VERA astrometry toward the Perseus arm gap
  The Perseus arm has a gap in Galactic longitudes (l) between 50 and 80 deg
(hereafter the Perseus arm gap) where the arm has little star formation
activity. To better understand the gap, we conducted astrometric observations
with VERA and analyzed archival H I data. We report on parallax and proper
motion results from four star-forming regions, of which G050.28-00.39 and
G070.33+01.59 are likely associated with the gap. The measured parallaxes are
0.140+/-0.018 (mas), 0.726+/-0.038 (mas), 0.074+/-0.037 (mas), and
0.118+/-0.035 (mas) for G050.28-00.39, G053.14+00.07, G070.33+01.59, and
G079.08+01.33, respectively. Since the fractional parallax error of
G070.33+01.59 is large (0.5), we estimated a 3D kinematic distance of the
source to be 7.7+/-1.0 kpc using both the LSR velocity (VLSR) and the measured
proper motion. Perseus-arm sources G049.41+00.32 and G050.28-00.39 lag relative
to a Galactic rotation by 77+/-17 km/s and 31+/-10 km/s, respectively. The
noncircular motion of G049.41+00.32 cannot be explained by the gravitational
potential of the Perseus arm. We discovered rectangular holes with integrated
brightness temperatures of < 30 K arcdeg in l vs. VLSR of the H I data. One of
the holes is centered near (l, VLSR) = (47 deg, -15 km/s), and G049.41+00.32 is
associated with the rim of the hole. However, G050.28-00.39 is not associated
with the hole. We found extended H I emission on one side of the Galactic plane
when integrating the H I data over the velocity range covering the hole (i.e.,
VLSR = [-25, -5] km/s). G049.41+00.32 and G050.28-00.39 are moving toward the
emission. The Galactic H I disk at the same velocity range showed an arc
structure, indicating that the disk was pushed from the lower side of the disk.
All the observational results might be explained by a cloud collision with the
Galactic disk.
