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Daniel A. Evans
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We present results from a new 100-ks Suzaku observation of the nearby radio galaxy 3C 33, and investigate the nature of absorption, reflection, and jet production in this source. We model the 2-70 keV nuclear continuum with a power law that is absorbed either through one or more layers of pc-scale neutral material, or through a modestly ionized pc-scale obscurer. The expected signatures of reflection from a neutral accretion disk are absent in 3C 33: there is no evidence of a relativistically blurred Fe K$alpha$ emission line, and no Compton reflection hump above 10 keV. We discuss the implications of this for the nature of jet production in 3C 33.
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We present multi-frequency radio observations with the Giant Metrewave Radio Telescope and Very Large Array, and X-ray observations with the X-ray Multi-Mirror Mission ({it XMM-Newton}) telescope of the giant radio source (GRS) 3C 457. We have detected the core, lobes and the environment of the GRS in X-ray. We examine the relationships between the radio and X-ray emission, determine the radio spectrum over a large frequency range and attribute the X-ray emission from the lobes to the inverse-Compton scattering of cosmic microwave background (CMB) photons. The magnetic field strength of the lobes is very close to the equipartition value. Both the lobes are in pressure balance near the hotspots and apparently under-pressured towards the core. The X-ray spectrum of the core of the GRS consists of an unabsorbed soft power-law component and a heavily absorbed hard power-law component. The soft unabsorbed component is likely to be related to the radio jets. There is no strong evidence of Fe K$alpha$ emission line in our data.
We present optical integral field spectroscopy $-$ obtained with the Gemini Multi-Object Spectrograph $-$ of the inner $4.0 times 5.8$ kpc$^2$ of the narrow line radio galaxy 3C 33 at a spatial resolution of 0.58 kpc. The gas emission shows three brightest structures: a strong knot of nuclear emission and two other knots at $approx 1.4$ kpc south-west and north-east of the nucleus along the ionization axis. We detect two kinematic components in the emission lines profiles, with a broader component (with velocity dispersion $sigma > 150$ km s$^{-1}$) being dominant within a $sim$ 1 kpc wide strip (the nuclear strip) running from the south-east to the north-west, perpendicular to the radio jet, and a narrower component ($sigma < 100$ km s$^{-1}$) dominating elsewhere. Centroid velocity maps reveal a rotation pattern with velocity amplitudes reaching $sim pm 350$ km s$^{-1}$ in the region dominated by the narrow component, while residual blueshifts and redshifts relative to rotation are observed in the nuclear strip, where we also observe the highest values of the [N II]/H{alpha}, [S II]/H{alpha} and [O I]/H{alpha} line ratios, and an increase of the gas temperature ($sim 18000$ K), velocity dispersion and electron density ($sim 500$ cm$^{-3}$). We interpret these residuals and increased line ratios as due to a lateral expansion of the ambient gas in the nuclear strip due to shocks produced by the passage of the radio jet. The effect of this expansion in the surrounding medium is very small, as its estimated kinetic power represents only $2.6 - 3.0 times 10^{-5}$ of the AGN bolometric luminosity. A possible signature of inflow is revealed by an increase in the [O I]/H{alpha} ratio values and velocity dispersions in the shape of two spiral arms extending to 2.3 kpc north-east and south-west from the nucleus.
