Results for "R. Bird"

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Two definable subcategories of maximal Cohen-Macaulay modulesApr 18 2019Over a Cohen-Macaulay ring we consider two extensions of the maximal Cohen-Macaulay modules from the viewpoint of definable subcategories, which are closed under direct limits, direct products and pure submodules. After describing these categories, we ... More
Giant Lyman-Alpha Nebulae in the Illustris SimulationMay 11 2016Dec 19 2016Several `giant' Lyman-$\alpha$ (Ly$\alpha$) nebulae with extent $\gtrsim 300\,$kpc and observed Ly$\alpha$ luminosity of $\gtrsim 10^{44}\,{\rm erg}\,{\rm s}^{-1}\,{\rm cm}^{-2}\,{\rm arcsec}^{-2}$ have recently been detected, and it has been speculated ... More
SWIFT/XRT follow-up observations of INTEGRAL AGNsOct 12 2006In five years of operation, data from INTEGRAL has been used to discover a large number of gamma-ray sources, a substantial fraction of which have turned out to be active galactic nuclei (AGN). Recently Bassani et al. (2006) have presented a sample of ... More
An efficient implementation of massive neutrinos in non-linear structure formation simulationsSep 03 2012Nov 19 2012Massive neutrinos make up a fraction of the dark matter, but due to their large thermal velocities, cluster significantly less than cold dark matter (CDM) on small scales. An accurate theoretical modelling of their effect during the non-linear regime ... More
Dark matter pair-production in b -> s transitionsJan 12 2006Mar 05 2006The flavour-changing neutral current transition b \to s can serve as a sensitive probe of WIMP dark matter models, if the WIMP mass is under 2 GeV. In this work we extend our earlier analysis to a generic class of models where the interaction between ... More
A spin-polarised first principles study of short dangling bond wires on Si(001)Jan 30 2003Mar 06 2003Short dangling bond wires (DB wires), fabricated on H-terminated Si(001) surfaces, show patterns of displacement that depend on their length. We have performed density function calculations, with and without spin-polarisation, designed to investigate ... More
Integral/Ibis Census of the Sky Beyond 100 kevAug 08 2006We report on the first census of INTEGRAL/IBIS detections ($\gtrsim 4\sigma$ significance) above 100 keV based on the Core Program and public Open time observations up to April 2005. There are 49 sources detected in the 100-150 keV band of which 14 are ... More
The AGN nature of three INTEGRAL sources: IGR J18249-3243, IGR J19443+2117 and IGR J22292+6647Nov 14 2008The third INTEGRAL/IBIS survey has revealed several new hard X-ray sources, which are still unclassified. To identify these sources, we need to find their counterparts at other wavelengths and then study their nature. The capability of XRT on board Swift ... More
Swift/XRT follow-up observations of TeV sources of the HESS Inner Galaxy surveyJul 15 2006In order to provide a firm identification of the newly discovered Galactic TeV sources, a search for counterparts in a broad band from soft X-ray to soft gamma-rays is crucial as data in these wavebands allow us to distinguish between different types ... More
Unveiling the nature of INTEGRAL objects through optical spectroscopy. V. Identification and properties of 21 southern hard X-ray sourcesAug 18 2006Optical spectroscopic identification of the nature of 21 unidentified southern hard X-ray objects is reported here in the framework of our campaign aimed at determining the nature of newly-discovered and/or unidentified sources detected by INTEGRAL. Our ... More
INTEGRAL IGR J18135-1751=HESS J1813-178: A new cosmic high energy accelerator from keV to TeVMay 10 2005Jul 14 2005We report the discovery of a soft gamma ray source, namely IGR J18135-1751, detected with the IBIS imager on board the INTEGRAL satellite. The source is persistent and has a 20-100 keV luminosity of $\sim$5.7 $\times$ 10$^{34}$ erg s$^{-1}$ (assuming ... More
The Open Language Archives Community and Asian Language ResourcesOct 03 2001The Open Language Archives Community (OLAC) is a new project to build a worldwide system of federated language archives based on the Open Archives Initiative and the Dublin Core Metadata Initiative. This paper aims to disseminate the OLAC vision to the ... More
