A sample of low-redshift BL Lacertae objects. II. EVN and MERLIN data and multi-wavelength analysis

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 sample from which the subset with new radio data is drawn. We derive Doppler factors in the parsec scale radio jet in the range ~2 < delta < ~9. Using HST data, we separate the contribution of the host galaxy from that of the active core. From the measured and de-beamed observables, we find a weak correlation between radio power and black hole mass, and a tight correlation between radio and optical core luminosities. We interpret this result in terms of a common synchrotron origin, with little contribution from a radiatively efficient accretion disk. The BL Lacs in our sample have de-beamed properties similar to low power radio galaxies, including the fundamental plane of black hole activity.Comment: Accepted by ApJ. 17 page

870 micron observations of nearby 3CRR radio galaxies

We present submillimeter continuum observations at 870 microns of the cores of low redshift 3CRR radio galaxies, observed at the Heinrich Hertz Submillimeter Telescope. The cores are nearly flat spectrum between the radio and submillimeter which implies that the submillimeter continuum is likely to be synchrotron emission and not thermal emission from dust. The emitted power from nuclei detected at optical wavelengths and in the X-rays is similar in the submillimeter, optical and X-rays. The submillimeter to optical and X-ray power ratios suggest that most of these sources resemble misdirected BL Lac type objects with synchrotron emission peaking at low energies. However we find three exceptions, the FR I galaxy 3C264 and the FR II galaxies 3C390.3 and 3C338 with high X-ray to submillimeter luminosity ratios. These three objects are candidate high or intermediate energy peaked BL Lac type objects. With additional infrared observations and from archival data, we compile spectral energy distributions (SEDs) for a subset of these objects. The steep dips observed near the optical wavelengths in many of these objects suggest that extinction inhibits the detection and reduces the flux of optical continuum core counterparts. High resolution near or mid-infrared imaging may provide better measurements of the underlying synchrotron emission peak.Comment: accepted for publication in A

Photon breeding mechanism in relativistic jets: astrophysical implications

Photon breeding in relativistic jets involves multiplication of high-energy photons propagating from the jet to the external environment and back with the conversion into electron-positron pairs. The exponential growth of the energy density of these photons is a super-critical process powered by the bulk energy of the jet. The efficient deceleration of the jet outer layers creates a structured jet morphology with the fast spine and slow sheath. In initially fast and high-power jets even the spine can be decelerated efficiently leading to very high radiative efficiencies of conversion of the jet bulk energy into radiation. The decelerating, structured jets have angular distribution of radiation significantly broader than that predicted by a simple blob model with a constant Lorentz factor. This reconciles the discrepancy between the high Doppler factors determined by the fits to the spectra of TeV blazars and the low apparent velocities observed at VLBI scales as well as the low jet Lorentz factors required by the observed statistics and luminosity ratio of Fanaroff-Riley I radio galaxies and BL Lac objects. Photon breeding produces a population of high-energy leptons in agreement with the constraints on the electron injection function required by spectral fits of the TeV blazars. Relativistic pairs created outside the jet and emitting gamma-rays by inverse Compton process might explain the relatively high level of the TeV emission from the misaligned jet in the radio galaxies. The mechanism reproduces basic spectral features observed in blazars including the blazar sequence (shift of the spectral peaks towards lower energies with increasing luminosity). The mechanism is very robust and can operate in various environments characterised by the high photon density.Comment: 6 pages, 3 figures, to appear in the proceedings of the HEPRO conference, September 24-28, 2007, Dublin, Irelan

The Parsec-Scale Jets of the TeV Blazars H 1426+428, 1ES 1959+650, and PKS 2155-304: 2001-2004

We present Very Long Baseline Array (VLBA) observations of the TeV blazars H 1426+428, 1ES 1959+650, and PKS 2155-304 obtained during the years 2001 through 2004. We observed H 1426+428 at four epochs at 8 GHz, and found that its parsec-scale structure consisted of a ~17 mJy core and a single ~3 mJy jet component with an apparent speed of 2.09 +/- 0.53c. The blazar 1ES 1959+650 was observed at three epochs at frequencies of 15 and 22 GHz. Spectral index information from these dual-frequency observations was used to definitively identify the core of the parsec-scale structure. PKS 2155-304 was observed at a single epoch at 15 GHz with dual-circular polarization, and we present the first VLBI polarimetry image of this source. For 1ES 1959+650 and PKS 2155-304, the current observations are combined with the VLBA observations from our earlier paper to yield improved apparent speed measurements for these sources with greatly reduced measurement errors. The new apparent speed measured for component C2 in 1ES 1959+650 is 0.00 +/- 0.04c (stationary), and the new apparent speed measured for component C1 in PKS 2155-304 is 0.93 +/- 0.31c. We combine the new apparent speed measurements from this paper with the apparent speeds measured in TeV blazar jets from our earlier papers to form a current set of apparent speed measurements in TeV HBLs. The mean peak apparent pattern speed in the jets of the TeV HBLs is about 1c. We conclude the paper with a detailed discussion of the interpretation of the collected VLBA data on TeV blazars in the context of current theoretical models for the parsec-scale structure of TeV blazar jets.Comment: 16 pages, Astrophysical Journal, in pres

Plastic optical fiber network for electronic control unit and power electronics in by-wire vehicles

Innovative connection between ECUs and power electronics realized with POF (Plastic Optic Fiber) is designed. The POF connection allows to increase the bandwidth, the electromagnetic immunity, galvanic insulation and the fault tolerance. Considering automotive ECUs nets the POF network can be used to realize a safe network

The AGN Obscuring Torus -- End of the "Doughnut" Paradigm?

Unified schemes of active galactic nuclei (AGN) require an obscuring dusty torus around the central engine. The compact sizes (only a few pc) determined in recent high-resolution observations require that the obscuring matter be clumpy and located inside the region where the black-hole gravity dominates over the galactic bulge. This location is in line with the scenario depicting the torus as the region of the clumpy wind coming off the accretion disk in which the clouds are dusty and optically thick. We study here the outflow scenario within the framework of hydromagnetic disk winds, incorporating the cloud properties determined from detailed modeling of the IR emission from clumpy tori. We find that torus clouds were likely detected in recent water maser observations of NGC 3079. In the wind scenario, the AGN main dynamic channel for release of accreted mass seems to be switching at low luminosities from torus outflow to radio jets. The torus disappears when the bolometric luminosity decreases below about \E{42} erg/sec because the accretion onto the central black hole can no longer sustain the required cloud outflow rate. This disappearance seems to have been observed in both LINERs and radio galaxies. With further luminosity decrease, suppression of cloud outflow spreads radially inward from the disk's dusty, molecular region into its atomic, ionized zone, resulting in disappearance of the broad emission line region at lower luminosities, yet to be determined.Comment: ApJ Letters, to be publishe