SIMBAD references

Seventy years after the start of radio astronomical observations and over 50 years after the first observations of the 21 cm Hi line, a seemingly 'routine' Hi survey at Jodrell Bank of an already thoroughly studied part of the local Universe - the Virgo Cluster - has yielded a surprising result: the detection of what appear to be two isolated Hi clouds in the cluster, without optical counterparts, with Hi masses of about 10⁸ M_☉ (for an assumed distance of 16 Mpc) and angular sizes of about 4' to 6', or 20-30 kpc, estimated from follow-up Arecibo Hi observations. Their estimated peak Hi column density of 4x10¹⁹ atoms/cm² may be too low for star formation. Hi synthesis observations and deep CCD imaging are planned of these objects.