The Giesy--James theorem for general index $p$, with an application to operator ideals on the $p$th James spaceSep 08 2011A theorem of Giesy and James states that $c_0$ is finitely representable in James' quasi-reflexive Banach space $J_2$. We extend this theorem to the $p$th quasi-reflexive James space $J_p$ for each $p \in (1,\infty)$. As an application, we obtain a new ... More
Practical Lossless Compression with Latent Variables using Bits Back CodingJan 15 2019Deep latent variable models have seen recent success in many data domains. Lossless compression is an application of these models which, despite having the potential to be highly useful, has yet to be implemented in a practical manner. We present `Bits ... More
Cross-correlation between thermal Sunyaev-Zeldovich effect and the integrated Sachs-Wolfe effectJun 02 2016Sep 19 2016Large-angle fluctuations in the cosmic microwave background temperature induced by the integrated Sachs-Wolfe effect and Compton-y distortions from the thermal Sunyaev-Zeldovich (tSZ) effect are both due to line-of-sight density perturbations. Here we ... More
Electronic damping of molecular motion at metal surfacesSep 30 2009A method for the calculation of the damping rate due to electron-hole pair excitation for atomic and molecular motion at metal surfaces is presented. The theoretical basis is provided by Time Dependent Density Functional Theory (TDDFT) in the quasi-static ... More
The Lifetime of FRIIs in Groups and Clusters: Implications for Radio-Mode FeedbackSep 13 2007Dec 09 2007We determine the maximum lifetime t_max of 52 FRII radio sources found in 26 central group galaxies from cross correlation of the Berlind SDSS group catalog with the VLA FIRST survey. Mock catalogs of FRII sources were produced to match the selection ... More
Electron-hole pair creation by atoms incident on a metal surfaceSep 30 2009Electron-hole pair creation by an adsorbate incident on a metal surface is described using \textit{ab initio} methods. The approach starts with standard first principles electronic structure theory, and proceeds to combine classical, quantum oscillator ... More
Simulating the Carbon Footprint of Galactic HalosDec 07 2015Jul 27 2016We compare simulations, including the Illustris simulations, to observations of CIV and CII absorption at z=2-4. These are the CIV column density distribution function in the column density range $10^{12} - 10^{15}$ cm$^{-2}$, the CIV equivalent width ... More
Soliton effects in dangling-bond wires on Si(001)Jan 30 2003Dangling bond wires on Si(001) are prototypical one dimensional wires, which are expected to show polaronic and solitonic effects. We present electronic structure calculations, using the tight binding model, of solitons in dangling-bond wires, and demonstrate ... More
Galactic Positrons as a Probe of Large Extra DimensionsDec 24 2008Dec 24 2008In the last decade, there has been increased interest in the possibility that the Universe contains large additional dimensions. In this article it is proposed that the Kaluza-Klein modes which are predicted to exist in such models will be trapped in ... More
The Minimal Model of Radion Mediated Dark MatterDec 24 2008Based on the results from numerous astrophysics experiments, it is currently believed that the majority of matter in the Universe is in some unknown form, known as dark matter. In the past it has been common to model dark matter as a massive particle ... More
Computational PhonologyApr 10 2002Phonology, as it is practiced, is deeply computational. Phonological analysis is data-intensive and the resulting models are nothing other than specialized data structures and algorithms. In the past, phonological computation - managing data and developing ... More
The upgrade of the LHCb Vertex LocatorOct 03 2014Nov 10 2014The LHCb experiment is set for a significant upgrade, which will be ready for Run 3 of the LHC in 2020. This upgrade will allow LHCb to run at a significantly higher instantaneous luminosity and collect an integrated luminosity of $50\,\text{fb}^{-1}$ ... More
In silico investigation of lactone and thiolactone inhibitors in bacterial quorum sensing using molecular modelingMay 16 2013In the present study, the origin of the anti-quorum sensing (QS) activities of several members of a recently synthesized and in vitro tested class of lactone and thiolactone based inhibitors were computationally investigated. Docking and molecular dynamic ... More
