... NGC 1808

Based on observations made with ESO Telescopes at the Paranal Observatory under programme ID 68.B-0264(A).

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... respectively

These filters are both 0.05 $\mu$m wide and have very similar spectral responses relative to their central wavelengths. The overall instrumental response to a flat continuum source is the same for both filters. Further, the NB_3.28 filter is well matched to both the shape of the PAH feature and to the redshift of the sources considered here. Indeed, it is with these criteria in mind that the source selection was made.

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... 1.5

http://www.eso.org/instruments/isaac/drg/html/drg.html

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...

As we show in Sect. 4.4 there is also a strong morphological correspondence between the lower surface brightness PAH feature emission and the extended H$~\alpha$ emission. Thus the lack of Pa$~\alpha$ emission at the position of the extended PAH feature emission likely is due to the depth of the exposure at Pa$~\alpha$.

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... emission

In the interest of clarity, we have not shown K-band contours in Fig. 4. For these contours the reader is referred to Fig. 2 (right) of TGSE96.

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... position

Kalas and Wynn-Williams use the mean of the emission at 3.18 $\mu$m and 3.38 $\mu$m to represent the continuum underlying the PAH feature emission at 3.28 $\mu$m. As stated in Sect. 3, the emission at 3.38 $\mu$m is contaminated by a weaker PAH feature at 3.4 $\mu$m (Sturm et al. 2000, and references therein), resulting in an overestimate of the continuum. Nevertheless if one uses their tabulated 3.18 $\mu$m measurement as the continuum the feature-to-continuum ratio for their Peak 1 (0.98) is still low relative to that of their Peak 2 (2.13).

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... emission

Forbes et al. (2000) suggest that the predicted value for radio continuum flux is overestimated as a result of the presence of dense gas in the region (Paglione et al. 1995).

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