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Sep 19, 2013
09/13
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G. B. Taylor
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Multi-frequency polarimetry with the Very Long Baseline Array (VLBA) telescope has revealed absolute Faraday Rotation Measures (RMs) in excess of 1000 rad/m/m in the central regions of 7 out of 8 strong quasars studied (e.g., 3C 273, 3C 279, 3C 395). Beyond a projected distance of ~20 pc, however, the jets are found to have |RM| < 100 rad/m/m. Such sharp RM gradients cannot be produced by cluster or galactic-scale magnetic fields, but rather must be the result of magnetic fields organized...
Source: http://arxiv.org/abs/astro-ph/9911414v1
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Jul 20, 2013
07/13
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G. B. Taylor; J. Granot
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The multi-wavelength observations of the 2004 December~27 Giant Flare (GF) from SGR 1806-20 and its long-lived radio afterglow are briefly reviewed. The GF appears to have been produced by a dramatic reconfiguration of the magnetic field near the surface of the neutron star, possibly accompanied by fractures in the crust. The explosive release of over 10^46 ergs (isotropic equivalent) powered a one-sided mildly relativistic outflow. The outflow produced a new expanding radio nebula, that is...
Source: http://arxiv.org/abs/astro-ph/0609595v1
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Sep 21, 2013
09/13
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T. Venturi; G. B. Taylor
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Multifrequency polarimetric observations made with the Very Long Baseline Array of the quasar 3C216 reveal the presence of Faraday rotation measures (RMs) in excess of 2000 rad/m**2 in the source rest frame, in the arc of emission located at ~ 140 mas from the core. Rotation measures in the range -300 - +300 rad/m**2 are detected in the inner 5 mas (~30 parsecs). while the rotation measures near the core can be explained as due to a magnetic field in the narrow line region, we favor the...
Source: http://arxiv.org/abs/astro-ph/9907321v1
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Sep 19, 2013
09/13
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G. B. Taylor; R. Zavala
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We report on multi-frequency polarimetry Very Long Baseline Interferometry observations of active galactic nuclei using the VLBA. These observations are used to construct images of the Faraday Rotation Measure (RM) in J1613+342, Mrk 501, 3C 371, and BL Lac. Despite having resolved the jets in total intensity and polarization for three of these sources no RM gradients are found. This is in contrast to the large fraction of sources with RM gradients now claimed in the literature, and invoked as...
Source: http://arxiv.org/abs/1009.3465v1
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Sep 19, 2013
09/13
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A. B. Peck; G. B. Taylor
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The class of radio sources known as Compact Symmetric Objects (CSOs) is of particular interest in the study of the evolution of radio galaxies. CSOs are thought to be young (probably ~10^4 years), and a very high fraction of them exhibit HI absorption toward the central parsecs. The HI, which is thought to be part of a circumnuclear torus of accreting gas, can be observed using the VLBA with high enough angular resolution to map the velocity field of the gas. This velocity field provides new...
Source: http://arxiv.org/abs/astro-ph/9911301v1
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Sep 22, 2013
09/13
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C. D. Fassnacht; G. B. Taylor
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We present results from the first intensive monitoring campaign of a sample of Compact Symmetric Objects (CSOs). We observed seven CSOs at 8.5 GHz over a period of eight months, with an average spacing between observations of 2.7 days. Our results show that, as predicted, the flux densities of the CSOs are extremely stable; the mean RMS variability of the sample was 0.7% in flux density. The low variability of the CSOs makes them excellent flux density calibrators at this frequency. We...
Source: http://arxiv.org/abs/astro-ph/0106001v1
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Sep 19, 2013
09/13
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A. B. Peck; G. B. Taylor
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Recent VLBI observations have identified several compact radio sources which have symmetric structures on parsec scales, and exhibit HI absorption which appears to be associated with the active nucleus. These sources are uniquely well suited to investigations into the physics of the central engines, in particular to studies of the kinematics of the gas within 100 pc of the core. In these compact sources, it is reasonable to assume that this circumnuclear material is accreting onto, and...