The Early Universe as a Probe of New PhysicsDec 24 2008The Standard Model of Particle Physics has been verified to unprecedented precision in the last few decades. However there are still phenomena in nature which cannot be explained, and as such new theories will be required. Since terrestrial experiments ... More
A lexical database tool for quantitative phonological researchJul 22 1997A lexical database tool tailored for phonological research is described. Database fields include transcriptions, glosses and hyperlinks to speech files. Database queries are expressed using HTML forms, and these permit regular expression search on any ... More
Minimally Parametric Constraints on the Primordial Power Spectrum from Lyman-alphaMay 21 2010Current analyses of the Lyman-alpha forest assume that the primordial power spectrum of density perturbations obeys a simple power law, a strong theoretical assumption which should be tested. Employing a large suite of numerical simulations which drop ... More
Automated tone transcriptionOct 24 1994Oct 25 1994In this paper I report on an investigation into the problem of assigning tones to pitch contours. The proposed model is intended to serve as a tool for phonologists working on instrumentally obtained pitch data from tone languages. Motivation and exemplification ... More
An Efficient and Accurate Hybrid Method for Simulating Non-Linear Neutrino StructureMar 27 2018Sep 02 2018We present an efficient and accurate method for simulating massive neutrinos in cosmological structure formation simulations, together with an easy to use public implementation. Our method builds on our earlier implementation of the linear response approximation ... More
Non-Ergodicity & Microscopic Symmetry Breaking of the Conductance Fluctuations in Disordered Mesoscopic GrapheneMar 28 2012Oct 18 2012We show a dramatic deviation from ergodicity for the conductance fluctuations in graphene. In marked contrast to the ergodicity of dirty metals, fluctuations generated by varying magnetic field are shown to be much smaller than those obtained when sweeping ... More
PhonologyApr 11 2002Phonology is the systematic study of the sounds used in language, their internal structure, and their composition into syllables, words and phrases. Computational phonology is the application of formal and computational techniques to the representation ... More
The implications of an extended dark energy cosmology with massive neutrinos for cosmological tensionsMar 06 2018Sep 02 2018We perform a comprehensive analysis of the most common early- and late-Universe solutions to the $H_0$, Ly-$\alpha$, and $S_8$ discrepancies. When considered on their own, massive neutrinos provide a natural solution to the $S_8$ discrepancy at the expense ... More
The counterpart/s of IGR J20159+3713/SWIFT J2015.9+3715: dissecting a complex region with emission from keV to TeVOct 29 2013We report on the identification of a new soft gamma-ray source, namely IGR J20159+3713/SWIFT J2015.9+3715, first detected by INTEGRAL/IBIS and then confirmed by Swift/BAT. The source, which has an observed 20-100 keV flux in the range (0.7-1.4) x 10^(-11) ... More
Systematic effects induced on IBIS detectors by background and inhomogeneity of the spatial responseSep 15 2003The spatial distribution of the background events may affect the source detection capability of IBIS at high energies (> 200 keV) for both ISGRI and PICsIT layers. The observed background is found to be variable and spatially structured, and in some cases ... More
IGR J17354-3255 as a candidate intermediate SFXT possibly associated with the transient MeV AGL J1734-3310Jun 21 2011We present spectral and temporal results from INTEGRAL long-term monitoring of the unidentified X-ray source IGR J17354-3255. We show that it is a weak persistent hard X-ray source spending a major fraction of the time in an out-of-outburst state with ... More
Identification of newly-discovered sources belonging to the 4th IBIS catalog and to the 54 months Palermo Swift/BAT catalogFeb 25 2013The most recent all-sky surveys performed with the INTEGRAL and SWIFT satellites allowed the detection of more than 1500 sources in hard X-rays above 20 keV. About one quarter of them has no obvious counterpart at other wavelengths and therefore could ... More
