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   71191
   The Leo-I group (D=11 Mpc) of galaxies harbours a huge (d=200 kpc)
   intergalactic HI ring orbiting an E galaxy and probably interacting
   with the spiral galaxy M96. In our previous ASCA data we have detected
   (2-3 sigma) a shadow in the X-ray background from an HI concentration
   in the ring and diffuse emission around M96 in the direction of the HI
   ring. We propose to map the main HI concentration of the ring in 3 deep
   exposures for studying the shadow and map out shadows from even denser
   parts of the ring. This will give (i) a clean measurement of the
   relative Galactic and extragalactic contributions to the soft X-ray
   background (ii) constrain the origin of the ring and (iii) settle
   whether M96 and the ring is interacting with important implications for
   the extragalactic distance scale.
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