HI in HO: Hoag's object revisited
  We present new HI observations of Hoag's Object obtained with the Westerbork
Synthesis Radio Telescope (WSRT). The data show that the luminous optical ring
around the elliptical body has a bright HI counterpart that shares the
kinematical properties of the optical ring. The entire HI structure is twice as
large as the optical ring and shows a mild warp in its outer regions relative
to the inner ring. We detect two additional HI sources close in redshift to
that of Hoag's Object, and report on a newly identified SDSS optical companion
galaxy. The HI sources are ~0.3 and ~1 Mpc away in projected distance, and the
companion galaxy is also ~1 Mpc away. Our main conclusion is that the HI
detected in Hoag's Object shows no indication that this galaxy has experienced
a recent (less than ~1 Gyr ago) accretion event. At least one of the two
additional HI detected objects does not have an optical counterpart. One
possibility is that this object is an HI filament left over from an interaction
shaping Hoag's Object, in which case this interaction must also have occurred
at least 1-2 Gyr ago.
