An Intermediate Velocity HI Cloud Falling to the Galactic Disk; Possible
  Evidence for Low Metallicity HI Gas Originated Outside the Galactic Disk
  We found that an intermediate velocity cloud (IVC) IVC 86-36 in HI 21 cm
emission shows a head-tail distribution toward the Galactic plane with marked
parallel filamentary streamers, which is extended over 40 degrees in the sky.
The distance of IVC 86-36 is constrained to be less than ~3 kpc from absorption
of a background star as determined from opticalspectroscopy. There is a bridge
feature in velocity between the IVC and the local ISM with velocity separation
of ~50 km s-1, which may indicate dynamical interaction of the IVC with the
disk. If the interaction is correct, the distance estimate d of the IVC ranges
from 200 pc to 3 kpc, and the mass of the IVC head is estimated to be
7X103(d/1kpc)2Msol. The IVC shares similar properties to the Smith cloud
located at 12 kpc, including the head-tail distribution, streamers, and bridge
feature, while the mass of the IVC is less than ~0.1 of the Smith cloud. A
comparison between the Hi and the Planck/IRAS dust emission indicates that the
dust emission of IVC 86-36 is not detectable in spite of its HI column density
of 2X10^20 cm-2, indicating low metalicity of IVC 86-36 by a factor of ~< 0.2
as compared with the solar neighbor. We conclude that IVC 86-38 is an infalling
cloud which likely originated in the low-metallicity environment of the
Galactic halo or the Magellanic system.
