Up: HI observations of nearby
Subsections
Observations were performed with three different radio telescopes
for different declination ranges. The 100-m radiotelescope at Effelsberg
was used for declinations greater than
,
the Nançay radio
telescope was selected for galaxies in the declination range
,
and the compact array of the Australia Telescope was used for
galaxies south of
.
The radio telescope at Effelsberg has been used in the total power mode
(ON - OFF) combining a reference field 5 min earlier in R.A. with the
on-source position. A dual channel HEMT receiver had a system noise of
30 K.
The 1024 channel autocorrelator was split into 4 bands (bandwidth 6.25 MHz)
of 256 channels each
shifted in frequency by 5 MHz with respect to their neighbor in order to
cover a velocity range from -470 to 3970 kms-1 overlapping 1.5
MHz between channels.
The resulting channel separation was 5.1 kms-1 yielding a
resolution of 6.2 kms-1 (10.2 kms-1 after Hanning
smoothing). The HI profiles observed with the 100-m radiotelescope
are presented in Fig. 1 in order of increasing R.A. as in Table1.
The half power beam widths (HPBW) of the Effelsberg
telescope at this wavelength is 9
3.
For 15 galaxies in the declination range
the Nançay radio telescope was used with the same velocity
resolution and coverage. Major differences to the description given for
the Effelsberg observations were a different system noise (45 K), a
different antenna beam (
in R.A. and Dec.
for this declination range), and shorter
integration phases with a cycle of 2 minutes for the ON and the OFF
positions. Nine galaxies have been detected (Fig.2).
40 of the 57 galaxies south of declination
have been observed
with the Compact Array of the Australia Telescope.
For this HI search we have chosen the 750A antenna array configuration
in order
to yield an antenna beam comparable to the optical size
of the smallest galaxies (i.e.
1
). The frequency setup and
correlator configuration was such that we obtained a velocity coverage
from -450
to +2900 kms-1 and a channel separation of 6.6 kms-1
(i.e. a resolution of 7.9 kms-1).
Each galaxy was observed for 10 min every few hours. With five to six
observations per target position we achieved a regular coverage of the
uv plane for these
"snapshot mode'' observations.
The resulting integrated HI profiles are given in Fig. 3 (for a more
detailed discussion of these data see Huchtmeier et al. in preparation).
We may miss some flux with the interferometer (missing flux) as the
observed HI emission extends over more than 2
per channel for
over 60% of the galaxies.
Galaxies from the kk98 sample not observed are: kk11, kk63, kk179,
kk184, kk189,
kk190,
kk197, kk203, kk211, kk213, kk214, kk217, kk221, kk222,
kk235, kk244, kk248.
Up: HI observations of nearby
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