Source: http://arxiv.org/abs/astro-ph/9911302v1
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Sep 19, 2013
09/13
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R. T. Zavala; G. B. Taylor
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Rotation measure observations of 9 quasars, 4 BL Lacertae objects, and 3 radio galaxies are presented. The rest frame rotation measures in the cores of the quasars and the jets of the radio galaxy M87 are several thousand radians per meter squared. The BL Lacertae objects and the jets of the quasars have rest frame rotation measures of a few hundred radians per meter squared. A nuclear rotation measure of 500 radians per meter squared in the rest frame is suggested as the dividing line between...
Source: http://arxiv.org/abs/astro-ph/0302367v1
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Sep 18, 2013
09/13
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C. L. Carilli; G. B. Taylor
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Images of neutral Hydrogen 21cm absorption and radio continuum emission at 1.4 GHz from Mrk 273 were made using the Very Long Baseline Array and Very Large Array. These images reveal a gas disk associated with the northern nuclear region with a diameter of 0.5'' (370 pc), at an inclination angle of 53deg. The radio continuum emission is composed of a diffuse component plus a number of compact sources. This morphology resembles those of nearby, lower luminosity starburst galaxies. These images...
Source: http://arxiv.org/abs/astro-ph/0002186v1
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Sep 19, 2013
09/13
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A. B. Peck; G. B. Taylor
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We present results of multifrequency polarimetric VLBA observations of 34 compact radio sources. The observations are part of a large survey undertaken to identify CSOs Observed in the Northern Sky (COINS). Compact Symmetric Objects (CSOs) are of particular interest in the study of the physics and evolution of active galaxies. Based on VLBI continuum surveys of ~2000 compact radio sources, we have defined a sample of 52 CSOs and CSO candidates. In this paper, we identify 18 previously known...
Source: http://arxiv.org/abs/astro-ph/9912189v1
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Sep 18, 2013
09/13
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C. L. Carilli; G. B. Taylor
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Magnetic fields in galaxy clusters have been measured using a variety of techniques, including: studies of synchrotron relic and halo radio sources within clusters, studies of inverse Compton X-ray emission from clusters, surveys of Faraday rotation measures of polarized radio sources both within and behind clusters, and studies of Cluster Cold Fronts in X-ray images. These measurements imply that most cluster atmospheres are substantially magnetized, with typical field strengths of order 1...
Source: http://arxiv.org/abs/astro-ph/0110655v1
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Sep 24, 2013
09/13
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R. T. Zavala; G. B. Taylor
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Multifrequency polarimetry with the VLBA confirms the previously reported time-varying Faraday rotation measure (RM) in the quasar 3C-279. Variability in the RM and electric vector position angle (EVPA) of the jet component (C4) is seen making it an unreliable absolute EVPA calibrator. 3C-273 is also shown to vary its RM structure on 1.5 year time-scales. Variation in the RM properties of quasars may result from a Faraday screen which changes on time-scales of a few years, or from the motion of...
Source: http://arxiv.org/abs/astro-ph/0103180v1
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Sep 22, 2013
09/13
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G. B. Taylor; A. B. Peck
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We present results of multifrequency polarimetric VLBA observations of 20 compact radio sources. The observations represent the northern and southern extensions of a large survey undertaken to identify Compact Symmetric Objects (CSOs) Observed in the Northern Sky (COINS). CSOs are young radio galaxies whose jet axes lie close to the plane of the sky, and whose appearance is therefore not dominated by relativistic beaming effects. The small linear sizes of CSOs make them valuable for studies of...
Source: http://arxiv.org/abs/astro-ph/0307151v1
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Sep 18, 2013
09/13
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A. B. Peck; G. B. Taylor
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eye 49
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A number of extragalactic radio sources which exhibit symmetric jets on parsec scales have now been found to have neutral hydrogen absorption at or near the systemic velocities of their host galaxies. Understanding the spatial distribution and kinematics of the HI detected toward the central parsecs of these sources provides an important test of unified schemes for AGN. We present results of Global VLBI Network observations of the redshifted 21 cm HI line toward the Compact Symmetric Object...
