A Search for Dust Emission in the Leo Intergalactic Cloud
  We present a search for infrared dust emission associated with the Leo cloud,
a large intergalactic cloud in the M96 group. Mid-infrared and far-infrared
images were obtained with IRAC and MIPS on the Spitzer Space Telescope. Our
analysis of these maps is done at each wavelength relative to the HI spatial
distribution. We observe a probable detection at 8 microns and a marginal
detection at 24 microns associated with the highest HI column densities in the
cloud. At 70 and 160 microns, upper limits on the dust emission are deduced.
The level of the detection is low so that the possibility of a fortuitous
cirrus clump or of an overdensity of extragalactic sources along the line of
sight can not be excluded. If this detection is confirmed, the quantities of
dust inferred imply a dust to gas ratio in the intergalactic cloud up to a few
times solar but no less than 1/20 solar. A confirmed detection would therefore
exclude the possibility that the intergalactic cloud has a primordial origin.
Instead, this large intergalactic cloud could therefore have been formed
through interactions between galaxies in the group.