The INTEGRAL/IBIS AGN catalogue: an updateApr 21 2016Apr 27 2016In the most recent IBIS survey based on observations performed during the first 1000 orbits of INTEGRAL, are listed 363 high energy emitters firmly associated with AGN, 107 of which are reported here for the first time. We have used X-ray data to image ... More
Chasing extreme blazars with INTEGRALFeb 11 2013Within the blazar population, hard X-ray selected objects are of particular interest as they tend to lie at each end of the blazar sequence. In particular, flat spectrum radio quasars located at high redshifts display the most powerful jets, the largest ... More
INTEGRAL view of the Extragalactic SkyDec 21 2011Presented in this work is the most comprehensive INTEGRAL AGN sample: it includes 272 active galaxies for which optical identifications and redshifts are available. 2-10 keV fluxes and column density measurements are also collected for all the sample ... More
Energy loss of atoms at metal surfaces due to electron-hole pair excitations: First-principles theory of "chemicurrents"Sep 30 2009A method is presented for calculating electron-hole pair excitation due to an incident atom or molecule interacting with a metal surface. Energy loss is described using an \textit{ab initio} approach that obtains a position-dependent friction coefficient ... More
Swift/XRT observations of newly discovered INTEGRAL sourcesApr 16 2013With respect to the recent INTEGRAL/IBIS 9-year Galactic Hard X-ray Survey (Krivonos et al. 2012), we use archival Swift/XRT observations in conjunction with multi-wavelength information to discuss the counterparts of a sample of newly discovered objects. ... More
HESS J1616-508: likely powered by PSR J1617-5055Jul 05 2007HESS J1616-508 is one of the brightest emitters in the TeV sky. Recent observations with the IBIS/ISGRI telescope on board the INTEGRAL spacecraft have revealed that a young, nearby and energetic pulsar, PSR J1617-5055, is a powerful emitter of soft gamma-rays ... More
Voltage-induced suppression of weak localization in grapheneFeb 22 2017Feb 28 2018In this theoretical study, we explore the manner in which the quantum correction due to weak localization is suppressed in weakly-disordered graphene, when it is subjected to the application of a non-zero voltage. Using a nonequilibrium Green function ... More
Swift/XRT follow-up observations of unidentified INTEGRAL/IBIS sourcesMar 05 2010Many sources listed in the 4th IBIS/ISGRI survey are still unidentified, i.e. lacking an X-ray counterpart or simply not studied at lower energies (< 10 keV). The cross-correlation between the list of IBIS sources in the 4th catalogue and the Swift/XRT ... More
A macroscopic scale model of bacterial flagellar bundlingDec 21 2003Escherichia coli and other bacteria use rotating helical filaments to swim. Each cell typically has about four filaments, which bundle or disperse depending on the sense of motor rotation. To study the bundling process, we built a macroscopic scale model ... More
X-ray, optical and infrared investigation of the candidate Supergiant Fast X-ray Transient IGR J18462-0223May 07 2013We report on a broad-band X-ray study (0.5-60 keV) of the poorly known candidate Supergiant Fast X-ray Transient (SFXT) IGR J18462-0223, and on optical and near-infrared (NIR) followup observations of field objects. The out-of-outburst X-ray state has ... More
Five new INTEGRAL unidentified hard X-Ray sources uncovered by ChandraJun 23 2010The IBIS imager on board INTEGRAL, with a sensitivity better than a mCrab in deep observations and a point source location accuracy of the order of few arcminutes, has localized so far 723 hard X-ray sources in the 17--100 keV energy band, of which a ... More
Periodic Variability During the X-ray Decline of 4U 1636-53May 10 2005We report the onset of a large amplitude, statistically significant periodicity (~46 d) in the RXTE/ASM data of the prototype X-ray burster 4U 1636-53, the X-ray flux of which has been gradually declining over the last four years. This behaviour is remarkably ... More
Swift/XRT observations of unidentified INTEGRAL/IBIS sourcesDec 08 2009Dec 10 2009The 4th IBIS/ISGRI survey lists 723 hard X-ray sources many still unidentified. We cross-correlated the list of the sources included in the 4th IBIS catalogue with the Swift/XRT data archive, finding a sample of 20 objects for which XRT data could help ... More