Source: http://arxiv.org/abs/astro-ph/0105310v1
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Sep 18, 2013
09/13
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R. T. Zavala; G. B. Taylor
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Using high frequency (12-22 GHz) VLBA observations we confirm the existence of a Faraday rotation measure gradient of ~ 500 rad/m^2/mas transverse to the jet axis in the quasar 3C 273. The gradient is seen in two epochs spaced roughly six months apart. This stable transverse rotation measure gradient is expected if a helical magnetic field wraps around the jet. The overall order to the magnetic field in the inner projected 40 parsecs is consistent with a helical field. However, we find an...
Source: http://arxiv.org/abs/astro-ph/0505357v1
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Jul 20, 2013
07/13
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A. B. Peck; G. B. Taylor
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One of the most important problems in the study of AGN is understanding the detailed geometry, physics, and evolution of the central engines and their environments. The leading models involve an accretion disk and torus around a central black hole. Much of this torus should be comprised of atomic gas, detectable in absorption toward the bright inner radio jets. In the last few years, a number of compact symmetric radio sources have been found to exhibit HI absorption, at or near the systemic...
Source: http://arxiv.org/abs/astro-ph/0009373v1
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Sep 20, 2013
09/13
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R. T. Zavala; G. B. Taylor
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Results from a survey of the parsec scale Faraday rotation measure properties for 40 quasars, radio galaxies and BL Lac objects are presented. Core rotation measures for quasars vary from approximately 500 to several thousand radians per meter squared. Quasar jets have rotation measures which are typically 500 radians per meter squared or less. The cores and jets of the BL Lac objects have rotation measures similar to those found in quasar jets. The jets of radio galaxies exhibit a range of...
Source: http://arxiv.org/abs/astro-ph/0405534v1
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Jul 20, 2013
07/13
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A. B. Peck; G. B. Taylor
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eye 50
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We present results of multifrequency polarimetric VLBA observations of 34 compact radio sources. The observations are part of a large survey undertaken to identify CSOs Observed in the Northern Sky (COINS). Based on VLBI continuum surveys of ~2000 compact radio sources, we have defined a sample of 52 CSOs and CSO candidates. Positive identification of CSOs is contingent upon acquiring multi-frequency observations in order to correctly identify the core of the source, which is expected to have a...
Source: http://arxiv.org/abs/astro-ph/0009372v1
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Sep 22, 2013
09/13
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R. T. Zavala; G. B. Taylor
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Parsec-scale Faraday rotation measure (RM) maps are presented for the radio galaxies M87, 3C 111, and 3C 120. These Very Long Baseline Array observations were made at 8, 12, and 15 GHz. M87 has an extreme RM distribution that varies from -4000 radians m^-2 to more than 9000 radians m^-2 across a projected distance of 0.3 pc in its jet. M87 has no polarized flux closer than 17 mas from the core. 3C 111 and 3C 120 both show polarized emission in their cores that is consistent with the...
Source: http://arxiv.org/abs/astro-ph/0201458v1
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Sep 24, 2013
09/13
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G. Giovannini; M. Giroletti; G. B. Taylor
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We present new Very Long Baseline Interferometry observations of the LINER galaxy NGC 4278 with a linear resolution of < 0.1 pc. Our radio data reveal a two sided structure, with symmetric S-shaped jets emerging from a flat spectrum core. By comparing the positions of the components in two epochs, we measure motions corresponding to apparent velocities < 0.2 c, and to ages in the range 8.3 - 65.8 years. From our measurements, we derive that NGC 4278 has mildly relativistic jets (beta...
Source: http://arxiv.org/abs/astro-ph/0412563v1
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Sep 19, 2013
09/13
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G. Giovannini; M. Giroletti; G. B. Taylor
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eye 57
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The goal of this work is a detailed study of the nearby, low power radio galaxy B2 1144+35B. For this purpose, we performed new Very Long Baseline Array (VLBA) and Very Large Array (VLA) observations. This source has several properties (bright, nearby, large range of spatial structures, visible counterjet, etc.) that make it an excellent astrophysical laboratory for the study of the evolution of radio jets. Here we report the detection of motion in the counterjet at 0.23 $\pm$ 0.07 c, which...
