bluuebunny/crossref_metadata_2025_split huggingface dataset:
Are radio‐loud Broad Absorption Line Quasars young sources?
Authors: Montenegro‐Montes F.M. , Mack K.‐H. , Benn C.R. , Carballo R. , González‐Serrano J.I. , Holt J. , Jiménez‐Luján F. 
Published: February 2009

AbstractStudying Broad Absorption Line Quasars (BAL QSOs) is interesting because they probe the physics of the AGN environment, and because AGN outflows are important ingredients in many recent astrophysical puzzles. In the last decade, a substantial population of radio BAL QSOs was discovered and we have started a characterisation of the radio‐loud BAL QSO population studying their radio spectra, radio morphology and polarisation properties. Our high‐resolution radio maps show that BAL QSOs are compact radio sources with projected linear sizes below 1 kpc. Most BAL QSOs in our sample are unpolarised or weakly polarised at 8.4 GHz. They display convex radio spectra which typically flatten at low frequencies and become steeper at high frequencies, i.e. above 20 GHz. Many of these characteristics are common to the population of young radio sources, like Compact Steep Spectrum (CSS) or Gigahertz‐Peaked Spectrum (GPS) sources. The above supports the hypothesis that BAL QSOs might be related to the initial stages in the AGN evolution (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Probing the nature of multiple lobe‐like emissions in 3C 84
Authors: Nagai H. , Asada K. , Doi A. , Kameno S. , Inoue M. 
Published: February 2009

AbstractThe bright radio source 3C 84 has a CSO‐like feature in the central 10‐pc scale with extended emissions on scale up to kpc. Our kinematic and synchrotron age measurements support that the innermost feature is a CSO formed by recent restarted activity before the radio emission that originated in the earlier activities has completely faded. The average rate of the jet power of the innermost feature over the source age is at least ∼1044 erg s–1. Synchrotron age constraint for an outer lobe‐like feature beyond the central CSO indicates that this feature originates in the outburst from ∼1.3×105 years ago. Inferred duty cycle of the jet ejection is much shorter than the time scale expected from microquasars (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Radio source populations: Results from SDSS
Authors: Best P.N. 
Published: February 2009

AbstractThis contribution provides a review of our current understanding of radio source populations and their host galaxies, as derived from studies of the local Universe, in particular using the Sloan Digital Sky Survey. Evidence is presented that low luminosity radio sources are fundamentally distinct objects to high radio luminosity sources and optically or X‐ray selected AGN, suggesting that these are fuelled by a different mechanism. The low‐luminosity radio sources are argued to be fuelled by the accretion of hot gas from their surrounding X‐ray haloes, and this offers a potential feedback loop via which the radio‐loud AGN can control the cooling of the hot gas, and thus the growth of their host galaxy. The energetic output of the radio sources is derived in order to show that this is indeed feasible. It is emphasised that the difference between these two modes of AGN fuelling is distinct from that of the two different radio morphological classes of radioloud AGN (Fanaroff‐Riley classes 1 and 2). The origin of the FR‐dichotomy is investigated using Sloan data, and argued to be associated with the environment and evolution of the radio sources. Finally, the role of CSS and GPS sources within this picture is discussed (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A survey of Low Luminosity Compact sources
Authors: Kunert‐Bajraszewska M. , Thomasson P. 
Published: February 2009

AbstractBased on the FIRST and SDSS catalogues a flux density limited sample of weak Compact Steep Spectrum (CSS) sources with radio luminosity below 1026WHz–1 at 1.4 GHz has been constructed. Our previous multifrequency observations of CSS sources have shown that low luminosity small‐scale objects can be strong candidates for compact faders. This finding supports the idea that some small‐size radio sources are short‐lived phenomena because of a lack of significant fuelling. They never ‘grow up’ to become FRI or FRII objects. This new sample marks the start of a systematic study of the radio properties and morphologies of the population of low luminosity compact (LLC) objects. An investigation of this new sample should also lead to a better understanding of compact faders. In this paper, the results of the first stage of the new project – the L‐band MERLIN observations of 44 low luminosity CSS sources are presented (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An “incomplete sample” of CSSs observed with the VLA
Authors: Rossetti A. , Mantovani F. , Junor W. , Saikia D.J. , Salter C. 
Published: February 2009