INTEGRAL and Swift/XRT observations of the SFXT IGR J16479-4514: from quiescence to fast flaring activityMay 05 2008Context: IGR J16479-4514 is a fast X-ray transient known to display flares lasting typically a few hours. Recently, its counterpart has been identified with a supergiant star, therefore the source can be classified as member of the newly discovered class ... More
Broadband study of hard X-ray selected absorbed AGNNov 08 2011[Abridged]We report on the broadband X-ray properties of a complete sample of absorbed Seyfert galaxies hard X-ray selected with INTEGRAL. The sample is composed of 33 sources: 15 are newly discovered above 20 keV while 18 are already known AGN. For 17 ... More
The peculiar high-mass X-ray binary 1ES 1210-646Jan 04 2010Using data collected with the BeppoSAX, INTEGRAL and Swift satellites, we report and discuss the results of a study on the X-ray emission properties of the X-ray source 1ES 1210-646, recently classified as a high-mass X-ray binary through optical spectroscopy. ... More
INTEGRAL/IBIS and Swift/XRT observations of hard cataclysmic variablesOct 10 2008The analysis of the third INTEGRAL/IBIS survey has revealed several new cataclysmic variables, most of which turned out to be intermediate polars, thus confirming that these objects are strong emitters in hard X-rays. Here we present high energy spectra ... More
IGR J12319-0749: evidence for another extreme blazar found with INTEGRALMay 14 2012We report on the identification of a new soft gamma-ray source, IGR J12319-0749, detected with the IBIS imager on board the INTEGRAL satellite. The source, which has an observed 20-100 keV flux of ~8.3 x 10^{-12} erg cm^{-2} s^{-1}, is spatially coincident ... More
A Mass Model for Estimating the Gamma Ray Background of the Burst and Transient Source ExperimentNov 19 2002Orbiting x-ray and gamma ray instruments are subject to large background count rates due to local particle fluxes in the space environment. The ability of an instrument to make calibrated measurements of the flux from a source of interest is highly dependent ... More
Contrasting behaviour from two Be/X-ray binary pulsars: insights into differing neutron star accretion modesApr 29 2013In this paper we present the identification of two periodic X-ray signals coming from the direction of the Small Magellanic Cloud (SMC). On detection with the Rossi X-ray Timing Explorer (RXTE), the 175.4s and 85.4s pulsations were considered to originate ... More
The Magellanic Bridge: evidence for a population of X-ray binariesDec 15 2009INTEGRAL observations of the Small Magellanic Cloud region have resulted in the serendipitous detection of two transient hard X-ray sources in the Magellanic Bridge. In this paper we present the timing and spectral characteristics of these sources across ... More
Broadband X-ray properties of absorbed AGNDec 20 2011In this paper we report on the broadband X-ray properties of a complete sample of 33 absorbed Seyfert galaxies hard X-ray selected with integral. The high quality broadband spectra obtained with both xmm, and integral-IBIS data are well reproduced with ... More
The power spectrum of the Milky Way: Velocity fluctuations in the Galactic diskOct 29 2014Feb 16 2015We investigate the kinematics of stars in the mid-plane of the Milky Way on scales between 25 pc and 10 kpc with data from the Apache Point Observatory Galactic Evolution Experiment (APOGEE), the Radial Velocity Experiment (RAVE), and the Geneva-Copenhagen ... More
Review on Active Galactic Nuclei at hard X-ray energiesFeb 11 2013Hard X-ray surveys are an important tool for the study of active galactic nuclei (AGN): they provide almost an unbiased view of absorption in the extragalactic population, allow the study of spectral features such as reflection and high energy cut-off ... More
A Grid Based Architecture for High-Performance NLPAug 05 2003We describe the design and early implementation of an extensible, component-based software architecture for natural language engineering applications which interfaces with high performance distributed computing services. The architecture leverages existing ... More
