Toshihiro Handa

Fundamental Parameters of the Milky Way Galaxy Based on VLBI Astrometry

We present analyses to determine the fundamental parameters of the Galaxy based on VLBI astrometry of 52 Galactic maser sources obtained with VERA, VLBA, and EVN. We model the Galaxy’s structure with a set of parameters, including the Galaxy center distance R0, the angular rotation velocity at the LSR Ω0, the mean peculiar motion of the sources with respect to Galactic rotation (Usrc, Vsrc, Wsrc), the rotation-curve shape index, and the V component of the Solar peculiar motions, Vˇ. Based on a Markov chain Monte-Carlo method, we find that the Galaxy center distance is constrained at a 5% level to be R0 = 8.05 ˙ 0.45 kpc, where the error bar includes both statistical and systematic errors. We also find that the two components of the source peculiar motion Usrc and Wsrc are fairly small compared to the Galactic rotation velocity, being Usrc = 1.0 ˙ 1.5 km s � 1 and Wsrc = � 1.4 ˙ 1.2 km s � 1 . Also, the rotation curve shape is found to be basically flat between Galacto-centric radii of 4 and 13 kpc. On the other hand,

Astrometry and Spatio-kinematics of H2O Masers in the Massive Star-forming Region NGC?6334I(North) with VERA

We measured the trigonometric parallax of an H2O maser source associated with the massive star-forming region NGC 6334I(North), hereafter as NGC 6334I(N), with the VLBI Exploration of Radio Astrometry. The derived annual parallax is 0.789 ± 0.161 mas, corresponding to a distance of 1.26 kpc. Using the new distance, we recalculated the physical parameters (masses and luminosities) of the dust continuum cores in the region, and the revised parameters are only ~50% of their originally reported values. We also traced 23 relative proper motions of the H2O masers associated with SMA1 (central millimeter source in the region) between epochs, which exhibit an average amplitude of maser proper motion of ~2.03 mas yr–1 (~12.22 km s–1), tracing a bipolar outflow. The bipolar outflow structure extends through ~600 mas (~720 AU), with a dynamical timescale of ~295 yr. Using an expanding flow model, we derived the most plausible dynamical center of the outflow, pointing to SMA1b (1.3 cm and 7 mm continuum source) as the outflow driving source. Based on our results and other existing parallax results, we derive the pitch angles of the Sagittarius arm as 62 ± 54 along the Galactic longitude range of ~07 – ~401 assuming a perfect logarithmic spiral. We derived the peculiar motion of NGC 6334I(N) to be –4 ± 1 km s–1 toward the Galactic center, 8 ± 2 km s–1 in the direction of the Galactic rotation, and 25 ± 2 km s–1 toward the Galactic north pole.

A 'water spout' maser jet in S235AB-MIR

We report on annual parallax and proper motion observations of H2O masers in S235ABMIR, which is a massive young stellar object in the Perseus Arm. Using multi-epoch VLBI (very long baseline interferometry) astrometry we measured a parallax of π = 0.63 ± 0.03 mas, corresponding to a trigonometric distance of D = 1.56 +0.09 −0.08 kpc, and source proper motion of (μαcos δ, μδ) = (0.79 ± 0.12, −2.41 ± 0.14) mas yr −1 . Water masers trace a jet of diameter 15 au which exhibits a definite radial velocity gradient perpendicular to its axis. 3D maser kinematics were well modelled by a rotating cylinder with physical parameters: vout = 45 ± 2kms −1 , vrot = 22 ± 3kms −1 , i = 12 ◦ ± 2 ◦ , which are the outflow velocity, tangential rotation velocity and line-of-sight inclination, respectively. One maser feature exhibited steady acceleration which may be related to the jet rotation. During our 15-month VLBI programme there were three ‘maser burst’ events caught ‘in the act’ which were caused by the overlapping of masers along the line of sight.

H2O masers in a jet-driven bow shock: episodic ejection from a massive young stellar object

We report the results of VERA multi-epoch VLBI 22 GHz water maser observations of S255IR-SMA1, a massive young stellar object located in the S255 star forming region. By annual parallax the source distance was measured as D = 1.78 +-0.12 kpc and the source systemic motion was (u alpha cos d, u d) = (-0.13 +- 0.20, -0.06 +- 0.27) mas yr-1. Masers appear to trace a U-shaped bow shock whose morphology and proper motions are well reproduced by a jet-driven outflow model with a jet radius of about 6 AU. The maser data, in the context of other works in the literature, reveal ejections from S255IR-SMA1 to be episodic, operating on timescales of ~1000 years.

GROUND-BASED Paα NARROW-BAND IMAGING OF LOCAL LUMINOUS INFRARED GALAXIES. I. STAR FORMATION RATES AND SURFACE DENSITIES

Luminous infrared galaxies (LIRGs) are enshrouded by a large amount of dust, produced by their active star formation, and it is difficult to measure their activity in the optical wavelength. We have carried out Pa

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

\alpha

VLBI astrometry of AGB variables with VERA: A Mira-type variable T Lepus

narrow-band imaging observations of 38 nearby star-forming galaxies including 33 LIRGs listed in

Development of a new calibration method for ground-based Paschen-alpha imaging data

IRAS

Trigonometric distance and proper motions of H2O maser bowshocks in AFGL 5142

RBGS catalog with the Atacama Near InfraRed camera (ANIR) on the University of Tokyo Atacama Observatory (TAO) 1.0 m telescope (miniTAO). Star formation rates (SFRs) estimated from the Pa

STAR FORMATION IN THE MOLECULAR CLOUD ASSOCIATED WITH THE MONKEY HEAD NEBULA: SEQUENTIAL OR SPONTANEOUS?

\alpha