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Paper: Superbubble Motion Away from the Galactic Plane: Astrometry of Water Masers in NGC 281 with VERA
Volume: 402, Approaching Micro-Arcsecond Resolution with VSOP-2: Astrophysics and Technologies
Page: 476
Authors: Sato, M.; Hirota, T.; Honma, M.; Kobayashi, H.; VERA Project Team
Abstract: We report on results of our parallax measurements of an H2O maser source in the NGC 281 West molecular cloud, associated with a ∼300-pc fragmenting superbubble above the Galactic plane. We have conducted multi-epoch phase-referencing observations of the maser source with VERA (VLBI Exploration of Radio Astrometry) over 18 months year since May 2006. The parallax measurement yields a direct distance estimate of 2.82±0.24 kpc, which agrees well with the photometric distance of 2.94±0.15 kpc derived by Guetter and Turner (1997) and resolves the large distance discrepancy of NGC 281 in previous studies. We find that the H2O maser features in NGC 281 West are systematically moving toward the southwest and further away from the Galactic plane with a vertical velocity of ∼20 km s−1. Our new results provide the most direct evidence for the NGC 281 superbubble expansion is most likely driven by multiple or sequential supernova explosions in the Galactic plane.
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