We observed the M81 galaxy group in order to detect a possible HI
bridge between two galaxies. HI observations taken with the Jodrell Bank
Telescope showed both a previously-undetected galaxy, HIJASS
J1021+6842, as well as a possible bridge between this galaxy another
member, IC 2574 (Boyce et al. 2001). Our observations were a follow-up
to this paper in attempt to confirm the existence of an HI bridge.

The observation strategy included combining both new VLA observations
of the IC 2547-HIJASS J1021+6842 system with existing spectral line
data. In order to guarantee that the data could be used together, we
used the same correlator and channel settings for our observations as
for the existing data. Multiple pointings were taken and then
mosaicked together to cover both galaxies on the sky. Due to
interference from the Galaxy, calibrator observations were taken at
frequencies sandwiching the frequency of the source, and solutions
were then interpolated across the source data frequencies.

The data were reduced in AIPS using the standard method, first by
flagging the data and then by applying necessary calibrations (SETJY,
CALIB, GETJY, CLCAL). The data were then written to fits files and
read into the MIRIAD program for imaging, due to its powerful ability
to mosaic multiple-pointing datasets. The cube was imaged and then
Cleaned.

However, the aforementioned interference from the Galaxy prevented any
definitive measure of an HI bridge. In the channels at which the
bridge would have appeared, the Galaxy was also detected in the
data. Its signal overwhelmed any signal from a tentative bridge, so we
are unable to place a limit on the flux of the bridge based on our
noise level. We therefore can give no conclusive evidence to support
or disprove its existence.


References

Boyce, P.J., Minchin, R.F., Kilborn, V.A., Disney, M.J., Lang, R.H.,
Jordan, C.A., Grossi, M., Lyne, A.G., Cohen, R.J., Morison, M.I., and
Phillipps, S., 2001, ApJL 560, L127