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 very long baseline interferometry (VLBI) observations of H2O masers in the IRAS 20143+3634 star-forming region (SFR) using VERA (VLBI Exploration of Radio Astrometry). By tracking masers for a period of over two years we measured a trigonometric parallax of π = 0.367 ± 0.037 mas, corresponding to a source distance of $D = 2.72 ^{+0.31}_{-0.25}$ 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 ± 0.16 mas yr−1 and −4.37 ± 0.43 mas yr−1 in RA and Dec, respectively, which were used to estimate the peculiar motion of the source as (Us, Vs, Ws) = (−0.9 ± 2.9, −8.5 ± 1.6, +8.0 ± 4.3) km s−1 for R0 = 8 kpc and Θ0 = 221 km s−1, and (Us, Vs, Ws) = (−1.0 ± 2.9, −9.3 ± 1.5, +8.0 ± 4.3) km s−1 for R0 = 8.5 kpc and Θ0 = 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), Ω0 = 27.3 ± 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 International Astronomical Union of Ω0 = 25.9 km s−1 kpc−1 which was calculated using the Galactocentric distance of the Sun and circular velocity of the LSR.

The local spiral structure of the Milky Way

“…Details about the observations and data analysis are available in the Supplementary Materials. References (23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)…”

“…Parallax and proper motion data and fits for G213.70−12.60. References (23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39) Correlated data from both groups of bands were divided into separate data files, corrected for ionospheric delays using total electron content models, and residual multi-band delays were determined for all sources. Dispersive "ionosphere-only" delays were formed by differencing the delays at 4.3 and 7.3 GHz, and then scaled to 6.7 GHz.…”

Parameters of the Link between the Optical and Radio Frames from Gaia DR2 Data and VLBI Measurements

“…Young stars from the Gould Belt, the distances to which have been measured by VLBI, constitute a significant fraction of our sample. Using data on 55 such stars (they are all presented in our table as PMS, YSO, and T Tau), found the following parameters based on relation (7): a = −0.073 ± 0.034 mas and b = +0.9947 ± 0.0066. The value of these parameters are in excellent agreement with our estimates (8).…”

Analysis of galactic rotation from masers based on a nonlinear oort model

“…Figure 1 shows an example of the Galactic rotation curve, V circ = |Rω|, constructed with parameters (9), where the velocities of 106 masers are plotted. As can be seen from the figure, the rotation curve describes satisfactorily the distribution of maser rotation velocities in the range 4 < R < 12 kpc.…”