AbstractA sample of 26 Compact Steep Spectrum sources selected from the original list drawn up by Dallacasa & Stanghellini (1990) have been observed with the VLA A‐array at X, U, and K bands. Images have been produced in both total intensity and polarisation at four widely‐spaced frequencies with the aim of deriving linear polarisation parameters. We present preliminary polarisation results on source fractional polarisation and electric vector angle at X and U bands. These new information will be completed with available archive data in order to perform a polarimetric analysis of a complete CSS sample (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High Frequency Peakers: The faint sample
Authors: Stanghellini C. , Dallacasa D. , Orienti M. 
Published: February 2009

AbstractWe present a sample of sources with convex radio spectra peaking at frequencies above a few GHz, known as “High Frequency Peakers” (HFPs). A “bright” sample with a flux density limit of 300 mJy at 5 GHz has been presented by Dallacasa et al. (2000). Here we present the “faint” sample with flux density between 50 and 300 mJy at 5 GHz, restricted to the area around the North Galactic Cap, where the FIRST catalogue is available. The candidates have been observed with the VLA at several frequencies ranging from 1.4 to 22 GHz, in order to derive a simultaneous radio spectrum. The final list of confirmed HFP sources consists of 61 objects (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical spectra of 15 Low Luminosity Compact Sources and the formation of jets
Authors: Buttiglione S. , Celotti A. , Capetti A. , Dallacasa D. , D'Odorico V. , Giovannini G. 
Published: February 2009

AbstractWe present the results of optical spectroscopy of 15 compact radio sources, selected to be among the lowest luminosity objects and expected to evolve into FR I radio galaxies. The aim of the work is to exploit the emission line characteristics as indicators of the nuclear activity – in terms of accretion properties – during the early stages of the production of jets. The emission line ratios identify most Low Luminosity Compact Sources (LLCSs) as low excitation galaxies, similar to evolved FR I. Also in terms of their optical – radio properties they appear to be indistinguishable from FR I. These findings support the view that jets could be produced by nuclei accreting both at high and low rates (and/or radiatively efficient and inefficient discs). They also argue against the idea that FRI represent a late stage after a powerful FR II phase (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Interferometer observations of molecular gas in radio galaxies
Authors: García‐Burillo S. , Combes F. , Usero A. , Fuente A. 
Published: February 2009

AbstractWe present the first results of a high‐resolution study of the distribution and kinematics of molecular gas in two nearby radio galaxies, 4C 31.04 and 3C 293, representative of two different stages of evolution in radio‐loud active galactic nuclei (AGN). These observations, conducted with the IRAM Plateau de Bure Interferometer (PdBI), map with unprecedented spatial resolution (∼0.5′–1′) and sensitivity the emission and absorption of key molecular species such as CO, HCN and HCO+. We report on the detection of a kinematically disturbed and massive (Mgas ∼ 1010 M⊙) molecular/dusty disk of ∼1.4 kpc‐size fueling the central engine of the compact symmetric object (CSO) 4C 31.04.We also report on the detection of a massive (Mgas ∼ 1010 M⊙) regularly rotating ∼7 kpc‐size disk in the FR II radio galaxy 3C 293. A complex system of molecular line absorptions is detected against the mm‐continuum source of this galaxy (AGN and jet). We compare the properties of the molecular disks in the two sources and discuss them in the light of the different theories describing the evolution of radio galaxies (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
H2O maser and a plasma obscuring torus in the radio galaxy NGC 1052
Authors: Sawada‐Satoh S. , Kameno S. , Nakamura K. , Namikawa D. , Shibata K. M. , Inoue M. 
Published: February 2009

