Annual Parallax Measurements of an Infrared Dark Cloud MSXDC G034.43+00.24

摘要

We have measured the annual parallax of the H_2O maser associated with an infrared dark cloud, MSXDC G034.43+00.24, with VERA. The parallax is 0.643 ± 0.049 mas, corresponding to a distance of 1.56 _(?0.11)~(+0.12) kpc. This value is less than half of the previous kinematic distance of 3.7 kpc. We revised the core-mass estimates of MSXDC G034.43+00.24 from the previous estimations of 1000M _⊙ to hundreds of M _⊙. The spectral type is still consistent with that of the massive star.