Source: http://arxiv.org/abs/0708.3902v1
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Sep 24, 2013
09/13
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M. Giroletti; G. B. Taylor; G. Giovannini
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We present new Very Long Baseline Interferometry observations of the LINER galaxy NGC 4278. The observations were taken with the Very Long Baseline Array (VLBA) and a single antenna of the Very Large Array (VLA) at 5 GHz and 8.4 GHz and have a linear resolution of
Source: http://arxiv.org/abs/astro-ph/0412204v1
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Sep 20, 2013
09/13
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M. Giroletti; G. Giovannini; G. B. Taylor
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We present sub-arcsecond resolution multi-frequency (8 and 22 GHz) VLA images of five low power compact (LPC) radio sources, and phase referenced VLBA images at 1.6 GHz of their nuclear regions. At the VLA resolution we resolve the structure and identify component positions and flux densities. The phase referenced VLBA data at 1.6 GHz reveals flat-spectrum, compact cores (down to a few milliJansky) in four of the five sources. The absolute astrometry provided by the phase referencing allows us...
Source: http://arxiv.org/abs/astro-ph/0506497v1
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Sep 19, 2013
09/13
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G. Giovannini; M. Giroletti; G. B. Taylor
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We have observed the BL Lac object Markarian 501 at 1.4 GHz with the High Sensitivity Array and at 86 GHz with the global VLBI mm array. Thanks to the great resolution and sensitivity provided by these instruments, we probe regions of the radio jets never accessed before. The new data at 1.4 GHz allow us to map the one-sided jet at large distances from the core, and to constrain jet properties thanks to the high jet to counter-jet brightness ratio. The 86 GHz data give us a high resolution...
Source: http://arxiv.org/abs/0708.3911v1
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Sep 22, 2013
09/13
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J. M. Marr; G. B. Taylor; F. Crawford
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eye 43
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We have observed the canonical gigahertz-peaked spectrum source 0108+388 with the VLBA at a range of frequencies above and below the spectral peak. The activity that dominates the radio emission from 0108+388, which is also classified as a Compact Symmetric Object, is thought to be less than 1000 years old. We present strong evidence that the spectral turnover in 0108+388 results from free-free absorption by non-uniform gas, possibly in the form of a disk in the central tens of parsecs.
Source: http://arxiv.org/abs/astro-ph/0011372v1
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Sep 18, 2013
09/13
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G. B. Taylor; D. H. Hough; T. Venturi
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We present sensitive, high dynamic range, Very Long Baseline Array (VLBA) polarimetric observations of the cores of three powerful radio galaxies: 3C166, 3C236 and 3C390.3. Significant polarization is detected in one source (3C166) allowing us to map out the Faraday Rotation Measure (RM) distribution and projected magnetic field direction. The inner jet of 3C166 is found to have a rest frame RM of -2300 rad/m**2, similar to those found in quasars cores. No polarized flux was detected from the...
Source: http://arxiv.org/abs/astro-ph/0105285v1
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Sep 19, 2013
09/13
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D. E. Harris; H. Krawczynski; G. B. Taylor
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During the course of an investigation on the interaction of the radio galaxy 3C129 and its ambient cluster gas, we found excess X-ray emission aligned with the northern radio jet. The emission extends from the weak X-ray core of the host galaxy approximately 2.5" to the first resolved radio knot. On a smaller scale, we have also detected a weak radio extension in the same position angle with the VLBA. Although all the evidence suggests that Doppler favoritism augments the emission of the...
Source: http://arxiv.org/abs/astro-ph/0206466v1
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Jul 20, 2013
07/13
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M. Giroletti; G. Giovannini; G. B. Taylor; R. Falomo
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eye 60
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We present new radio observations of 9 members of a sample of 29 nearby (z < 0.2) BL Lac objects. The new data have been obtained with the European VLBI Network and/or the MERLIN at 1.6 and 5 GHz and complement previous observations. For one object, the TeV source Mrk 421, we also present deep multi-epoch VLBA and Global VLBI data, which reveal a resolved diffuse jet, with clear signatures of limb brightening. We use the new and old data to estimate physical parameters of the jets of the...
