Masanori Yoshizawa

Is the vorticity vector of the galaxy perpendicular to the galactic plane? II: Kinematics of the galactic warp

A warping motion inherent in the galactic warp is detected, based on the proper motions of about 2000 young generation stars which consist of O-B5 stars, supergiants and bright giants of any spectral type in the heliocentric distance interval 0.5 to 3.0 kpc. To examine the warping motion, the overall pattern analysis of the proper motions of these stars is performed on the basis of the three-dimensional Ogorodnikov-Milne model, instead of the classical Oort-Lindblad model. It is found that the kinematics of these stars is quite different from that of K-M giants which, as has been demonstrated in the previous work (Paper I), show only the familiar plane-parallel galactic rotation described by the Oort constants A and B

Long-baseline optical fiber interferometer instruments and science

Developments of fiber linked optical interferometer are reported. This interferometer is a part of MIRA-I.2 interferometer (Mitaka InfraRed and optical Array). MIRA-I.2 is an optical interferometer with a 30 meters long baseline. It consists of two 30cm siderostats, tip-tilt mirrors, vacuum pipes delay lines and detectors. We plan to use two 60 meters long polarization-maintaining fibers for arms of the interferometer, instead of vacuum pipes. The developments include dispersion and polarization compensation of fiber and fiber injection module. In laboratory experiments, dispersion compensation succeeded. The fringe visibility was 0.93 for wide-band, where the central wavelength of light was 700nm, and bandwidth was 200nm, while 0.95 with a He-Ne laser. We used BK7 glass wedge for dispersion compensation. About fiber injection module, basic optical design has completed. The results of our fiber interferometer could contribute to OHANA (Optical Hawaiian Array for Nanoradian Astronomy) project. We present new science targets, white dwarves and T Tauri stars, and an 800 m delayline concept in CFHT for the project.

Experiments with the fiber-connected interferometer for the MIRA project

Fiber optics is useful for connecting the element telescopes of a long-baseline interferometer. Experiments with a fiber- connected interferometer are carried out as a part of MIRA- I.2 interferometer under construction. MIRA-I.2 is an interferometer consisting of two 300 mm siderostats which are placed on a 30 m south-north baseline. For this baseline, it is necessary to use fibers of about 100 m long. Fiber optics will be essential for the interferometric connection of large telescopes, such as Subaru, Gemini, and Keck on the summit of Mauna Kea. In this case, fiber length of about 1 km is needed. We achieved white light fringes using 10 m and 100 m fibers. With the 10 m fiber, visibility of 0.7 was achieved for both He-Ne laser and white light sources. Visibility of 0.7 for white light was obtained by compensating the dispersion effect of fiber with glass plates. Experiments will be extended to longer fibers such as 1000 m.

Development of the optical and infrared interferometer MIRA-I.2

The MIRA-1.2 system consists of two siderostats, beam reducers, vacuum delay liens, baseline metrology system, tip-tilt mirrors, beam combine optics, and fringe detector. Two siderostats, of which aperture of the flat mirror is 300mm, are placed apart by 4 meters in the north-south direction. Beam reducer is a Cassegrain optics with the paraboloidal primary and secondary mirrors of the diameter D1 equals 200mm and D2 equals 30mm, respectively. The metrology system with laser interferometers is set up to stabilize the baseline length for astrometry. Piezo-driven tip-tilt mirrors are equipped for the correction of image motions due to the air turbulence and other errors. Delay lines are placed in a vacuum tube. Experiments of the fiber optics is carried out as a part of MIRA-1.2. Developing MIRA-1.2 system, it is aimed to establish the basic techniques of astrometry and future projects, especially of MIRA-II.

MIRA-II, MIRA-III, and MIRA-SG projects: the future plan of long-baseline optical/IR interferometer in Japan

Long-baseline optical and IR interferometers are being considered as future astronomical instrument plans in Japan since 1994. They are called MIRA projects, indicating Mitaka or Mauna Kea IR array. The next Mitaka optical and IR array proposal is called MIRA-II. It consists of four fixed telescopes as an array for 1mas astrometry and three movable ones for 0.2mas imaging. They are placed in a sideways T- configuration with three 128m arms and extended lines getting the longest baseline of 680m. Each of the telescopes is a 30cm siderostat added with a 20cm beam compressing telescope. MIRA-III is a proposal of Mauna Kea optical/IR array including a 1.4km baseline with 1.5m telescopes. Its shape is a modified Y-configuration. It also aims at precise astrometry including many quasars as well as high resolution imaging of fainter stellar objects than MIRA-II. MIRA-SG, a future proposal of Mauna Kea optical/IR array connecting Subaru with GEMINI, is one of the largest interferometer with an 800m baseline by 8m telescopes. It became possible by using optical fibers fed from each Cassegrain focus with an adaptive optics system. Keck telescopes and other large telescopes on Mauna Kea are also candidates to connect with Subaru.

