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Axon, D. J.

Publications and source records attributed to Axon, D. J..

6 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

HST/FOC imaging of the narrow-line region of NGC 1068

We present imaging observations of NGC 1068 taken with the COSTAR-corrected (Corrective-Optics Space Telescope Axial Replacement) Faint Object Camera (FOC) on board the Hubble Space Telescope (HST) in the UV and optical continuum and (O III) emission lines. From these observations the structure of the nuclear region of NGC 1068 is shown to be very complex. Bright filamentary and patchy structures are intermingled with dark lanes. Other interesting features are identified, including the location of the UV peak with respect to the peak of line emission, the existence of an unusual 'twin-crescent' object near the nucleus, and point sources in the field. In the UV to optical flux ratio image, an extended conical region stands out for its blue color which may be tracing reflected nuclear light.

Macchetto, F.↗
NASA NTRS1991

Molecular hydrogen polarization images of OMC-1

An image of the polarization of the shocked H2 v = 1-0 S(1) line emission in the core of OMC-1 has been obtained. Along the molecular outflow of the source, the line is dichroically polarized by a medium of aligned grains located between the earth and the shock fronts. The polarization pattern traces the magnetic field direction, which is parallel to the outflow axis and to the large-scale field direction determined from far-IR continuum measurements. Close to the IR source IRc2, the likely source of the outflow, the aligned vectors twist, indicating that the magnetic field direction changes. Modeling the line ratios of scattered H2 lines in the reflection nebula, it is concluded that the size distribution of grains there is typical of the small grains in the diffuse interstellar medium. By contrast, the scattered continuum radiation from the core region suggests that the grains there are larger than this.

Burton, Michael G.↗
NASA NTRS1990

The morphology of Sersic-Pastoriza galaxies

The authors present the preliminary results of their radio-continuum and neutral hydrogen observations of Sersic-Pastoriza (S-P) galaxies. They show that the central regions contain a population of compact features thought to be young supernova remnants (SNRs) and discuss the overall morphology of the nuclei.

Yates, G. J.↗
NASA NTRS1987

Models relating the radio emission and ionised gas in Seyfert nuclei

Possible models are discussed in which the radio emitting components in Seyfert II nuclei can compress and accelerate the ambient nuclear medium to produce the characteristics of the narrow line region. A first order model, which considers only the expansion of the radio components, is briefly described. However, in many Seyfert nuclei it appears that the linear motion of the radio components is also important. This can result in shock heating of the ambient medium, and if the cooling time is long enough, can lead to a displacement between the radio component and the associated emission lines. This effect may be present in NGC 1068 and NGC 5929 and by considering ram pressure balance and the cooling length it is possible to estimate lobe velocities and ambient densities.

Pedlar, A.↗
NASA NTRS1982

The noise of BL Lacertae

Results are presented from an intensive optical and IR monitoring program of the flux and polarization characteristics of BL Lac. It is found that the polarization variations increase in amplitude with increasing time interval, and that the path traced out by the polarization vector in the Q-U plane is a random walk. In view of earlier measurements of BL Lac, the polarization fluctuations can be represented at low frequencies by the flat power spectrum of white noise, up to a frequency of 0.05 cycles/day. Above this frequency, the spectrum steepens to that of a random walk. A model for BL Lac suggested by the polarimetric noise can be constructed from independent sources of light with randomly oriented, strong polarization. Small random differences in spectral index from source to source could also explain the variable wavelength dependence of polarization.

Moore, R. L.↗