Source: http://arxiv.org/abs/astro-ph/0604224v1
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Sep 22, 2013
09/13
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J. S. Sanders; A. C. Fabian; G. B. Taylor
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eye 101
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We present results from deep Chandra and XMM-Newton observations of the relaxed X-ray luminous galaxy cluster Abell 2204. We detect metallicity inhomogeneities in the intracluster medium on a variety of distance scales, from a ~12 kpc enhancement containing a few times 10^7 Msun of iron in the centre, to a region at 400 kpc radius with an excess of a few times 10^9 Msun. Subtracting an average surface brightness profile from the X-ray image yields two surface brightness depressions to the north...
Source: http://arxiv.org/abs/0811.0743v1
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Jul 20, 2013
07/13
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M. Giroletti; G. Giovannini; G. B. Taylor; R. Falomo
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eye 69
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We present a new sample of 30 nearby (z
Source: http://arxiv.org/abs/astro-ph/0406255v1
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Sep 23, 2013
09/13
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J. S. Sanders; A. C. Fabian; G. B. Taylor
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eye 41
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We examine the core of the X-ray bright galaxy cluster 2A 0335+096 using deep Chandra X-ray imaging and spatially-resolved spectroscopy, and include new radio observations. The set of around eight X-ray bright blobs in the core of the cluster, appearing like eggs in a bird's nest, contains multiphase gas from ~0.5 to 2 keV. The morphology of the coolest X-ray emitting gas at 0.5 keV temperature is similar to the Halpha emitting nebula known in this cluster, which surrounds the central galaxy....
Source: http://arxiv.org/abs/0904.1374v1
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Sep 18, 2013
09/13
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J. M. Wrobel; G. B. Taylor; P. C. Gregory
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The Jodrell Bank - VLA Astrometric Survey (JVAS) of flat-spectrum sources yielded a catalog of 2118 compact radio sources in the northern sky. Those sources are being used as phase calibrators for many synthesis arrays. JVAS suffers from a zone of avoidance because Galactic confusion prevented selection of flat-spectrum sources at $\mid b \mid < 2.5\arcdeg$. This confusion problem was overcome by selecting variable GB6 sources in the JVAS zone of avoidance. A subset of these sources were...
Source: http://arxiv.org/abs/astro-ph/0105334v1
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Sep 18, 2013
09/13
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A. B. Peck; G. B. Taylor; J. E. Conway
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We present results of VLA and VLBA observations of the 1.420 GHz neutral hydrogen absorption associated with the Compact Symmetric Object 1946+708 (z=0.101). We find significant structure in the gas on parsec scales. The peak column density in the HI (N_HI~2.2x10^23 cm^-2 (T_s/8000K)) occurs toward the center of activity of the source, as does the highest velocity dispersion (FWHM~350 \kms). In addition, we find that the continuum spectra of the various radio components associated with these...
Source: http://arxiv.org/abs/astro-ph/9811386v2
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Sep 23, 2013
09/13
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M. Giroletti; G. Giovannini; G. B. Taylor; R. Falomo
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eye 82
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We present new radio data completing the imaging for a sample of 30 nearby (z < 0.2) BL Lac objects on parsec and kiloparsec scale. The sample is composed of both high and low luminosity sources and it is therefore an ideal test bed for unified schemes in the low power regime. VLBI and VLA data are used, thus providing information on both extended and inner, beamed components. We find morphologies and jet parameters consistent with a parent population composed of FR I radio galaxies, i.e. in...
Source: http://arxiv.org/abs/astro-ph/0408213v1
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Sep 23, 2013
09/13
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G. Giovannini; E. Liuzzo; M. Giroletti; G. B. Taylor
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eye 61
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We present an update of the parsec scale properties of the Bologna Complete Sample consisting of 95 radio sources with z $
Source: http://arxiv.org/abs/0903.5408v1
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Sep 20, 2013
09/13
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E. Liuzzo; G. Giovannini; M. Giroletti; G. B. Taylor
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eye 49
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We present new VLBI observations at 5 GHz of a complete sample of Brightest Cluster Galaxies (BCGs) in nearby Abell Clusters (distance class
Source: http://arxiv.org/abs/1002.1380v1
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Sep 22, 2013
09/13
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E. Liuzzo; G. Giovannini; M. Giroletti; G. B. Taylor
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eye 39
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To study statistical properties of different classes of sources, it is necessary to observe a sample that is free of selection effects. To do this, we initiated a project to observe a complete sample of radio galaxies selected from the B2 Catalogue of Radio Sources and the Third Cambridge Revised Catalogue (3CR), with no selection constraint on the nuclear properties. We named this sample "the Bologna Complete Sample" (BCS). We present new VLBI observations at 5 and 1.6 GHz for 33...