The Open Language Archives Community: An infrastructure for distributed archiving of language resourcesJun 10 2003New ways of documenting and describing language via electronic media coupled with new ways of distributing the results via the World-Wide Web offer a degree of access to language resources that is unparalleled in history. At the same time, the proliferation ... More
Grid-Enabling Natural Language Engineering By StealthApr 22 2003We describe a proposal for an extensible, component-based software architecture for natural language engineering applications. Our model leverages existing linguistic resource description and discovery mechanisms based on extended Dublin Core metadata. ... More
A Formal Framework for Linguistic Annotation (revised version)Oct 26 2000`Linguistic annotation' covers any descriptive or analytic notations applied to raw language data. The basic data may be in the form of time functions - audio, video and/or physiological recordings - or it may be textual. The added notations may include ... More
Extending Dublin Core Metadata to Support the Description and Discovery of Language ResourcesAug 14 2003As language data and associated technologies proliferate and as the language resources community expands, it is becoming increasingly difficult to locate and reuse existing resources. Are there any lexical resources for such-and-such a language? What ... More
A Formal Framework for Linguistic AnnotationMar 02 1999`Linguistic annotation' covers any descriptive or analytic notations applied to raw language data. The basic data may be in the form of time functions -- audio, video and/or physiological recordings -- or it may be textual. The added notations may include ... More
Annotation Graphs and Servers and Multi-Modal Resources: Infrastructure for Interdisciplinary Education, Research and DevelopmentApr 10 2002Annotation graphs and annotation servers offer infrastructure to support the analysis of human language resources in the form of time-series data such as text, audio and video. This paper outlines areas of common need among empirical linguists and computational ... More
Giant Lyman-Alpha Nebulae in the Illustris SimulationMay 11 2016Several `giant' Lyman-$\alpha$ (Ly$\alpha$) nebulae with extent $\gtrsim 300\,$kpc and observed Ly$\alpha$ luminosity of $\gtrsim 10^{44}\,{\rm erg}\,{\rm s}^{-1}\,{\rm cm}^{-2}\,{\rm arcsec}^{-2}$ have recently been detected, and it has been speculated ... More
Building an Open Language Archives Community on the OAI FoundationFeb 14 2003The Open Language Archives Community (OLAC) is an international partnership of institutions and individuals who are creating a worldwide virtual library of language resources. The Dublin Core (DC) Element Set and the OAI Protocol have provided a solid ... More
Querying Databases of Annotated SpeechApr 11 2002Annotated speech corpora are databases consisting of signal data along with time-aligned symbolic `transcriptions'. Such databases are typically multidimensional, heterogeneous and dynamic. These properties present a number of tough challenges for representation ... More
Substructure in Clusters and Central Galaxy Peculiar VelocitiesFeb 23 1994Formation theories for central dominant galaxies in clusters require them to be located at the minimum of the cluster gravitational potential. However, 32\% (8 out of 25) of the clusters with more than 50 measured redshifts have central galaxies with ... More
Reproducing the Kinematics of Damped Lyman-alpha SystemsJul 29 2014Jan 07 2015We examine the kinematic structure of Damped Lyman-alpha Systems (DLAs) in a series of cosmological hydrodynamic simulations using the AREPO code. We are able to match the distribution of velocity widths of associated low ionisation metal absorbers substantially ... More
The OLAC Metadata Set and Controlled VocabulariesMay 21 2001As language data and associated technologies proliferate and as the language resources community rapidly expands, it has become difficult to locate and reuse existing resources. Are there any lexical resources for such-and-such a language? What tool can ... More
The BlueTides Simulation: First Galaxies and ReionizationApr 24 2015We introduce the BlueTides simulation and report initial results for the luminosity functions of the first galaxies and AGN, and their contribution to reionization. BlueTides was run on the BlueWaters cluster at NCSA from $z=99$ to $z=8.0$ and includes ... More
