kaastra, J. S.
Context. It has been shown that for the analysis of X-ray spectra the C-statistic, contrary to the χ2-statistic, provides unbiased estimates of the model parameters and their uncertainty ranges.
Aims: However, it is often stated that the C-statistic cannot be used to carry out statistical tests on the goodness of fit of the model, …
Quasars as standard candles. I. The physical relation between disc and coronal emission
Lusso, E.; Risaliti, G.
Context. A tight non-linear relation exists between the X-ray and UV emission in quasars (I.e. LX ∝LUVγ), with a dispersion of 0.2 dex over approximately three orders of magnitude in luminosity. Such observational evidence has two relevant consequences: (1) an ubiquitous physical mechanism must regulate the energy transfer fr…
Radial metal abundance profiles in the intra-cluster medium of cool-core galaxy clusters, groups, and ellipticals
Zhang, Y. -Y.; Simionescu, A.; Kaastra, J. S. +10 more
The hot intra-cluster medium (ICM) permeating galaxy clusters and groups is not pristine, as it has been continuously enriched by metals synthesised in Type Ia (SNIa) and core-collapse (SNcc) supernovae since the major epoch of star formation (z ≃ 2-3). The cluster/group enrichment history and mechanisms responsible for releasing and mixing the me…
ULX spectra revisited: Accreting, highly magnetized neutron stars as the engines of ultraluminous X-ray sources
Vasilopoulos, Georgios; Bachetti, Matteo; Godet, Olivier +3 more
Aims: In light of recent discoveries of pulsating ultraluminous X-ray sources (ULXs) and recently introduced theoretical schemes that propose neutron stars (NSs) as the central engines of ULXs, we revisit the spectra of eighteen well known ULXs, in search of indications that favour this newly emerging hypothesis.
Methods: We examine the …
The X-ray properties of z 6 luminous quasars
Brandt, W. N.; Moretti, A.; Vignali, C. +2 more
We present a systematic analysis of X-ray archival data of all the 29 quasars (QSOs) at z> 5.5 observed so far with Chandra, XMM-Newton and Swift-XRT, including the most-distant quasar ever discovered, ULAS J1120+0641 (z = 7.08). This study allows us to place constraints on the mean spectral properties of the primordial population of luminous T…
The WISSH quasars project. III. X-ray properties of hyper-luminous quasars
Fiore, F.; Bianchi, S.; Martocchia, S. +14 more
We performed a survey of the X-ray properties of 41 objects from the WISE/SDSS selected hyper-luminous (WISSH) quasars sample, which includes 86 broad-line quasars with bolometric luminosity LBol ≳ 2 × 1047 erg s-1 shining at z 2-4. We used both proprietary and archival Chandra and XMM-Newton observations. Twenty-o…
Chasing obscuration in type-I AGN: discovery of an eclipsing clumpy wind at the outer broad-line region of NGC 3783
Kaastra, J. S.; Kriss, G. A.; Arav, N. +21 more
In 2016 we carried out a Swift monitoring programme to track the X-ray hardness variability of eight type-I AGN over a year. The purpose of this monitoring was to find intense obscuration events in AGN, and thereby study them by triggering joint XMM-Newton, NuSTAR, and HST observations. We successfully accomplished this for NGC 3783 in December 20…
Mapping the kinetic Sunyaev-Zel'dovich effect toward MACS J0717.5+3745 with NIKA
Adam, R.; Arnaud, M.; Benoît, A. +47 more
Measurement of the gas velocity distribution in galaxy clusters provides insight into the physics of mergers, through which large scale structures form in the Universe. Velocity estimates within the intracluster medium (ICM) can be obtained via the Sunyaev-Zel'dovich (SZ) effect, but its observation is challenging both in term of sensitivity requi…
An X-ray/SDSS sample. I. Multi-phase outflow incidence and dependence on AGN luminosity
Brusa, M.; Lanzuisi, G.; Perna, M. +2 more
Aims: The connection between the growth of super-massive black holes (SMBHs) and the evolution of their host galaxies is nowadays well established, although the underlying mechanisms explaining their mutual relations are still debated. Multi-phase fast, massive outflows have been postulated to play a crucial role in this process. The aim of t…