LBA Observations

Simultaneous with the ATCA observations, the source PKS 1934-638 was also observed with the Parkes and Mopra telescopes thus forming a Long Baseline Array (LBA) with three telescopes, and three different baselines. The baseline lengths are: ATCA-Mopra 113 km, Mopra-Parkes 207 km, and ATCA-Parkes 321 km. PKS 1934-638 was observed for a total of about 6 h. After each hour, approximately, the bandpass calibrator PKS 1921-293 was observed. This source has a similar flux density to PKS 1934-638 (12.6 Jy, compared with 15.1 Jy), and was also observed for a total of 5 h. Integration times on the Parkes baselines were slightly less owing to the longer slew time of this antenna. The data for each telescope was recorded onto an S2 tape recorder at a bandwidth of 8 MHz. Both hands of circular polarisation were recorded. The ATCA data for the five telescopes on the 3 km track was converted from linear to circular and coherently summed before recording. The observations are summarized in table

The LBA data were subsequently correlated at ATNF headquarters in Epping. Astronomical delay terms were applied at this stage, and a channel spacing of 15.6 kHz and an integration time of 5 sec was used for the cross-correlated spectra. As for the ATCA-only data, this was later Hanning-smoothed, resulting in a FWHP resolution of 31.2 kHz. The data were edited and scalar-averaged. Spectra were subsequently corrected for the bandpass response on a baseline-by-baseline basis.

**Table:** A summary of the ATCA and LBA observing parameters and results for 1353-341, 1814-637 and 1934-638. Subsequent lines give the observing frequency, the secondary calibrator, the bandpass calibrator, the observing date (YY/MM/DD), the array, the integration time (in hours), the rms noise, the flux density, the peak optical depth $\tau$ , the redshift at peak, the uncertainty on the redshift, the equivalent width, the velocity dispersion of the main component $\sigma$ , the velocity width FWZI, the column density (for T=100 K) calculated from EW.
	1353-341	1814-637	1934-638
$\nu$	1161 MHz	1336 MHz	1201 MHz
Secondary
calibrators	1215-457	1934-638	1921-293
Bandpass
calibrators	1934-638	1934-638	1921-293
Observing Date	98/01/16	98/01/17	95/09/15
Array	6A	6A	6D, LBA
Integration time	5 h	1 h	6 h
rms noise	5 mJy	6 mJy	7 mJy, 5 mJy
Flux Density	0.64 Jy	13.2 Jy	15.1 Jy
$\tau$	0.125	0.217	0.0022
z	0.222495	0.063979	0.182819
	$\pm$ 0.000008	$\pm0.000003$	$\pm0.000003$
EW (km s^-1)	21.2	9.5	0.062
$\sigma$ (km s^-1)	66	19	8
FWZI( km s^-1)	496	372	101
N $_{\rm H I}$ (100)	$21\times10^{20}$	$9\times10^{20}$	$0.06\times10^{20}$