The parameters of Gaussian fits to the detected lines are given in Table 2. Spectra are displayed in Fig. 1. Since not all lineshapes are exactly Gaussian, we have also determined the integrated line intensities by adding the channels with emission, calculating the errors from the rms noise per channel. The results are identical, with the errors of the Gaussian typically being slightly larger than the errors obtained using the rms noise.
We detected mm wavelength transitions toward all galaxies that were observed, although the detection of the line in NGC 6946 is tentative.
Toward NGC 253, four of the five transitions observed could be detected; in M 82, all five lines were found. The three positions observed in M 82 are detected in the line, while the line is not seen toward the (10 ,10 ) offset. Toward this position, the twin lines thus have different intensities.
In IC 342, four out of six transitions were detected. It is interesting to note that the transition was detected both toward the central and (tentatively) toward an offset position, while its twin transition, the line, only observed toward the offset position, was not detected at an rms level of 12 mK. As in M 82, the intensities of the twin lines differ. Toward the center, the line is considerably stronger than its counterpart, the transition, which is not detected. Toward a northern offset position however, the line is stronger than the (tentatively detected) line.
Toward Maffei 2, two out of four lines were found. The profiles show a double peaked structure. This double feature is also visible in the HNC(1-0) transition (Hüttemeister et al. 1995), but is not seen in other molecular species.
The results of Gaussian fits for all observations of single positions are given in Table 3; spectra are displayed in Fig. 2. We also obtained a map of NGC 253 in the transitions at 145 GHz with a 10 spacing (Fig. 3).
As is the case for the transitions at 96 GHz, the 'line' is actually a blend of several individual transitions (see Table 1) with frequencies ranging from 145.09375 GHz to 145.13346 GHz, corresponding to a velocity shift of 82 . We adopted a rest frequency of 145.10323 GHz, corresponding to the transition. The transitions were detected with relative ease in all sources we observed, with the notable exception of M 82. In Maffei 2, the line was also easily detected. The transition in NGC 253 is clearly detected.
© European Southern Observatory (ESO) 1997
Online publication: April 20, 1998