We report the results of monitoring of the radio galaxy 3C 120 with the Neil Gehrels Swift Observatory, Very Long Baseline Array, and Metsahovi Radio Observatory. The UV-optical continuum spectrum and R-band polarization can be explained by a superposition of an inverted-spectrum source with a synchrotron component containing a disordered magnetic field. The UV-optical and X-ray light curves include dips and flares, while several superluminal knots appear in the parsec-scale jet. The recovery time of the second dip was longer at UV-optical wavelengths, in conflict with a model in which the inner accretion disk (AD) is disrupted during a dip and then refilled from outer to inner radii. We favor an alternative scenario in which occasional polar alignments of the magnetic field in the disk and corona cause the flux dips and formation of shocks in the jet. Similar to observations of Seyfert galaxies, intra-band time lags of flux variations are longer than predicted by the standard AD model. This suggests that scattering or some other reprocessing occurs. The 37 GHz light curve is well correlated with the optical-UV variations, with a ~20-day delay. A radio flare in the jet occurred in a superluminal knot 0.14 milliarcseconds downstream of the 43 GHz core, which places the site of the preceding X-ray/UV/optical flare within the core 0.5-1.3 pc from the black hole. The inverted UV-optical flare spectrum can be explained by a nearly mono-energetic electron distribution with energy similar to the minimum energy inferred in the TeV gamma-ray emitting regions of some BL Lacertae objects.
Centaurus B is a nearby radio galaxy positioned in the Southern hemisphere close to the Galactic plane. Here we present a detailed analysis of about 43 months of accumulated Fermi-LAT data of the gamma-ray counterpart of the source initially reported in the 2nd Fermi-LAT catalog, and of newly acquired Suzaku X-ray data. We confirm its detection at GeV photon energies, and analyze the extension and variability of the gamma-ray source in the LAT dataset, in which it appears as a steady gamma-ray emitter. The X-ray core of Centaurus B is detected as a bright source of a continuum radiation. We do not detect however any diffuse X-ray emission from the known radio lobes, with the provided upper limit only marginally consistent with the previously claimed ASCA flux. Two scenarios that connect the X-ray and gamma-ray properties are considered. In the first one, we assume that the diffuse non-thermal X-ray emission component is not significantly below the derived Suzaku upper limit. In this case, modeling the inverse-Compton emission shows that the observed gamma-ray flux of the source may in principle be produced within the lobes. This association would imply that efficient in-situ acceleration of the radiating electrons is occurring and that the lobes are dominated by the pressure from the relativistic particles. In the second scenario, with the diffuse X-ray emission well below the Suzaku upper limits, the lobes in the system are instead dominated by the magnetic pressure. In this case, the observed gamma-ray flux is not likely to be produced within the lobes, but instead within the nuclear parts of the jet. By means of synchrotron self-Compton modeling we show that this possibility could be consistent with the broad-band data collected for the unresolved core of Centaurus B, including the newly derived Suzaku spectrum.
We present the results of deep 140 ks Suzaku X-ray observations of the north-east (NE) radio relic of the merging galaxy cluster Abell2255. The temperature structure of Abell2255 is measured out to 0.9 times the virial radius (1.9 Mpc) in the NE direction for the first time. The Suzaku temperature map of the central region suggests a complex temperature distribution, which agrees with previous work. Additionally, on a larger-scale, we confirm that the temperature drops from 6 keV around the cluster center to 3 keV at the outskirts, with two discontinuities at {it r}$sim$5arcmin~(450 kpc) and $sim$12arcmin~(1100 kpc) from the cluster center. Their locations coincide with surface brightness discontinuities marginally detected in the XMM-Newton image, which indicates the presence of shock structures. From the temperature drop, we estimate the Mach numbers to be ${cal M}_{rm inner}sim$1.2 and, ${cal M}_{rm outer}sim$1.4. The first structure is most likely related to the large cluster core region ($sim$350--430 kpc), and its Mach number is consistent with the XMM-Newton observation (${cal M}sim$1.24: Sakelliou & Ponman 2006). Our detection of the second temperature jump, based on the Suzaku key project observation, shows the presence of a shock structure across the NE radio relic. This indicates a connection between the shock structure and the relativistic electrons that generate radio emission. Across the NE radio relic, however, we find a significantly lower temperature ratio ($T_1/T_2sim1.44pm0.16$ corresponds to~${cal M}_{rm X-ray}sim1.4$) than the value expected from radio wavelengths, based on the standard diffusive shock acceleration mechanism ($T_1/T_2>$ 3.2 or ${cal M}_{rm Radio}>$ 2.8).
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