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Appendix A: Near-Infrared images

Figure A.1: K-band images showing a field of 60 $\hbox {$^{\prime \prime }$ }$$\times$60 $\hbox {$^{\prime \prime }$ }$ with the sources located in the image centres, greyscales with logarithmic contours.

The J- and K-band images look very similar, therefore only the K-band images are shown (Fig. 10). Most of the emission is concentrated, but also irregular/extended tails are present. The pointlike blue source 10 $\hbox {$^{\prime \prime }$ }$ southwest of 00262+4251, and the two ones located about 6 $\hbox {$^{\prime \prime }$ }$ north and south of 18090+0130 are probably stars (and are excluded from the photometry). The photometry derived from the images is listed in Table 1.

Appendix B: Optical spectra

Figure B.1: Spectra of 20046-0623 (top) and 21504-0628 (bottom), blue (left) and red (right) channel of the TWIN spectrograph.

Figure 11 shows optical spectra for two sources, obtained with the TWIN spectrograph at the 3.5 mtelescope on Calar Alto, Spain. Both sources have a LINER spectrum according to the line diagnostics by Veilleux & Osterbrock (1987). Now all sources of our mm-subsample are spectroscopically classified (see Table 4).