Source: http://arxiv.org/abs/0908.4391v1
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Sep 19, 2013
09/13
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L. K. Pollack; G. B. Taylor; R. T. Zavala
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We present VLBA observations and a statistical analysis of 5 GHz VLBI polarimetry data from 177 sources in the Caltech-Jodrell Bank flat-spectrum (CJF) survey. The CJF survey, a complete, flux-density-limited sample of 293 extragalactic radio sources, gives us the unique opportunity to compare a broad range of source properties for quasars, galaxies and BL Lacertae objects. We focus primarily on jet properties, specifically the correlation between the jet axis angle and the polarization angle...
Source: http://arxiv.org/abs/astro-ph/0302211v1
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Jul 20, 2013
07/13
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A. B. Peck; G. B. Taylor; K. M. Menten
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In the last several years, a number of compact extragalactic radio sources have been found to exhibit neutral hydrogen absorption at or near the systemic velocities of their host galaxies. Models proposed to explain this phenomenon involve a circumnuclear torus of gas and dust. The orientation of this structure determines whether or not the central engine appears obscured. Understanding the spatial distribution and kinematics of the HI detected toward the central parsecs of these sources...
Source: http://arxiv.org/abs/astro-ph/0009371v1
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Sep 22, 2013
09/13
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M. Giroletti; G. Giovannini; G. B. Taylor; R. Falomo
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eye 66
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We present a radio/optical study of a sample of BL Lac objects at arcsecond and milliarcsecond resolution. The sample consists of 30 nearby (z
Source: http://arxiv.org/abs/astro-ph/0309380v1
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Sep 23, 2013
09/13
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G. Giovannini; E. Liuzzo; M. Giroletti; G. B. Taylor
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eye 51
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We present an update of the parsec scale properties of the Bologna Complete Sample consisting of 95 radio sources from the B2 Catalog of Radio Sources and the Third Cambridge Revised Catalog (3CR), with z < 0.1. Thanks to recent new data we have now parsec scale images for 76 sources of the sample. Most of them show a one-sided jet structure but we find a higher fraction of two-sided sources in comparison with previous flux-limited VLBI surveys. A few peculiar sources are presented and...
Source: http://arxiv.org/abs/0810.0143v1
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Sep 23, 2013
09/13
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G. B. Taylor; A. C. Fabian; S. W. Allen
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We present multi-frequency VLA observations of the radio galaxy PKS 1246-410 at the center of the Centaurus Cluster, and compare these results to recent Chandra observations. The unusual radio morphology of PKS 1246-410 probably results from interactions with the hot, X-ray emitting gas. This gas, along with cluster magnetic fields, also produces substantial Faraday Rotation Measures towards PKS 1246-410. We discuss these observations in the context of a sample of 14 luminous X-ray clusters...
Source: http://arxiv.org/abs/astro-ph/0109337v1
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Sep 21, 2013
09/13
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E. Liuzzo; G. B. Taylor; G. Giovannini; M. Giroletti
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The aim of the present work is to study the radio emission on the parsec scale of 4C 26.42, the Brightest cluster galaxy in Abell 1795, in the framework of radiosources in a dense cool core cluster. We present Very Long Baseline Array (VLBA) observations at 1.6, 5, 8.4 and 22 GHz. We performed a spectral index and multiepoch analysis. The source appears two-sided with a well defined and symmetric Z-structure at ~5 mas from the core. The kiloparsec-scale morphology is similar to the parsec-scale...
Source: http://arxiv.org/abs/0905.3453v1
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Jul 20, 2013
07/13
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J. S. Sanders; A. C. Fabian; G. B. Taylor
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eye 104
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We present results from an observation of the luminous cluster of galaxies Abell 2204 using the Chandra X-ray Observatory. We show the core of the cluster has a complex morphological structure, made up of a high density core (n_e~0.2 cm^-3) with flat surface brightness, a surrounding central plateau, a tail-like feature, wrapping around to the east, and an unusual radio source. A temperature map and deprojected-profile shows that the temperature rises steeply outside these regions, until around...
