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Ishiguro, M.

Publications and source records attributed to Ishiguro, M..

7 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

Identification of Optical Component of North Toroidal Source of Sporadic Meteors and its Origin

We succeeded to identify the North Toroidal source by optical observations performed by the SonotaCo Network, which is a TV observation network coordinated by Japanese amateurs. This source has been known only for radar observations until now. The orbits of the optical meteors in the North Toroidal source are relatively large eccentricity and semi-major axis, compared with those of the radar meteors. In this paper, we report the characteristics of this North Toroidal source detected by optical observations, and discuss the possible origin and evolution of this source.

Hashimoto, T.↗
NASA NTRS2003

The Tagish Lake Meteorite as a Possible Sample from a T or D Type Asteroid

Since the Tagish Lake meteorite fell in January 2000, the one of the kind meteorite has become the hottest issue among meteoriticists as well as astrobiologists. Meanwhile, concerning the physical origin of the meteorite in our solar system, only Hiroi et al. reported that it likely came from a D asteroid based on comparison of their visible-near-infrared (Vis-NIR) reflectance spectra. However, because asteroid classification is usually performed based on a limited range of wavelength, the asteroid classes and surface compositions may not necessarily have one-to-one correspondence. Also, Hiroi et al. precluded the T-type asteroids simply because their average albedo is much higher than the visible reflectance of Tagish Lake although their spectral matches with Tagish Lake were good, and the 3-mm band spectra compiled in were not enough to compare the degree of hydration or kinds of hydrous minerals between primitive asteroids and Tagish Lake. In this paper, we employ more spectral datasets up to the 3-mm range to address the possible connection between two particular asteroids, 773 Irmintraud and 308 Polyxo, and the Tagish Lake meteorite.

Hiroi, T.↗
NASA NTRS1993

Interferometric observations for oxygen-containing organic molecules toward Orion-KL

High spatial resolution observations were made for the 3 mm transitions of methanol (CH3OH), methyl formate (HCOOCH3), and dimethyl ether (/CH3/2O) toward Orion-KL using the Nobeyama Millimeter Array. The 15(3)-14(4) A(-) CH3OH emission appears to be elongated along the line connecting IRc2 and 'the southern condensation (SC)', which may suggest a relation between methanol and the outflow from IRc2. The HCOOCH3 (7(1,6)-6(1,5)) and (CH3)2O (15(2,13)-15(1,14)) emissions appear to be well concentrated toward SC with an angular size of about 6.5 arcsec. There also exists another oxygen-rich condensation to the west of IRc2 having column densities of HCOOCH3 and (CH3)2O comparable to those of SC. We derive the total column densities 6.8 x 10 exp 16/sq cm, 1.4 x 10 exp 16/sq cm, and 2.7 x 10 exp 16/sq cm for CH3OH, HCOOCH3, and (CH3)2O, respectively, at the core of SC.

Minh, Y. C.↗
NASA NTRS1993

Observations of IRAS F10214+4724 at the Nobeyama millimeter array

F10214+4724 is an IRAS source at z=2.286 with L(sub FIR) approximately 10(exp 14) solar luminosity. The CO(3-2) emission was detected at the NRAO 12-m telescope, and its molecular gas mass was estimated to be (1-3)x10(exp 11) solar mass. This object is unique and important because it is the first high-z object from which molecular line emission is detected and it enables us to investigate molecular gas content, star forming material, at an early stage of galactic evolution. If IRAS F10214+4724 is a primeval galaxy at the formation process, it is possible the gas has not been collapsed yet to the galactic scale. On the other hand, it is also possible IRAS F10214+4724 is a merging or interacting system like the most of ultra-luminous infrared galaxies. However, since the first detection was made with a medium size single-dish telescope, the precise position, extent, and distribution of the molecular gas had not been determined. The aim of our aperture synthesis observations is therefore to determine position and distribution of molecular gas.

Sakamoto, K.↗
NASA NTRS1986

Dark filaments observed at 8.3mm and 3.1mm wavelength

Mapping of the sun was made at 3.1mm (98 GHz) and 8.3mm (36 GHz) wavelengths with a 45m dish radio telescope at the Nobeyama Cosmic Radio Observatory. The depressions associated with large H alpha filaments are derived to be -0.2 at 8.3mm and -0.05 at 3.1mm, which are darker than the values inferred by Raoult et al. (1979)

Hiel, E.↗
NASA NTRS1986

Polar-cap and coronal-hole-associated brightenings of the Sun at millimeter wavelengths

Mapping observations of the Sun at millimeter wavelengths were made on 16 to 22 July 1984 with the 45-m telescope of the Nobeyama Radio Observatory. Seven 36-GHz (8.3-mm) maps and five 98-GHz (3.1-mm) maps were taken with half-power beam widths of 46 arc sec and 17 arc sec, respectively. Instead of the conventional rastering technique, a radial-scan method was adopted in which every scan passes through the disk center. Accordingly, the variation of the atmosphere attenuation due to changes in the weather conditions can be easily estimated and removed by using the brightness values at the disk center as calibration data. Also, the pointing errors of the telescope due to the high-speed scans can be corrected by using the solar limbs as position references. The rms residual errors in relative brightness and position after the corrections were estimated to be approx. 2% and approx. 5 arc sec respectively. To further reduce these errors, enabled us to make high-quality maps with with or approx. 1% uncertainty in brightness. Here and in the following, brightness is expressed in terms of the average brightness of the solar disk as a unit. Note that the brightness temperature of the quiet Sun is approx. 8000 K and approx. 6000 K at 36 GHz and 98 GHz, respectively.

Kosugi, T.↗