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Appendix A: Detection of HC₃N

The ratio of HC₃N J = 10–9 over HCN J = 1–0 integrated intensities is plotted in Fig. A.1 against the HCN J = 1–0 signal to noise ratio (SNR). The graph clearly shows that the non-detections are not caused by the sensitivity limit of our observations. In a wide range of SNR values, detections and non-detections coexist.

The line in Fig. A.1 shows a first order fit through the HC₃N detections, excluding the low-SNR detection in NGC 7771 (number 12 on the graph). Our detection limits (arrows in the graph) are, on average, 3 times fainter than the expected intensity derived by the fit. This means that in most of the cases – this may not be true for NGC 2273, number 19 in the graph – we do not detect HC₃N not because of a lack of sensitivity, but because the emission is intrinsically faint. In NGC 1068 the molecular emission is about one order of magnitude brighter than in the other galaxies of the sample, therefore the HC₃N detection (with the lowest HC₃N/HCN ratio in the sample) in this galaxy may be only caused by its intrinsic high luminosity.

	Fig. A.1 Ratio of HC3N J = 10–9 over HCN J = 1–0 integrated intensities against the HCN J = 1–0 signal-to-noise ratio. The line shows a linear fit through the HC3N detections. See Fig. 4 for an explanation of the symbols.
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Appendix B: HCO⁺, HNC and PAHs

The strong dependence of the HCO⁺/HNC ratio with PAH equivalent width, shown in Fig. 4d, can be better understood by plotting the behaviour of the single tracers with increasing PAH EW.

In Fig. B.1 we plot the ratios HCO⁺/HCN and HNC/HCN against the PAH strength. Evidently, at high PAH EWs we have a depletion of HNC (respect to HCN) and an enhancement of HCO⁺. This two trends both contribute to the fast decrease of the HCO⁺/HNC ratio seen in Fig. 4d. For a discussion, see text in Sect. 5.10.

	Fig. B.1 Line ratios of HCO+ and HNC over HCN against the PAH equivalent width. Notice the decrease of HNC and increase of HCO+ at high PAH EWs, to be compared with Fig. 4d.
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Appendix C: Comparison with the literature

In Table C.1 we compare our observations with literature data from Baan et al. (2008). Antenna temperatures, obtained with EMIR, were translated into flux densities, by applying the Jy/K conversion factor (C.1)with F_eff forward efficiency, and η_A antenna efficiency of the 30 m telescope at 88 GHz.

Appendix D: EMIR Spectra

In Figs. D.1–D.3 we show the spectra observed in all the galaxies in the sample. The intensities are in , not corrected for beam efficiency (see Table 2). On the x-axis we plot the sky frequency in GHz, not corrected for redshift. The position of the main emission lines is also shown.

Fig. D.1 Observed spectra in the 88 GHz band. The intensity scale is in , not corrected for main beam efficiency. The main molecular transitions are labelled regardless of line detection. The C2H 3/2 and 1/2 labels mark the limits of the C2H multiplet at 87 GHz. Transitions of vibrationally excited HC3N are labelled as v71e and v71f. The frequency scale is the observed frequency, not corrected for redshift.

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	Fig. D.1 continued.
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	Fig. D.1 continued.
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	Fig. D.1 continued.
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	Fig. D.1 continued.
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	Fig. D.2 Non-detections in the 88 GHz band. See caption of Fig. D.1.
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Fig. D.3 Observed spectra in the 112 GHz band. The intensity scale is in , not corrected for main beam efficiency. The region marked with (1 / 10) around the CO 1–0 line was scaled down by a factor 10. The main molecular transitions are labelled regardless of line detection. Transitions of vibrationally excited HC3N are labelled as v71e and v71f. The frequency scale is the observed frequency, not corrected for redshift.

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	Fig. D.3 continued.
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	Fig. D.3 continued.
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Appendix E: Derived line properties

© ESO, 2011