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Astron. Astrophys. 336, 823-828 (1998)

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3. Data analysis

We present in Figs. 1 and 2 the L and L' band images of NGC 7469. We have also observed NGC 7469 in the M band, but it has not been detected, most probably because of the low sensitivity of the infrared detector. Thus, our current data analysis will be based on the two bands L and L'.

[FIGURE] Fig. 1. Left: L band image of NGC 7469. Right: PSF from a nearby star

[FIGURE] Fig. 2. Left: L' band image of NGC 7469. Right: PSF from a nearby star

The L and L' images show an unresolved core down to the resolution of 0.4" (130 pc) and 0.35" (110 pc) respectively, surrounded by an extended emission component, (r[FORMULA]400 pc), which does not appear as a ring like structure and could not be related to the starburst ring (Wilson et al., 1991, Mauder et al., 1994, Genzel et al., 1995), located farther away (r[FORMULA]480 pc, r[FORMULA]1.5"). Thus, in the following, we leave aside the analysis of the starburst ring which could not be detected during our observations because of too short integration times and we concentrate on the discussion of the innermost 1.4"[FORMULA]1.4".

So far, the exact performances of adaptive optics when using a faint reference for the wavefront analysis sensor have not been fully explored. Especially in the case of a slightly extended reference, there might be a slight residual astigmatism (Appendix A). In the case of NGC 7469, however, the visible nucleus is observed to be point-like and this effect is fully negligible. We ignore it hereafter.

However, to prevent any spurious effects due to the use of a PSF (from a nearby star) possibly not exactly identical to that corresponding to the NGC 7469 data, we chose not to apply any deconvolution process on the images. Measurements in the following analysis are based upon the cleaned (sky-subtracted, dead pixels removed, flat-fielded) images only.

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© European Southern Observatory (ESO) 1998

Online publication: July 27, 1998