VLBI Observations of H2O Maser Annual Parallax and Proper Motion in IRAS 20143+3634: Reflection on the Galactic Constants

Abstract

We report the results of VLBI observations of H${}_2$O masers in the IRAS 20143+3634 star forming region using VERA (VLBI Exploration of Radio Astronomy). By tracking masers for a period of over two years we measured a trigonometric parallax of $\pi =0.367\pm 0.037$ mas, corresponding to a source distance of $D=2.72_{-0.25}^{+0.31}$ kpc and placing it in the Local spiral arm. Our trigonometric distance is just 60% of the previous estimation based on radial velocity, significantly impacting the astrophysics of the source. We measured proper motions of $-2.99\pm 0.16$ mas yr${}^{-1}$ and $-4.37\pm 0.43$ mas yr${}^{-1}$ in R.A. and Decl. respectively, which were used to estimate the peculiar motion of the source as $(U_s,V_s,W_s)=(-0.9\pm 2.9,-8.5\pm 1.6,+8.0\pm 4.3)$ km s${}^{-1}$ for $R_0=8$ kpc and ${\Theta }_0=221$ km s${}^{-1}$, and $(U_s,V_s,W_s)=(-1.0\pm 2.9,-9.3\pm 1.5,+8.0\pm 4.3)$ km s${}^{-1}$ for $R_0=8.5$ kpc and ${\Theta }_0=235$ km s${}^{-1}$. IRAS 20143+3634 was found to be located near the tangent point in the Cygnus direction. Using our observations we derived the angular velocity of Galactic rotation of the local standard of rest (LSR), ${\Omega }_0=27.3\pm 1.6$ km s${}^{-1}$ kpc${}^{-1}$, which is consistent with previous values derived using VLBI astrometry of SFRs at the tangent points and Solar circle. It is higher than the value recommended by the IAU of ${\Omega }_0=25.9$ km s${}^{-1}$ kpc${}^{-1}$ which was calculated using the Galactocentric distance of the Sun and circular velocity of the LSR.

arXiv commentIntended for PASJ VERA special issue Updated version: V2: Corrected typos Removed incorrect phrase regarding the evolutionary stage of IRAS20143, in the conclusions, that had remained in the paper since a far earlier draft version V3: Update email address

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Cited by in corpus (9)

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• The Gould Belt, the de Vaucouleurs-Dolidze Belt, and the Orion Arm
• Detection of periodic variations in vertical velocities of Galactic masers
• Parameters of the Link between the Optical and Radio Frames from Gaia DR2 Data and VLBI Measurements
• Analysis of Galactic Rotation from Masers based on a Nonlinear Oort Model