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Astron. Astrophys. 325, 473-478 (1997)

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2. H I -observations

Observations were performed using the 100-m radiotelescope at Effelsberg which has a half power beam width of 9.3' at the wavelength of 21cm. The 1024-channel autocorrelator was split into four filter banks (256 channels each) using a bandwidth of 12.5 MHz which yielded a resolution of 12 km/s or 20 km/s after Hanning smoothing. A typical observing time of 60 min per source yielded a r.m.s. noise of 3 mJy (the system noise was 30K). An ON-source position was combined with an OFF-source position every 5 minutes. This total-power mode improves the baseline behavior of the spectra. Regular measurements of well known continuum sources were used to control pointing and calibration of the telescope. Every two to three hours a well known line source (e.g. dwarf galaxies) was observed as a system check. The toolbox software of the MPIfR was used for the data reduction. The observed spectra were corrected for moderately curved baselines only which should not introduce additional errors for the derived velocity and flux measurements.

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© European Southern Observatory (ESO) 1997

Online publication: April 28, 1998