Source: http://arxiv.org/abs/astro-ph/0406094v1
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Sep 18, 2013
09/13
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Y. M. Pihlström; G. B. Taylor; J. Granot; S. Doeleman
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eye 52
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We present high sensitivity Very Long Baseline Interferometry (VLBI) observations 806 days after the gamma-ray burst of 2003 March 29 (GRB030329). The angular diameter of the radio afterglow is measured to be 0.347 +- 0.09 mas, corresponding to 0.99 +- 0.26 pc at the redshift of GRB030329 (z = 0.1685). The evolution of the image size favors a uniform external density over an R^-2 wind-like density profile (at distances of R >~10^18 cm from the source), although the latter cannot be ruled out...
Source: http://arxiv.org/abs/0704.2085v1
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Sep 23, 2013
09/13
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R. J. H. Dunn; A. C. Fabian; G. B. Taylor
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We extend our earlier work on cluster cores with distinct radio bubbles, adding more active bubbles, i.e. those with Ghz radio emission, to our sample, and also investigating ``ghost bubbles,'' i.e. those without GHz radio emission. We have determined k, which is the ratio of the total particle energy to that of the electrons radiating between 10 MHz and 10 GHz. Constraints on the ages of the active bubbles confirm that the ratio of the energy factor, k, to the volume filling factor, f lies...
Source: http://arxiv.org/abs/astro-ph/0510191v1
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Sep 23, 2013
09/13
by
G. B. Taylor; P. Charlot; R. C. Vermeulen; N. Pradel
texts
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We report on a multi-frequency, multi-epoch campaign of Very Long Baseline Interferometry observations of the radio galaxy 1946+708 using the VLBA and a Global VLBI array. From these high-resolution observations we deduce the kinematic age of the radio source to be $\sim$4000 years, comparable with the ages of other Compact Symmetric Objects (CSOs). Ejections of pairs of jet components appears to take place on time scales of 10 years and these components in the jet travel outward at intrinsic...
Source: http://arxiv.org/abs/0904.1879v1
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70
Sep 20, 2013
09/13
by
T. A. Ensslin; C. Vogt; T. E. Clarke; G. B. Taylor
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We investigate the origin of the high Faraday rotation measures (RMs) found for polarized radio galaxies in clusters. The two most likely origins are, magnetic fields local to the source, or magnetic fields located in the foreground intra-cluster medium (ICM). The latter is identified as the null hypothesis. Rudnick & Blundell (2003) have recently suggested that the presence of magnetic fields local to the source may be revealed in correlations of the position angles (PAs) of the source...
Source: http://arxiv.org/abs/astro-ph/0301552v4
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71
Sep 20, 2013
09/13
by
R. J. Beswick; A. B. Peck; G. B. Taylor; G. Giovannini
texts
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Using a combination of observations involving the VLA, MERLIN and global VLBI networks we have made a detailed study of the radio continuum and the neutral hydrogen (HI) kinematics and distribution within the central kiloparsec of the radio galaxy 3C293. These observations trace the complex jet structure and identify the position of the steeply inverted radio core at 1.3GHz. Strong HI absorption is detected against the majority of the inner kiloparsec of 3C293. This absorption is separated into...
Source: http://arxiv.org/abs/astro-ph/0404295v1
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76
Sep 24, 2013
09/13
by
N. E. Gugliucci; G. B. Taylor; A. B. Peck; M. Giroletti
texts
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We present multi-epoch VLBA observations of Compact Symmetric Objects (CSOs) from the COINS sample (CSOs Observed In the Northern Sky). These observations allow us to make estimates of, or place limits on, the kinematic ages for those sources with well-identified hot spots. This study significantly increases the number of CSOs with well-determined ages or limits. The age distribution is found to be sharply peaked under 500 years, suggesting that many CSOs die young, or are episodic in nature,...
Source: http://arxiv.org/abs/astro-ph/0412199v1
