Trigonometric parallax of IRAS 22555+6213 with VERA: Three-dimensional view of sources along the same line of sight

Abstract

Abstract We report the results of the measurement of the trigonometric parallax of an H2O maser source in IRAS 22555+6213 with the VLBI Exploration of Radio Astrometry (VERA). The annual parallax was determined to be 0.314 ± 0.070 mas, corresponding to a distance of $3.18^{+0.90}_{-0.66}\,{\rm kpc}$. Our results confirm IRAS 22555+6213 to be located in the Perseus arm. We computed the peculiar motion of IRAS 22555+6213 to be (Usrc, Vsrc, Wsrc) = (4 ± 4, −32 ± 6, 8 ± 6) km s−1, where Usrc, Vsrc, and Wsrc are directed toward the Galactic center, in the direction of Galactic rotation and toward the Galactic north pole, respectively. IRAS 22555+6213, NGC 7538, and Cepheus A lie along the same line of sight, and are within 2° on the sky. Their parallax distances, with which we derived their absolute position in the Milky Way, show that IRAS 22555+6213 and NGC 7538 are associated with the Perseus Arm, while Cepheus A is located in the Local Arm. We compared the kinematic distances of IRAS 22198+6336, G108.18+05.51, G108.20−00.58, G108.47+02.81, G108.59+00.49, Cepheus A, NGC 7538, G111.23−01.23, G111.25−00.76, and IRAS 22555+6213 derived with flat and non-flat rotation curves with their parallax distance and found the kinematic distance derived from the non-flat rotation assumption (−5 to −39 km s−1 lag) to be consistent with the parallax distance.