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Astron. Astrophys. 320, 957-971 (1997)

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2. Observations

The observations were carried out with the IRAM 30-m telescope at Pico de Veleta (Spain). Table 1 summarizes the observed molecules, transitions and frequencies. For [FORMULA], Table 1 only gives the frequency of the [FORMULA] component. The other K transitions were also observed simultaneously in the 512x1 MHz contiguous filter backends. This Table also gives the typical single sideband system temperature, the half power beam width (HPBW) and the beam efficiency of the radiotelescope. We mapped the [FORMULA] J=5-4 line in a region of [FORMULA], with HPBW spacing. We also observed the J=5-4, J=8-7 and J=12-11 transitions of [FORMULA] simultaneously with a 6 arcsec spacing in the region around the Sgr B2M and Sgr B2N sources. Spectra of the J=8-7 and J=6-5 lines were also taken at selected positions out of the central region. The two 512 [FORMULA] MHz channel filter bank and the 864 channel acustoptic spectrometer were used as backends. The velocity resolution provided by these spectrometers was 3.2, 2.7, 2.0, 0.8 [FORMULA] for the 3.3, 2.7, 2 and 1.4 mm lines respectively. The spectra were taken in position switching and we measured 5 on source positions for one reference spectrum. Pointing was checked frequently on the continuum emission maxima, Sgr B2M and Sgr B2N.


Table 1. List of molecules, transitions and observing parameters

Within the spectrometer we also observed the H41 [FORMULA] (92.034 GHz), and H35 [FORMULA] (147.046 GHz) radio recombination lines simultaneously. These lines, which trace the ionized material, were also used to check for pointing errors. The [FORMULA] J=11-10 transition was observed in the image band when observing the [FORMULA] J=5-4 line.

Most of the observations were made with the receiver tuned to SSB mode with an image band rejection of 7 to 9 dB. The line intensity calibration was done measuring cold and ambient temperature loads. The intensity scales are given in antenna temperature [FORMULA], and for the small sized sources the line intensities have been converted to main beam brightness temperatures by using the beam efficiencies in Table 1 and a forward efficiency of 0.9.

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© European Southern Observatory (ESO) 1997

Online publication: June 30, 1998