Seven Dimensions of Portability for Language Documentation and DescriptionApr 10 2002The process of documenting and describing the world's languages is undergoing radical transformation with the rapid uptake of new digital technologies for capture, storage, annotation and dissemination. However, uncritical adoption of new tools and technologies ... More
NLTK: The Natural Language ToolkitMay 17 2002NLTK, the Natural Language Toolkit, is a suite of open source program modules, tutorials and problem sets, providing ready-to-use computational linguistics courseware. NLTK covers symbolic and statistical natural language processing, and is interfaced ... More
An Integrated Framework for Treebanks and Multilayer AnnotationsApr 03 2002Treebank formats and associated software tools are proliferating rapidly, with little consideration for interoperability. We survey a wide variety of treebank structures and operations, and show how they can be mapped onto the annotation graph model, ... More
Annotation graphs as a framework for multidimensional linguistic data analysisJul 05 1999In recent work we have presented a formal framework for linguistic annotation based on labeled acyclic digraphs. These `annotation graphs' offer a simple yet powerful method for representing complex annotation structures incorporating hierarchy and overlap. ... More
Discussion of: Statistical analysis of an archeological find--skeptical counting challenges to an archaeological findApr 01 2008Discussion of ``Statistical analysis of an archeological find'' by Andrey Feuerverger [arXiv:0804.0079]
Many uses, many annotations for large speech corpora: Switchboard and TDT as case studiesJul 13 2000This paper discusses the challenges that arise when large speech corpora receive an ever-broadening range of diverse and distinct annotations. Two case studies of this process are presented: the Switchboard Corpus of telephone conversations and the TDT2 ... More
The Effects of Substructure on Galaxy Cluster Mass DeterminationsMar 08 1995Mar 09 1995Although numerous studies of individual galaxy clusters have demonstrated the presence of significant substructure, previous studies of the distribution of masses of galaxy clusters determined from optical observations have failed to explicitly correct ... More
Damped Lyman-alpha absorbers as a probe of stellar feedbackMay 15 2014Sep 16 2014We examine the abundance, clustering and metallicity of Damped Lyman-alpha Absorbers (DLAs) in a suite of hydrodynamic cosmological simulations using the moving mesh code AREPO. We incorporate models of supernova and AGN feedback, as well as molecular ... More
Subhalo Demographics in the Illustris Simulation: Effects of Baryons and Halo-to-Halo VariationNov 23 2016Mar 12 2019We study the abundance of subhaloes in the hydrodynamical cosmological simulation Illustris, which includes both baryons and dark matter in a $\Lambda$CDM volume 106.5 Mpc a side. We compare Illustris to its dark matter-only (DMO) analogue, Illustris-Dark, ... More
Muon Hunter: a Zooniverse projectFeb 24 2018The large datasets and often low signal-to-noise inherent to the raw data of modern astroparticle experiments calls out for increasingly sophisticated event classification techniques. Machine learning algorithms, such as neural networks, have the potential ... More
The nature of the ASCA/INTEGRAL source AX J183039-1002: a new Compton-thick AGN?Jan 16 2009We report on the identification of the X/soft gamma-ray source AX J183039-1002 detected with ASCA and INTEGRAL/IBIS. The source, which has an observed 20-100 keV flux of about 8.6 x 10^-11 erg/cm^2/s, is inside a diffuse radio supernova remnant (SNR) ... More
IGR J16393-4643: a new heavily-obscured X-ray pulsarOct 05 2005Oct 06 2005An analysis of the high-energy emission from IGR J16393-4643 (=AX J1639.0-4642) is presented using data from INTEGRAL and XMM-Newton. The source is persistent in the 20-40 keV band at an average flux of 5.1x10^-11 ergs/cm2/s, with variations in intensity ... More
Using the ROSAT Bright Source Catalogue to find Counterparts for IBIS/ISGRI Survey SourcesFeb 08 2005The IBIS/ISGRI first year galactic plane survey has produced a catalogue containing 123 hard X-ray sources visible down to a flux limit of a few milliCrabs. The point source location accuracy of typically 1-3 arcminutes has allowed the counterparts for ... More
