2. Observations, data reduction
The observations were made with the IRAM interferometer on Plateau de Bure, France, with four 15m antennas (Guilloteau et al. 1992) between November 1995 and April 1996. Each antenna of the interferometer was equipped with a dual channel receiver tuned to frequencies 109.3 GHz and 228.7 GHz, corresponding to 13CO(1-0) and 12CO(2-1). The tracking center of the interferometer was , (J2000), close to the nucleus of the galaxy. The recession velocity of the galaxy is . See DRSR for a table with the astrophysical parameters of the galaxy.
The interferometer was used in 3 configurations, giving baselines between 20m and 180m. After Fourier transform of the visibilities and restoration by the CLEAN algorithm, we obtained channel maps of both transitions with a velocity width. The observational parameters are summarised in Table 1, including the clean beam parameters and the final noise in channel maps.
Table 1. IRAM interferometer parameters.
© European Southern Observatory (ESO) 1999
Online publication: June 18, 1999