AbstractWe present multi‐frequency simultaneous VLBA observations at 15, 22 and 43 GHz towards the nucleus of the nearby radio galaxy NGC 1052. These three continuum images reveal a double‐sided jet structure, whose relative intensity ratios imply that the jet axis is oriented close to the sky plane. The steeply rising spectra at 15–43 GHz at the inner edges of the jets strongly suggest that synchrotron emission is absorbed by foreground thermal plasma. We detected H2O maser emission in the velocity range of 1550–1850 km s–1, which is redshifted by 50–350 km s–1 with respect to the systemic velocity of NGC 1052. The redshifted maser gas appears projected against both sides of the jet, similar to the H I seen in absorption. The H2O maser gas is located where the free‐free absorption opacity is large. This probably implies that the masers in NGC 1052 are associated with a circumnuclear torus or disk as in the nucleus of NGC 4258. Such circumnuclear structure can be the sense of accreting onto the central engine (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Estimating black hole masses in young radio sources using CFHT spectroscopy
Authors: Gu M.F. , Pak S. , Ho L.C. 
Published: February 2009

AbstractThe correlation between black hole masses and stellar velocity dispersions provides an efficient method to determine the masses of black holes in active galaxies. We obtained optical spectra of a Compact‐Steep‐Spectrum (CSS) galaxy 4C +29.70, using the Canada‐France‐Hawaii Telescope (CFHT) equipped with OSIS, in 2003 August 6. Several stellar absorption features, such asMg I (5175 Å), Ca E band (5269 Å) and Na D (5890 Å), were detected in the spectra. The stellar velocity dispersion, σ, of the host galaxy, measured from absorption features is ≈250 km s–1. If 4C +29.70 follows the MBH‐σ relation established for nearby galaxies, then its central black hole has a mass of ≈3.3 × 108 M⊙. In combination with the black hole masses of seven GPS galaxies in Snellen et al. (2003), we find that the average black hole mass of these eight young radio sources is smaller than that of the Bettoni et al. (2003) sample of extended radio galaxies. This may indicate that young radio sources are likely at the early evolutionary stage of radio galaxies, at which the central black holes may still undergo rapid growth. However, this needs further investigations (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High energy emission from AGN cocoons in clusters of galaxies
Authors: Kino M. , Kawakatu N. , Ito H. , Nagai H. 
Published: February 2009

AbstractGamma‐ray emission from cocoons of young radio galaxies is predicted. Considering the process of adiabatic injection of the shock dissipation energy and mass of the relativistic jet into the cocoon, we find that the thermal electron temperature of the cocoon is typically predicted to be of the order of ∼MeV, and is determined only by the bulk Lorentz factor of the jet. Together with the time‐dependent dynamics of the cocoon expansion, we find that young cocoons can yield thermal bremsstrahlung emissions at energies ∼MeV. Hotter cocoons (i.e., GeV) for younger sources are also discussed (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A multi‐wavelength view of the archetypical CSS radio galaxy 3C303.1: Evidence for shocks and induced star formation
Authors: O'Dea C.P. 
Published: February 2009

AbstractI discuss multi‐wavelength data on the archetypal CSS radio galaxy 3C303.1. The radio source is sub‐galactic in scale where it can directly affect the ISM of the host galaxy. The emission line kinematics and ionization diagnostics are consistent with energy input from shocks driven by the radio source. The Spitzer IRS spectrum indicates that star formation is occurring in the host galaxy. The HST/ACS/HRC UV image shows UV light which is aligned with the radio source axis. I suggest that the UV light is from young stars which have been triggered by the radio lobes. XMM observations detect the ISM of the host galaxy with a temperature of 0.8 keV plus an additional component whose properties are not well defined. I suggest the second component is a hot shocked gas (T = 45 keV) consistent with a Mach number of 13 for the expanding bow shock. Thus, the multi‐wavelength data give a consistent picture in which the radio source drives shocks into the ISM which ionize dense clouds, trigger star formation, and shock heat the hot component of the ISM to very high temperature. These observations demonstrate that radio sources can provide significant feedback to their host galaxy (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
X‐ray emission from GPS and CSS sources
Authors: Siemiginowska A. 
Published: February 2009

