TRIGONOMETRIC DISTANCE AND PROPER MOTION OF IRAS 20056+3350: A MASSIVE STAR FORMING REGION ON THE SOLAR CIRCLE

Abstract

We report our measurement of the trigonometric distance and proper motion of IRAS 20056+3350, obtained from the annual parallax of H2O masers. Our distance of D = 4.69 +0.65 −0.51 kpc, which is 2.8 times larger than the near kinematic distance adopted in the literature, places IRAS 20056+3350 at the leading tip of the Local arm and proximal to the Solar circle. Using our distance we re-evaluate past observations to reveal IRAS 20056+3350 as a site of massive star formation at a young stage of evolution. This result is consistent with the spectral energy distribution of the source evaluated with published photometric data from UKIDSS, WISE, AKARI, IRAS and sub-millimetre continuum. Both analytical approaches reveal the luminosity of the region to be 2.4×10 4 L⊙, and suggest that IRAS 20056+3350 is forming an embedded star of ≥16M⊙. We estimated the proper motion of IRAS 20056+3350 to be (µ�cos�, µ�) = (−2.62±0.33, −5.65±0.52) mas yr −1 from the group motion of H2O masers, and use our results to estimate the angular velocity of Galactic rotation at the Galactocentric distance of the Sun, 0 = 29.75±2.29 km s −1 kpc −1 ,