Our observations were made throughout the period between December 1998 and October 1999, using a total of about 150 hours of telescope time. We obtained our observations in total power (position-switching) mode using consecutive pairs of two-minute on- and two-minute off-source integrations. Off-source integrations were taken at approximately E of the target position. The autocorrelator was divided into two pairs of cross-polarized receiver banks, each with 512 channels and a 6.4 MHz bandpass. This yielded a channel spacing of 2.64 kms-1 and an effective velocity resolution of 3.3 kms-1, which was smoothed to a channel separation of 13.2 and a velocity resolution of 15.8 kms-1 during the data reduction, in order to search for faint features. The centre frequencies of the two banks were set to the known redshifted H I frequency of the target.
We reduced our H I spectra using the standard Nançay spectral line reduction packages available at the Nançay site. With this software we subtracted baselines (generally third order polynomials), averaged the two receiver polarizations, and applied a declination-dependent conversion factor to convert from units of to flux density in mJy. The -to-mJy conversion factor is determined via a standard calibration relation established by the Nançay staff through regular monitoring of strong continuum sources. This procedure yields a calibration accuracy of 15%. In addition, we applied a flux scaling factor of 1.26 to our spectra based on statistical comparisons (see Matthews et al. 1998; Matthews & van Driel 2000) of Nançay data of samples of late-type spirals with past observations of these galaxies made at Nançay and elsewhere.
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