AbstractMany X‐ray observations of GigaHertz Peaked Spectrum and Compact Steep Spectrum sources have been made with Chandra X‐ray Observatory and XMM‐Newton Observatory over the last few years. The X‐ray spectra contribute the important information to the total energy distribution of the compact radio sources. In addition the spatial resolution of Chandra allows for studies of the X‐ray morphology of these sources on arcsec scales and provide a direct view of their environments. This paper gives a review of the current status of the X‐ray observations and their contribution to our understanding of the nature of these compact radio sources. It also describes primary physical processes that lead to the observed X‐ray emission and summarize X‐ray emission properties expected from interactions between an expanding radio source and the intergalactic environment (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Evolution of radio galaxies
Authors: Kaiser C.R. 
Published: February 2009

AbstractThe dynamical evolution of FRII‐type radio galaxies can be successfully modelled employing purely analytical techniques. The solutions change depending on the lobe size relative to the characteristic length scale for individual objects, resulting in three distinct regimes. By far the best understood regime is that of large sources. For these we can also construct emission models predicting the evolution of the radio luminosity as a function of source size or age and a limited number of source parameters. We can use such models to constrain the evolution of the radio galaxy population as a whole. Building on these successes, we find some hints that radio galaxies can change their morphologies between the two FR classes. Better emission models for all length scales and models for FRI‐type objects are now needed to progress our understanding of all evolutionary branches of radio galaxies (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling the broad‐band spectra of X‐ray emitting GPS galaxies
Authors: Ostorero L. , Moderski R. , Stawarz Ł. , Begelman M.C. , Diaferio A. , Kowalska I. , Kataoka J. , Wagner S.J. 
Published: February 2009

AbstractThe study of the broad‐band emission of GHz‐Peaked‐Spectrum (GPS) radio galaxies is a powerful tool to investigate the physical processes taking place in the central, kpc‐sized region of their active hosts, where the jets propagate and the lobes expand, interacting with the surrounding interstellar medium (ISM). We recently developed a new dynamical‐radiative model to describe the evolution of the GPS phenomenon (Stawarz et al. 2008): as the relativistic jets propagate through the ISM, gradually engulfing narrow‐line emitting gas clouds along their way, the electron population of the expanding lobes evolves, emitting synchrotron light, as well as inverse‐Compton radiation via up‐scattering of the photon fields from the host galaxy and its active nucleus. The model, which successfully reproduces the key features of the GPS radio sources as a class, provides a description of the evolution of their spectral energy distribution (SED) with the lobes' expansion, predicting significant and complex X‐ray to γ ‐ray emission.We apply here the model to the broad‐band SED's of a sample of known, X‐ray emitting GPS galaxies, and show that (i) the free‐free absorption mechanism enables us to reproduce the radio continuum at frequencies below the turnover; (ii) the lobes' non‐thermal, inverse‐Compton emission can account for the observed X‐ray spectra, providing a viable alternative to the thermal, accretion‐dominated scenario. We also show that, in our sample, the relationship between the X‐ray and radio hydrogen column densities, NH and NHI, is suggestive of a positive correlation, which, if confirmed, would support the scenario of high‐energy emitting lobes (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Interaction of radio jets with clouds in the ambient medium: Numerical simulations
Authors: Jeyakumar S. 
Published: February 2009

