VLBI Observations of a Complete Sample of Radio Galaxies V. 3C346 and 4C31.04: two Unusual CSS Sources

We present observations at 1.7 and 8.4 GHz of two Compact Steep Spectrum (CSS) sources from a complete sample of low-intermediate power radio galaxies. 3C346 shows an asymmetric structure with a one-sided ``jet'' and ``hot spot''. Present observations suggest that the classification of this source as a CSS is inappropriate, and that it is a common radio galaxy at a small angle to the line of sight. Its properties are in agreement with the predictions of unified schemes models. 4C31.04 shows more complex structure with the possibility of a centrally located flat spectrum core in between two close lobes. We suggest that this source could be a low redshift Compact Symmetric Object.Comment: 15 pages, LATEX, uuenconde ps figures To be published in the Astrophysical Journal, October 20th issu

Effects of muscle fatigue on gait characteristics under single and dual-task conditions in young and older adults

Muscle fatigue and dual-task walking (e.g., concurrent performance of a cognitive interference (CI) while walking) represent major fall risk factors in young and older adults. Thus, the objectives of this study were to examine the effects of muscle fatigue on gait characteristics under single and dual-task conditions in young and older adults and to determine the impact of muscle fatigue on dual-task costs while walking

Age-related effects on postural control under multi-task conditions

Changes in postural sway and gait patterns due to simultaneously performed cognitive (CI) and/or motor interference (MI) tasks have previously been reported and are associated with an increased risk of falling in older adults

Time dependent gamma-ray production in the anisotropic IC e±e^\pm pair cascade initiated by electrons in active galaxies

New high energy emission features have been recently discovered by the Cherenkov telescopes from active galaxies e.g., a few minutes variability time scale of TeV emission from Mrk 501 and PKS 2155-304, sub-TeV $\gamma$-ray emission from GeV peaked blazar 3C 279, and TeV emission from two nearby active galaxies, M87 and Cen A, which jets are inclined at a relatively large angle to the line of sight. These results have put a new light on the high energy processes occurring in central parts of active galaxies stimulating more detailed studies of $\gamma$-ray emission models. Here we report the results of a detailed analysis concerning the most general version of the model for the $\gamma$-ray production by leptons injected in the jet which interact with the thermal radiation from an accretion disk (the so called {\it external inverse Compton model}). We investigate the $\gamma$-ray spectra produced in an anisotropic Inverse Compton (IC) $e^\pm$ pair cascade in the whole volume above the accretion disk. The cascade $\gamma$-ray spectra are obtained for different locations of the observer in respect to the direction of the jet. We also study the time evolution of this $\gamma$-ray emission caused by the propagation of the relativistic leptons along the jet and the delays resulting from different places of the origin of $\gamma$-rays above the accretion disk. We discuss the main features of such a cascade model assuming constant injection rate of electrons along the jet. We are investigating two models for their different maximum energies: constant value independent on the distance along the jet or limited by the synchrotron energy losses considered locally in the jet. The model is discussed in the context of blazars observed at small and large inclination angles taking as an example the parameters of the two famous sources Cen A and 3C 279.Comment: 16 pages, 18 figures, accepted for publication in MNRA

Relation between millimeter wavelengths emission and high-energy emission for active galactic nuclei

After comparing the flux densities of a sample of active galactic nuclei detected by energetic gamma-ray experiment telescope at 90 and 230 GHz with the $\gamma$-ray emissions detected by Compton Gamma Ray Observatory and x-ray emission, a strong correlation between the emissions at the millimeter wavelength and the $\gamma$-ray emission is found. The average flux density of x-ray is almost proportional to the average flux density at the millimeter wavelength for quasars detected by energetic gamma-ray experiment telescope, which strongly supports the previous idea that the x-ray emissions of this kind sources are mainly produced by Synchrotron Self-Compton process.Comment: 6 pages, Chinese Physics Letters in pres

VLBI Observations of a Complete Sample of Radio Galaxies. VI. The Two FR-I Radio Galaxies B2 0836+29 and 3C465

We present 5 GHz global VLBI observations of the two Fanaroff Riley Type I radio galaxies B2 0836+29 and 3C465 (2335+26). For 3C465 we present also 1.7 GHz and 8.4 GHz global VLBI data. In addition VLA observations were used to obtain arsecond resolution continuum and polarization maps at 5 GHz. Both sources are very asymmetric on the parsec-scale, with a core and a one-sided jet, aligned with the main arcsecond scale jet. We place a limit on the milliarcsecond jet to counterjet brightness ratio B$_{jet}$/B$_{cjet}$ \gtsim 20 and \gtsim 30 for B2 0836+29 and 3C465 respectively. For 3C465 the strong asymmetry holds to the kiloparsec scale. The brightness asymmetry and the ratio between the core radio power and total radio power allow us to constrain the jet velocity close to the core and the orientation of the radio structure with respect to the line of sight. The results suggest that the plasma speed is relativistic on the parsec scale for both sources, i.e. v$_{jet}$ \gtsim 0.75c for B2 0836+29 and v$_{jet}$ \gtsim 0.6c for 3C465. While v$_{jet}$ decreases from the parsec to the kiloparsec scale in B2 0836+29, in 3C465 the very high v$_{jet}$ holds all the way to the kiloparsec-scale {\t bright spot}. Our results are in agreement with the unification scheme suggestion that FR-I radio galaxies are the unbeamed poulation of BL-Lac objects. Furthermore, they reinforce the idea that the central engine in FR-I and FR-II radio galaxies must be qualitatively similar. The different radio morphology could then be due either to an intrinsically different nuclear power, which affects the torus geometry or to different conditions in the region beyond the parsec scale, where a significant deceleration in the FR-I jets occurs.Comment: 28 pages, 4 tables, 8 figures all available under request from [email protected]

XMM observations of the high-redshift quasar RXJ1028.6-0844 at z=4.276: soft X-ray spectral flattening

We present results from a new XMM-Newton observation of the high-redshift quasar RXJ1028.6-0844 at a redshift of 4.276. The soft X-ray spectral flattening, as reported by a study with ASCA previously (Yuan et al. 2000, ApJ 545, 625), is confirmed to be present, however, with reduced column density when modelled by absorption. The inferred column density for absorption intrinsic to the quasar is 2.1(+0.4-0.3)x10^22 (cm^-2) for cold matter, and higher for ionised gas. The spectral flattening shows remarkable similarity with those of two similar objects, GB1428+4217 (Worsley et al. 2004, MNRAS 350, L67) and PMNJ0525-3343 (Worsley et al. 2004, MNRAS 350, 207). The results improve upon those obtained from a previous short-exposure observation for RXJ1028.6-0844 with XMM-Newton (Grupe et al. 2004, AJ 127, 1). A comparative study of the two XMM-Newton observations reveals a change in the power-law photon index from Gamma ~1.3 to 1.5 on timescales of about one year. A tentative excess emission feature in the rest-frame 5-10keV band is suggested, which is similar to that marginally suggested for GB1428+4217.Comment: 9 pages, accepted for publication in MNRAS; minor changes (added footnote commenting on the use of the F-test, added references