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Paper: VLA Imaging of H2O Masers in NGC 6240 and M 82
Volume: 320, The Neutral ISM in Starburst Galaxies
Page: 179
Authors: Hagiwara, Y.
Abstract: The H2O masers in the two starforming galaxies, NGC6240 and M82, were observed with the NRAO Very Large Array (VLA) to follow-up the previous single-dish detections. VLA observations revealed that the red-shifted maser in NGC6240 marks exactly the center of the southern nucleus. The large red-shift (∼ 450 km s−1) of the maser might be due to the infall of gas in the merger/interacting galaxy or the jet-activity of an AGN, rather than a rotating disk. The blue-shifted maser in the starforming galaxy M82 remains unresolved with the VLA resolution of 0.1 arcsec, or ∼ 1.75 pc (D=3.5 Mpc), however, the maser was marginally detected by the follow-up MERLIN observations. It appears that the maser is barely resolved at 0.02 arcsec (∼ 0.35 pc). The maser is not associated with any continuum sources such as ultra-compact HII regions or radio SNRs. The maser in M82 could have been formed in the early stage of extragalactic starformation.
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