Lobe Emission Research Articles

Aperture Synthesis Observations of Cygnus A at 86.2 Ghz

Recent observations of Cygnus A with the Hat Creek interferometer at 86.2 GHz limit the spectral curvature of the hotspots and show that the diffuse lobe emission has a spectral index of about 1.5. The central component is, at most, weakly variable and its spectrum shows a distinct break to a spectral index near 0.65 at about 20 GHz.

Is a bi-stable beam responsible for the complex radio structure of 3C133?

It is generally assumed that the extended lobes of radio emission found in many extragalactic sources are powered by oppositely directed supply beams of relativistic particles emanating from the central galactic nucleus1,2. The complexity and asymmetry of the structure in many sources has, however, led to speculation of a ‘flip-flop’ beam mechanism3,4 where energy is supplied alternately to each radio lobe. Recent high resolution observations of the radio structure of 3C133 reveal a complex structure in which rotation of the source axis may have uncovered evidence for such a bi-stable nature of the energy supply. There are, however, several difficulties in such an interpretation.

The quasar 3C351 - VLA maps and a deep search for optical emission in the outer lobes

view Abstract Citations (10) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The quasar 3C 351: VLA maps and a deep search for optical emission in the outer lobes. Kronberg, P. P. ; Clarke, J. N. ; van den Bergh, S. Abstract VLA radio maps of the quasar 3C35 1 (z = 0.371) at ∼2" and 0."4 resolution (a) show interaction with a relatively dense intergalactic medium, (b) show that there is electron acceleration within at least one of the radio lobes, and (c) imply that the intergalactic gas density is different on one side of the source than on the other. Striking similarities are found between the northern radio lobe of 3C351 and one of the outer hotspots of Cygnus A, and possibly other similar systems, in that the outer, on-axis hotspot is resolved and cusp-shaped, and the "secondary" off-axis hotspot is more compact. A search for optical emission in the outer lobes shows no emission stronger than 22m in the J band and ∼21m in the F band. There is also no evidence at these limits for a cluster of galaxies near the radio source, as is suggested by our conclusion that it is interacting with a medium of typical intracluster density. Publication: The Astronomical Journal Pub Date: August 1980 DOI: 10.1086/112760 Bibcode: 1980AJ.....85..973K Keywords: Astronomical Maps; Light Emission; Quasars; Radio Astronomy; Electron Acceleration; Intergalactic Media; Visual Observation; Astrophysics full text sources ADS | data products SIMBAD (1) NED (1)

Superradiance triggering spectroscopy

The injection of a weak resonant field on a superradiant sample can induce large changes in the delay and spatial pattern of the emission. By measuring the change in direction of the emission lobes as a function of the injection field frequency, we have recorded the spectrum of the 7P 3 2 − 7S 1 2 superradiant transition in cesium. As expected from theory, only a few photons per pulse are needed to record the spectrum. Various applications to very sensitive spectroscopy and to amplifier technology are discussed.

Suppression of side lobes in the far field of AlGaAs DH stripe lasers by a Te facet coating

Side lobes observed in the far-field distribution parallel to the junction plane of DH AlGaAs stripe-geometry lasers can be suppressed by a self-aligned facet masking process. A hole, burnt into a Te coating by the laser emission, allows only the main lobe emission to pass. The result supports the attribution of side lobes to refraction tails in the near field typical of a negative refractive index step wave guide as discussed in a previous paper [see R. W. Engelmann, D. Kerps, and F. Nunes, IEEE Quantum Electron. (to be published)].

Optical emission in the radio lobes of radio galaxies

We have found photographic and photometric evidence for optical emission in the radio lobes of 3C 285, 3C 265, and 3C 390.3. The optical luminosity of this emission lies between Bapprox.26 and Bapprox.22 mag arcsec/sup -2/. We discuss possible mechanisms of optical emission and their implications for models of radio galaxies. If the optical radiation arises from inverse Compton scattering of the blackbody background radiation, it provides a fairly direct method for measuring the magnetic fields in radio galaxies. For simple models, such fields would be below the equipartition value. If, on the other hand, the optical radiation is the visible extension of the radio synchrotron, it sets strong limits on the lifetimes of the relativistic electrons which must be regenerated in the extended source. We have examined several of the emission regions for optical polarization in order to help distinguish among these possiblities. These are all the radio galaxies which we have examined at the time of writing.

Chemisorption-Induced Surface Umklapp Processes in Angle-Resolved Synchrotron Photoemission from W(001)

Angle-resolved photoemission, using synchrotron radiation, from the chemisorption system W(001) + H shows a very large doublet of peaks at initial energies -1.3 and -0.6 eV for quarter-monolayer coverage which disappear at higher coverage. The emission lobes are strongly peaked in the $〈110〉$ azimuths and are attributed to essentially pure bulk W transitions. The electrons are emitted in the new directions through the influence of "extra" surface reciprocal lattice vectors associated with the hydrogen $c(2\ifmmode\times\else\texttimes\fi{}2)$ superstructure.

Potential of Field Emission Cathodes for Microfabrication

For field-emitter tip currents in the range of 100 μA, field-emission guns can compete favorably with thermionic LaB6 guns for microfabrication with 2000 Å working beam diameters. The stable operation of tip currents between 10 and 1000 μA, for periods totalling hundreds of hours, requires an understanding of the steady-state and transient adsorbed gas layer on the emitter surface. This has been accomplished in a simple gun-lens. Furthermore, Boersch effect energy broadening appears to be significantly operative at emission intensities on the order of 10−2 A/sr. The staircase-like current fluctuations indicate quantum events on the emitter surface. In fact, intense emission lobes have been spatially separated by spherical aberration in a large aperture configuration.