AbstractHydrodynamical simulations of jets interacting with clouds moving in the ambient medium of the host galaxy are presented. Clouds with sizes of the order of the jet diameter and smaller, crossing the path of the jet with different speeds are considered. In the case of slow moving clouds the jet is stopped over the brief period of time taken by the cloud to cross the jet. The jet maintains its general morphology in the case of fast moving clouds. Erosion of the clouds leads to redistribution of cloud material to large distances. Such interaction may explain the large outflow velocities observed from pc to kpc scales in the compact radio sources (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
RubAre symmetric radio spectra of some GPS/HFP sources related to a statistical acceleration mechanism?rik
Authors: Maselli A. , Massaro E. 
Published: February 2009

AbstractWe present the results of a new spectral analysis of a sample of HFPs. We took from literature simultaneous radio measurements at various epochs and studied the symmetry of flux distribution around the peak frequency by means of a logparabolic fit.We found that a large fraction of spectra are symmetric and propose that this property may be a consequence of statistical acceleration (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exact, Distribution Free Confidence Intervals for Late Effects in Censored Matched Pairs
Authors: Daniel Shoshana R. 
Published: February 2009

AbstractWhen comparing censored survival times for matched treated and control subjects, a late effect on survival is one that does not begin to appear until some time has passed. In a study of provider specialty in the treatment of ovarian cancer, a late divergence in the Kaplan–Meier survival curves hinted at superior survival among patients of gynecological oncologists, who employ chemotherapy less intensively, when compared to patients of medical oncologists, who employ chemotherapy more intensively; we ask whether this late divergence should be taken seriously. Specifically, we develop exact, permutation tests, and exact confidence intervals formed by inverting the tests, for late effects in matched pairs subject to random but heterogeneous censoring. Unlike other exact confidence intervals with censored data, the proposed intervals do not require knowledge of censoring times for patients who die. Exact distributions are consequences of two results about signs, signed ranks, and their conditional independence properties. One test, the late effects sign test, has the binomial distribution; the other, the late effects signed rank test, uses nonstandard ranks but nonetheless has the same exact distribution as Wilcoxon's signed rank test. A simulation shows that the late effects signed rank test has substantially more power to detect late effects than do conventional tests. The confidence statement provides information about both the timing and magnitude of late effects (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Evaluating Co‐primary Endpoints Collectively in Clinical Trials
Authors: Li Qian H. 
Published: February 2009

AbstractOften a treatment is assessed by co‐primary endpoints so that a comprehensive picture of the treatment effect can be obtained. Co‐primary endpoints can be different medical assessments angled at different aspects of a disease, therefore, are used collectively to strengthen evidence for the treatment effect. It is common sense that if a treatment is ineffective, the chance to show that the treatment is effective in all co‐primary endpoints should be small. Therefore, it may not be necessary to require all the co‐primary endpoints to be statistically significant at the 1‐sided 0.025 level to control the error rate of wrongly approving an ineffective treatment. Rather it is reasonable to allow certain variation for the p ‐values within a range close to 0.025. In this paper, statistical methods are developed to derive decision rules to evaluate co‐primary endpoints collectively. The decision rules control the error rate of wrongly accepting an ineffective treatment at the level of 0.025 for a study and the error rate at a slightly higher level for a treatment that works for all the co‐primary endpoints except perhaps one. The decision rules also control the error rates for individual endpoints. Potential applications in clinical trials are presented (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Finite Mixture Models for Mapping Spatially Dependent Disease Counts
Authors: Alfó Marco , Nieddu Luciano , Vicari Donatella 
Published: February 2009

AbstractA vast literature has recently been concerned with the analysis of variation in disease counts recorded across geographical areas with the aim of detecting clusters of regions with homogeneous behavior. Most of the proposed modeling approaches have been discussed for the univariate case and only very recently spatial models have been extended to predict more than one outcome simultaneously. In this paper we extend the standard finite mixture models to the analysis of multiple, spatially correlated, counts. Dependence among outcomes is modeled using a set of correlated random effects and estimation is carried out by numerical integration through an EM algorithm without assuming any specific parametric distribution for the random effects. The spatial structure is captured by the use of a Gibbs representation for the prior probabilities of component membership through a Strauss‐like model. The proposed model is illustrated using real data (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)