Mitaka optical and InfraRed Array first stage (MIRA-I.1) instruments

Mitaka optical and InfraRed Array first stage (MIRA-I.1) was built following the first fringe detection with the previous first stage instrument called MIRA-I, rearranging its optics. It consisted of two 13 cm-diameter telescopes, collimator lens producing 8 mm propagation beams, long, fine, and fast delay lines, fringe and scintillation sensors, quadrant sensors and tip-tilt mirrors, and so on. MIRA-I.1 was operated from October 19998 to march 1999 and succeeded to get fringes of nine stars, to make stellar diameter observations, to make stellar fringe tracking experiments, and to obtain atmospheric characteristics of Mitaka site.

Polarimetric stellar interferometry by use of birefringent retarders

We propose a polarimetric technique for a stellar interferometer that uses two birefringent retarders inserted into each arm of the interferometer. The retarders shift the interference fringes of the two orthogonal polarizations to opposite directions along an optical path difference (OPD), which enables us to measure the polarized fringe visibilities separately. Laboratory demonstrations were carried out using quartz retarders with a thickness of 1.124 mm, and the separation of the interferometric fringes of +/-10 microm along the OPD was observed. We discuss a calibration method for the acquired fringes to obtain reliable estimations of polarized fringe visibilities. We also discuss feasibility of the proposed technique for the Mitaka optical InfraRed Array (MIRA-I.2).

Recent progress at the MIRA : development of fringe tracking system

The MIRA-I.2 is a 30m baseline optical interferometer located at the Mitaka campus of the National Astronomical Observatory of Japan. After the detection of the first fringes with Vega in 2002, we have continued improvement of system performance and have demonstrated stellar diameter measurement in wide band (600nm-1000nm). Recently, we begin on development of two scientific detectors: spectrometer with separate fringe tracking system and interfeometric polarimetry. Recent progress and performance of our two system is reported.

MIRA Status Report: Recent Progress of MIRA-I.2 and Future Plans

MIRA-I.2 is a 30m-baseline two-aperture stellar interferometer working in the visible band (from 600 to 1000 nm). In this article are presented the up-to-date progress and performance of MIRA-I.2 as well as some ongoing and future plans. The fast and coarse delay lines are now both evacuated, and the maximum OPD (optical path delay) compensations are about 16 m and 4 m long, respectively, for the fast and coarse delay lines. The current limiting magnitude is about I=4.5mag, and stars within the declination range from +8 to +51 degree is possible to be observed longer than one hour at the elevation angle of 60 degrees and higher. The OPD of the coarse delay line is modulated by about 128 micrometers around the expected fringe center with the use of PZT, and 187 fringe packets are scanned during one shot (= 60 seconds duration) to yield the mean visibility of about 10 % internal errors for each shot. The thermal environment of the building that houses the delay lines and interference optics has been improved very much, and readjustments of the optical alignment are not necessary for a whole night. The assembly and the setup of the optics to be used for the fringe tracking experiment are nearly completed.

MIRA-I.2: recent progress

After the first fringe detection with MIRA-I.2 30m baseline for Vega in June 2002, fringes for Vega and Deneb has been confirmed and then construction continued. Fast delay line has been evacuated and extended from 4m to 8m long. Coarse delay line has been extended from 2m to 4m. Baseline vector has been determined with 0.1mm accuracy. Aluminized mirrors have been changed to gold-plated ones, and the total throughput has become four times larger than before at the 600nm-1000nm band. The photon rate is 150 per ms for a 2 mag (I-band) star and the present limiting magnitude is better than 3mag. A delay modulation PZT has been set to push a cats eye retro-reflector. Observations have been made for 6 stars with successful fringe packet detections. Visibility stability has been being studied with artificial light sources and Vega, which preliminary results are better than a few percent. A three-color system between 600-1000nm is now on the half way of installation. Gregorian cats eye retro-reflectors with fine delay line PZTs and fringe tracking control software is planned to be installed.