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2. Observations

The observations were carried out on February 1990 with the 37 m radio telescope at Haystack Observatorygif. We observed the (J,K) = (1,1) and the (J,K) = (2,2) inversion transitions of the ammonia molecule. At the observing frequencies (23.6944960 GHz and 23.7226320 GHz, respectively), the beam size of the telescope is tex2html_wrap_inline3065, and its beam efficiency at an elevation of tex2html_wrap_inline3067 is tex2html_wrap_inline3069. We used a dual maser receiver and both polarizations were observed. The spectrometer was a 1024-lag digital autocorrelator with an effective bandwidth of 6.67 MHz. The calibration was made with the standard noise-tube method. The observations were made in the position switching mode. All the spectra were corrected for the elevation-dependent gain variations and for atmospheric attenuation. The rms pointing error was estimated to be tex2html_wrap_inline3071 by observing continuum unresolved sources. System temperature ranged from 70 to 150 K. The data were reduced using the CLASS and GREG packages of IRAM. The observed spectra were smoothed, resulting a velocity resolution of tex2html_wrap_inline3073 tex2html_wrap_inline3075.

We searched 15 sources for tex2html_wrap_inline3077(1,1) emission. In all cases, we first made measurements on a five-point grid centered at the positions given in Table 1 (click here), with a full beam separation between points. The tex2html_wrap_inline3079(1,1) line was detected in 14 of these sources. The tex2html_wrap_inline3081(2,2) line was observed in 8 sources, at the positions given in Table 2 (click here), and was detected in 6 of them. Spectra of the tex2html_wrap_inline3083(1,1) and tex2html_wrap_inline3085(2,2) lines obtained at the positions given in Table 2 (click here) are shown in Figs. 2 (click here) and 2 (click here), respectively. In Figs. 3.1 (click here) to 3.10 (click here), 3.11 (click here) to 3.12.1 (click here), and 3.13 (click here), we show the tex2html_wrap_inline3087(1,1) maps of the detected sources.

  Table 1: Sources observed in tex2html_wrap_inline3089 or tex2html_wrap_inline3091

In Table 2 (click here) we give tex2html_wrap_inline3203(1,1) and (2,2) line parameters obtained from a multicomponent fit to the observed spectra at the position of the emission peak, using the CLASS package. In Table 2 (click here) we list physical parameters of the high-density cores, derived from the ammonia observations following the procedures explained in the footnotes of the table.

Table 2: tex2html_wrap_inline3205 line parameterstex2html_wrap_inline3207

Table 3: Physical parameters of the tex2html_wrap_inline3579 condensations

Additionally, we searched for the 6tex2html_wrap_inline3845 tex2html_wrap_inline3847 maser line (at the observing frequency of 22.235080 GHz) in nine sources. We made five or seven-point maps centered at the positions given in Table 1 (click here). For the water maser observations, we used the same spectrometer with the same bandwidth as for the ammonia observations. We reached a typical sensitivity of 1.5 Jy (tex2html_wrap_inline3849) per spectral channel. We detected tex2html_wrap_inline3851\ maser emission towards the region associated with the source IRAS 20188+3928 and the spectrum obtained is shown in Fig. 2 (click here). For the other observed sources we do not detect any significant (tex2html_wrap_inline3855) tex2html_wrap_inline3857\ emission.

  figure446
Figure 1: Spectra of the (J,K)=(1,1) inversion transition of the tex2html_wrap_inline3861 molecule towards the positions given in Table 2, for the detected sources. The vertical axis is the main beam brightness temperature and the horizontal axis is the velocity with respect to that of the center of the main line (given in Table 2)

  figure453
Figure 2: Same as Fig. 1, for the (J,K)=(2,2) inversion transition

  figure458
Figure 3: Spectrum of the tex2html_wrap_inline3865 maser detected near IRAS 20188+3928, towards the position tex2html_wrap_inline3869, tex2html_wrap_inline3871, as observed in Feb. 10, 1990


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