We made phase-referencing Very Long Baseline Interferometry (VLBI) observations of Galactic 22 GHz H2O maser sources with VLBI Exploration of Radio Astrometry (VERA). We measured the parallax dis- tances of G48.61+0.02, G48.99-0.30, G49.19-0.34, ON1, IRAS 20056+3350, IRAS 20143+3634, ON2N, and IRAS 20126+4104, which are located near the tangent point and the Solar circle. The angular ve- locity of the Galactic rotation at the LSR (i.e. the ratio of the Galactic constants) is derived using the measured parallax distances and proper motions of these sources. The derived value of Ω0 = 28:8  1:7 km s-1 kpc-1 is consistent with recent values obtained using VLBI astrometry but 10% larger than the International Astronomical Union (IAU) recommended value of 25.9 km s-1 kpc-1 = (220 km s-1) / (8.5 kpc).

ABSTRACT
1. INTRODUCTION
2. OBSERVATIONS
3. RESULTS
4. DISCUSSION
REFERENCES

• Takumi Nagayama(Mizusawa VLBI Observatory, National Astronomical Observatory of Japan)
• Toshihiro Omodaka(Graduate School of Science and Engineering, Kagoshima University)
• Toshihiro Handa(Graduate School of Science and Engineering, Kagoshima University)
• Hideyuki Kobayashi(Mizusawa VLBI Observatory, National Astronomical Observatory of Japan)
• Ross A. Burns(Graduate School of Science and Engineering, Kagoshima University)