The INTEGRAL/IBIS AGN catalogue I: X-ray absorption properties versus optical classificationJul 20 2012In this work we present the most comprehensive INTEGRAL AGN sample which lists 272 objects. Here we mainly use this sample to study the absorption properties of active galaxies, to probe new AGN classes and to test the AGN unification scheme. We find ... More
A review of progress in the physics of open quantum systems: theory and experimentJul 30 2015Nov 05 2015This Report explores recent advances in our understanding of the physics of open quantum systems (OQSs) which consist of some localized region that is coupled to an external environment. Examples of such systems may be found in numerous areas of physics ... More
Comment on ``New Class of Resonances at the Edge of the Two-Dimensional Electron Gas:'' self-consistent electronic structureNov 01 1996Self-consistent electronic structure calculations, for devices recently fabricated and studied by Zhitenev et al. for capacitance spectroscopy in the quantum Hall regime, demonstrate that reproducible resonances in the coupling between adiabatically free ... More
Fading Features Found in the Kinematics of the Far-Reaching Milky Way Stellar HaloJul 01 2015We test the long-term kinematical stability of a Galactic stellar halo model, due to Kafle, et al. (2012), who study the kinematics of approximately 5000 blue horizontal branch (BHB) stars in the Sloan Digital Sky Survey (SDSS). The velocity dispersion ... More
IGR J22517+2218=MG3 J225155+2217: a new gamma-ray lighthouse in the distant UniverseSep 19 2007We report on the identification of a new soft gamma ray source, namely IGR J22517+2218, detected with IBIS/INTEGRAL. The source, which has an observed 20-100 keV flux of ~4 x10^-11 erg cm-2 s-1, is spatially coincident with MG3 J225155+2217, a quasar ... More
High-redshift blazar identification for Swift J1656.3-3302Jan 18 2008We report on the high-redshift blazar identification of a new gamma-ray source, Swift J1656.3-3302, detected with the BAT imager onboard the Swift satellite and the IBIS instrument on the INTEGRAL satellite. Follow-up optical spectroscopy has allowed ... More
A 420 day X-ray/optical modulation and extended X-ray dips in the short-period transient Swift J1753.5-0127Mar 25 2013May 02 2013We have discovered a \sim420d modulation, with associated X-ray dips, in RXTE-ASM/MAXI/Swift-BAT archival light-curves of the short-period (3.2h) black-hole X-ray transient, Swift J1753.5-0127. This modulation only appeared at the end of a gradual rebrightening, ... More
The AGN nature of 11 out of 12 Swift/RXTE unidentified sources through optical and X-ray spectroscopyJun 23 2007The Swift Burst Alert Telescope (BAT) is performing a high Galactic latitude survey in the 14-195 keV band at a flux limit of ~10^{-11} erg cm^{-2} s^{-1}, leading to the discovery of new high energy sources, most of which have not so far been properly ... More
INTEGRAL detection of the pulsar wind nebula in PSR J1846-0258Oct 30 2007We communicate the detection of soft (20--200 keV) gamma-rays from the pulsar and pulsar wind nebula of PSR J1846-0258 and aim to identify the component of the system which is responsible for the gamma-ray emission. To pinpoint the source of gamma-ray ... More
IGR J18483-0311: an accreting X-ray pulsar observed by INTEGRALFeb 19 2007IGR J18483-0311 is a poorly known transient hard X-ray source discovered by INTEGRAL during observations of the Galactic Center region performed between 23--28 April 2003. Aims: To detect new outbursts from IGR J18483-0311 using INTEGRAL and archival ... More
Gamma-Ray All Sky Imaging with BATSEAug 23 2004The BATSE mission aboard CGRO observed the whole sky for 9 years in the 20 keV - 2 MeV energy band. Flat-fielding of the temporal variations in the background present in the data set has been accomplished through a GEANT3 Monte-Carlo simulation - the ... More
Multi-wavelength observations of the Be/X-ray binary IGR J01217-7257 (=SXP 2.16) during outburstDec 02 2016We present simultaneous, multi-wavelength observations of the Small Magellanic Cloud Be/XRB IGR J01217-7257 (=SXP 2.16) during outbursts in 2014, 2015 and 2016. We also present the results of RXTE observations of the Small Magellanic Cloud during which ... More