237 research outputs found
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
Do the mildly superluminal VLBI knots exclude ultrarelativistic blazar jets?
We compute the effective values of apparent transverse velocity and flux
boosting factors for the VLBI radio knots of blazar jets, by integrating over
the angular distributions of these quantities across the widths of jets with
finite opening angles but constant velocities. For high bulk Lorentz factors
(Gamma > 10) variations across the jet can be quite large if the opening angle,
omega, is even a few degrees on sub-parsec scales. The resulting apparent
speeds are often much lower than those obtained from the usual analyses that
ignore the finite jet opening angles. We can thus reconcile the usually
observed subluminal or mildly superluminal speeds with the very high (>~ 20)
Gamma factors, required by the inverse Compton origin and rapid variability of
TeV fluxes, as well as by intraday radio variability. Thus it is possible to
associate the VLBI radio knots directly with shocks in the ultra-relativistic
main jet flow, without invoking very rapid jet deceleration on parsec scales,
or extremely unlikely viewing angles.Comment: 10 pages, 1 figure, to appear in ApJ Letters, Nov. 10 2004 issu
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
What do HST and Chandra tell us about the jet and the nuclear region of the radio galaxy 3C270?
The HST/STIS ultraviolet image of the FR I radio galaxy 3C270 shows the
presence of a jet-like structure emerging from the position of the nucleus.
This feature, which represents the first jet-like component ever detected in
the UV in a radio galaxy with jets lying almost on the plane of the sky, has
the same position angle as the jet in the radio and X-ray images. We propose
two different scenarios for the origin of the emission: i) non-thermal
synchrotron from a mildly relativistic component of the jet; ii) scattered
light from the nucleus, where a BL Lac source may be hosted. Either of these
pictures would have important consequences for the AGN unification schemes and
for our knowledge of the jet structure. In the Chandra image a faint
counter-jet is also present. From a comparative analysis of the HST images and
Chandra X-ray spectrum, we find that the nucleus is only moderately obscured.
The obscuring structure might well reside in the geometrically thin dark disk
observed on large scales. This fits the scenario in which a standard
geometrically and optically thick torus is not present in FR I radio galaxies.Comment: 13 pages, 5 figures, in press on ApJ. Revised version, the discussion
has been improved according to the requests of the refere
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 networ
WFPC2 LRF Imaging of Emission Line Nebulae in 3CR Radio Galaxies
We present HST/WFPC2 Linear Ramp Filter images of high surface brightness
emission lines (either [OII], [OIII], or H-alpha+[NII]) in 80 3CR radio
sources. We overlay the emission line images on high resolution VLA radio
images (eight of which are new reductions of archival data) in order to examine
the spatial relationship between the optical and radio emission. We confirm
that the radio and optical emission line structures are consistent with weak
alignment at low redshift (z < 0.6) except in the Compact Steep Spectrum (CSS)
radio galaxies where both the radio source and the emission line nebulae are on
galactic scales and strong alignment is seen at all redshifts. There are weak
trends for the aligned emission line nebulae to be more luminous, and for the
emission line nebula size to increase with redshift and/or radio power. The
combination of these results suggests that there is a limited but real capacity
for the radio source to influence the properties of the emission line nebulae
at these low redshifts (z < 0.6). Our results are consistent with previous
suggestions that both mechanical and radiant energy are responsible for
generating alignment between the radio source and emission line gas.Comment: 80 pages, 54 figures. Accepted for publication in ApJ
High Energy gamma-rays From FR I Jets
Thanks to Hubble and Chandra telescopes, some of the large scale jets in
extragalactic radio sources are now being observed at optical and X-ray
frequencies. For the FR I objects the synchrotron nature of this emission is
surely established, although a lot of uncertainties - connected for example
with the particle acceleration processes involved - remain. In this paper we
study production of high energy gamma-rays in FR I kiloparsec-scale jets by
inverse-Compton emission of the synchrotron-emitting electrons. We consider
different origin of seed photons contributing to the inverse-Compton
scattering, including nuclear jet radiation as well as ambient, stellar and
circumstellar emission of the host galaxies. We discuss how future detections
or non-detections of the evaluated gamma-ray fluxes can provide constraints on
the unknown large scale jet parameters, i.e. the magnetic field intensity and
the jet Doppler factor. For the nearby sources Centaurus A and M 87, we find
measurable fluxes of TeV photons resulting from synchrotron self-Compton
process and from comptonisation of the galactic photon fields, respectively. In
the case of Centaurus A, we also find a relatively strong emission component
due to comptonisation of the nuclear blazar photons, which could be easily
observed by GLAST at energy ~10 GeV, providing important test for the
unification of FR I sources with BL Lac objects.Comment: 39 pages, 6 figures included. Modified version, accepted for
publication in Astrophysical Journa
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