arXiv subjects

Satoru Iguchi

Publications and source records attributed to Satoru Iguchi.

43 records · Page 3Linked to original sources

arXiv2011

Atacama Compact Array Correlator for Atacama Large Millimeter/submillimeter Array

We have developed a FX-architecture digital spectro-correlator, Atacama Compact Array Correlator for the Atacama Large Millimeter/submillimeter Array. The ACA Correlator processes four pairs of dual polarization signals, whose bandwidth is 2 GHz, from up to sixteen antennas, and calculates auto- and cross-correlation spectra including cross-polarization in all combinations of sixteen antennas. We report the detailed design of the correlator and the verification results of the correlator hardware.

astro-ph.IM↗

arXiv2011

Next Generation Millimeter/Submillimeter Array to Search for 2nd Earth

ALMA is a revolutionary radio telescope at present and its full operation will start from 2012. It is expected that ALMA will resolve several cosmic questions and will show a new cosmic view to us. Our passion for astronomy naturally goes beyond ALMA because we believe that the 21st-century Astronomy should pursue the new scientific frontier. In this conference, we propose a project of the future radio telescope to search for Habitable planets and finally detect 2nd Earth as a Migratable planet. The detection of 2nd Earth is one of ultimate dreams for not only astronomers but also people.

astro-ph.IM↗

arXiv2011

Atacama Compact Array Antennas

We report major performance test results of the Atacama Compact Array (ACA) 7-m and 12-m antennas of ALMA (Atacama Large Millimeter/submillimeter Array). The four major performances of the ACA antennas are all-sky pointing (to be not more than 2.0 arcsec), offset pointing (to be < 0.6 arcsec) surface accuracy (< 25(20) micrometer for 12(7)m-antenna), stability of path-length (15 micrometer over 3 min), and high servo capability (6 degrees/s for Azimuth and 3 degrees/s for Elevation). The high performance of the ACA antenna has been extensively evaluated at the Site Erection Facility area at an altitude of about 2900 meters. Test results of pointing performance, surface performance, and fast motion capability are demonstrated.

astro-ph.IM↗

arXiv2011

Proper Motion of the Sub-Parsec Scale Jet in the Radio Galaxy 3C 66B

We present proper motion of the sub-parsec scale jet in a nearby elliptical galaxy 3C 66B. Observations were made using the VLBA and partly Effelsburg 100-m telescope at 2.3 GHz and 8.4 GHz at 10 epochs over 4 years. The 8.4 GHz images showed that a proper motion increases from 0.21 to 0.70 mas/year, corresponding to an apparent speed of 0.30 c to 0.96 c, with a distance from the core on a sub-parsec scale. Our investigation suggests that the apparent increase of the proper motion can be explained by changes in the viewing angle, according to a relativistic beaming model. However, we still cannot eliminate the possibility that acceleration of the jet outflow speed or of changes of emissivity profile in the two-zone jet might be found in 3C 66B.

astro-ph.CO↗

arXiv2010

A Very Close Binary Black Hole in a Giant Elliptical Galaxy 3C 66B and its Black Hole Merger

Recent observational results provide possible evidence that binary black holes (BBHs) exist in the center of giant galaxies and may merge to form a supermassive black hole in the process of their evolution. We first detected a periodic flux variation on a cycle of $93\pm1$ days from the 3-mm monitor observations of a giant elliptical galaxy \object{3C 66B} for which an orbital motion with a period of $1.05\pm0.03$ years had been already observed. The detected signal period being shorter than the orbital period can be explained by taking into consideration the Doppler-shifted modulation due to the orbital motion of a BBH. Assuming that the BBH has a circular orbit and that the jet axis is parallel to the binary angular momentum, our observational results demonstrate the presence of a very close BBH that has the binary orbit with an orbital period of $1.05\pm0.03$ years, an orbital radius of $(3.9\pm1.0) \times 10^{-3}$ pc, an orbital separation of $(6.1^{+1.0}_{-0.9}) \times 10^{-3}$ pc, the larger black hole mass of $(1.2^{+0.5}_{-0.2}) \times 10^9$ $M_{\sun}$, and the smaller black hole mass of $(7.0^{+4.7}_{-6.4}) \times 10^8$ $M_{\sun}$. The BBH decay time of $(5.1^{+60.5}_{-2.5})\times 10^2$ years provides evidence for the occurrence of black hole mergers. This Letter will demonstrate the interesting possibility of black hole collisions to form a supermassive black hole in the process of evolution, one of the most spectacular natural phenomena in the universe.

astro-ph.GA↗

arXiv2008

The FFX Correlator

We established a new algorithm for correlation process in radio astronomy. This scheme consists of the 1st-stage Fourier Transform as a filter and the 2nd-stage Fourier Transform for spectroscopy. The "FFX" correlator stands for Filter and FX architecture, since the 1st-stage Fourier Transform is performed as a digital filter, and the 2nd-stage Fourier Transform is performed as a conventional FX scheme. We developed the FFX correlator hardware not only for the verification of the FFX scheme algorithm but also for the application to the Atacama Submillimeter Telescope Experiment (ASTE) telescope toward high-dispersion and wideband radio observation at submillimeter wavelengths. In this paper, we present the principle of the FFX correlator and its properties, as well as the evaluation results with the production version.

astro-ph↗

arXiv2002

A Helical Magnetic Field in the Jet of 3C 273

Both in the Faraday Rotation Measure and the intrinsic polarization angle, new features are revealed to indicate a helical magnetic field operating along the jet of the bright active galactic nuclei 3C 273. The helical field has been suggested to be related to the formation and collimation of jets by magnetohydrodynamic models. The distribution of the RM shows a systematic gradient with respect to the jet axis, which is expected by a helical magnetic field. In addition, the helical field can consistently explain two types in the direction of the projected magnetic field: parallel and perpendicular to the jet axis. Further, if the helical magnetic field is generated by winding up of an initial field by rotation of the accretion disk, we can uniquely determine the direction of the disk rotation, since the jet is approaching us.

astro-ph↗