Skip to main content Accessibility help
×
Home

3.7. Diffraction-limited IR speckle masking observations of the central regions of Seyfert galaxies

  • M. Wittkowski (a1) (a2), Y. Balega (a3), T. Beckert (a2), W.J. Duschl (a1) (a2), K.-H. Hofmann (a1) and G. Weigelt (a1)...

Extract

We present speckle masking observations of Seyfert galaxies with the Russian 6 m telescope. Diffraction-limited resolution of 76 mas in the K-band was obtained for the first time. This resolution is similar to the resolution of recent MERLIN and VLA observations of galactic centers, thus allowing us to study the radio-IR spectrum of the same structures. Figure 1 shows the decreasing K-band visibility function of NGC 1068 and the contour plot of our reconstructed image. The results show that NGC 1068 is resolved with a FWHM diameter of 30 mas or 2 pc for an assumed Gaussian flux distribution. The image is elongated in northern direction, which is approximately the direction of the radio jet. In the right panel of figure 1 the observed flux values at 5,15 and 22 GHz (from) are plotted together with our K-band flux. The spectral index between 5 GHz and the K-band is approximately 1/3. This spectrum can be explained by synchrotron emission of quasi-monoenergetic relativistic electrons (as for our Galactic Center by). Assuming that the observed flux is mainly nuclear light (from, for example, scattering lobes above and below a torus, without absorption and re-emission) we use the same synchrotron model as has been used for the Galactic Center to explain our data. With this model, we find a source radius of R ∼ 1015 cm, a magnetic field of B ∼ 11 G, a electron number density of ne ∼ 1.1103 cm−3 and a mean electron energy of ∼ 2.7 GeV. The corresponding model spectrum is shown in the right panel of fig. 1. The observed flux value at 2.2 μm lies slightly above the model spectrum. This could be caused by flux contributions from additional components, for example, a central stellar cluster, an accretion disk or thermal radiation from a dusty torus. We have also observed the central regions of other galaxies. For example, for NGC 4151, we found a dominant central core, which is not resolved, and therefore has a diameter of < 20 mas.

    • Send article to Kindle

      To send this article to your Kindle, first ensure no-reply@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about sending to your Kindle. Find out more about sending to your Kindle.

      Note you can select to send to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.

      Find out more about the Kindle Personal Document Service.

      3.7. Diffraction-limited IR speckle masking observations of the central regions of Seyfert galaxies
      Available formats
      ×

      Send article to Dropbox

      To send this article to your Dropbox account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your <service> account. Find out more about sending content to Dropbox.

      3.7. Diffraction-limited IR speckle masking observations of the central regions of Seyfert galaxies
      Available formats
      ×

      Send article to Google Drive

      To send this article to your Google Drive account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your <service> account. Find out more about sending content to Google Drive.

      3.7. Diffraction-limited IR speckle masking observations of the central regions of Seyfert galaxies
      Available formats
      ×

Copyright

References

Hide All
1. Beckert, T. et al., 1996, A&A 307, 450.
2. Lohmann, A.W. et al., 1983, Appl. Opt. 22, 4028.
3. Muxlow, T.W.B. et al., 1996, MNRAS 278, 854.
4. Weigelt, G.P. 1977, Opt Comm. 21, 55.
5. Wittkowski, M. et al., 1997, submitted.

3.7. Diffraction-limited IR speckle masking observations of the central regions of Seyfert galaxies

  • M. Wittkowski (a1) (a2), Y. Balega (a3), T. Beckert (a2), W.J. Duschl (a1) (a2), K.-H. Hofmann (a1) and G. Weigelt (a1)...

Metrics

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed