Galactic Small Scale Structure Revealed by the GALFA-HI Survey
  The Galactic Arecibo L-band Feed Array HI (GALFA-HI) survey is mapping the
entire Arecibo sky at 21-cm, over a velocity range of -700 to +700 km/s (LSR),
at a velocity resolution of 0.18 km/s and an angular resolution of 3.5 arcmin.
The unprecedented resolution and sensitivity of the GALFA-HI survey have
resulted in the detection of many isolated, very compact HI clouds at low
Galactic velocities which are distinctly separated from the HI disk emission.
In the limited area of ~4600 deg$^2$ searched so far, we have detected 96 such
compact clouds. The detected clouds are cold with kinetic temperature less than
300 K. Moreover, they are quite compact and faint, with median values of 5
arcmin in angular size, 0.75 K in peak brightness temperature, and
$5\times10^{18}$ cm$^{-2}$ in HI column density. From the modeling of spatial
and velocity distributions of the whole compact cloud population, we find that
the bulk of clouds are related to the Galactic disk, and are within a few kpc
distance. We present properties of the compact clouds sample and discuss
various possible scenarios for the origin of this clouds population and its
role in the Galactic interstellar medium studies.
