As part our investigation into the Galactic rotation curve , we carried out Very Long Baseline Interferometry ( VLBI ) observations towards the star-forming region IRAS 01123+6430 using VLBI Exploration of Radio Astrometry ( VERA ) to measure its annual parallax and proper motion .
The annual parallax was measured to be 0.151 \pm 0.042 \ > { mas } , which corresponds to a distance of D = 6.61 ^ { +2.55 } _ { -1.44 } \ > { kpc } , and the obtained proper motion components were ( \mu _ { \alpha } { cos } \delta, \mu _ { \delta } ) = ( -1.44 \pm 0.15 , -0.27 % \pm 0.16 ) \ > { mas\ > yr ^ { -1 } } in equatorial coordinates .
Assuming Galactic constants of ( R _ { 0 } , \Theta _ { 0 } ) = ( 8.05 \pm 0.45 \ > { kpc } , 238 \pm 14 \ > { km\ > % s ^ { -1 } } ) , the Galactocentric distance and rotation velocity were measured to be ( R, \Theta ) = ( 13.04 \pm 2.24 \ > { kpc } , 239 \pm 22 \ > { km\ > s ^ { -1 } } ) , which are consistent with a flat Galactic rotation curve .
The newly estimated distance provides a more accurate bolometric luminosity of the central young stellar object , L _ { Bol } = ( 3.11 \pm 2.86 ) \times 10 ^ { 3 } \ > L _ { \odot } , which corresponds to a spectral type of B1-B2 .
The analysis of \atom { CO } { } { 12 } ( J = 1 – 0 ) survey data obtained with the Five College Radio Astronomical Observatory ( FCRAO ) 14 \ > m telescope shows that the molecular cloud associated with IRAS 01123+6430 consists of arc-like and linear components , which well matches a structure predicted by numerical simulation of the cloud-cloud collision ( CCC ) phenomenon .
The coexistence of arc-like and linear components implies that the relative velocity of initial two clouds was as slow as 3 – 5 \ > { km s ^ { -1 } } , which meets the expected criteria of massive star formation where the core mass is effectively increased in the presence of low relative velocity ( \sim 3 – 5 \ > { km\ > s ^ { -1 } } ) , as suggested by \citet 2014ApJ…792…63T .