Gaku Saito

Large-scale mapping observations of the CI 3P1-3P0 line toward heiles cloud2 in the Taurus Dark Cloud

A distribution of the neutral carbon atom (C i) in Heiles cloud 2 (HCL2) has been investigated with the Mount Fuji submillimeter-wave telescope. A region of 1.2 deg 2 covering a whole region of HCL2 has been mapped with the 3 P1‐ 3 P0 fine-structure line (492 GHz) of C i. The global extent of the C i emission is similar to that of 13 CO, extending from southeast to northwest. However, the C i intensity is found to be rather weak in dense cores traced by the line of C 18 O. On the other hand, strong C i emission is observed in a south part of J= 1‐0 HCL2 in which the C 18 O intensity is fairly weak. The C i/CO abundance ratio is greater than 0.8 for the C i peak, whereas it is 0.1 for the dense cores such as the cyanopolyyne peak. The C i‐rich cloud found in the south part may be in the early evolutionary stage of dense core formation where C i has not yet been converted completely into CO. This result implies that formation of dense cores is taking place from north to south in HCL2. Subject headings: ISM: atoms — ISM: clouds — ISM: evolution — ISM: individual (Heiles’s cloud 2)

The Mt. Fuji submillimeter-wave telescope

We have developed a 1.2 m submillimeter-wave telescope at the summit of Mt. Fuji to survey emission lines of the neutral carbon atom (CI) toward the Milky Way. A superconductor-insulator-superconductor mixer receiver on the Nasmyth focus is used to observe the 492 GHz band in SSB and the 345 GHz band in DSB simultaneously. The receiver noise temperature is 300 K in SSB and 200 K in DSB for 492 and 345 GHz, respectively. The intermediate frequency frequency is 1.8–2.5 GHz. An acousto-optical spectrometer which has the total bandwidth of 0.9 GHz and 1024 channel outputs has also been developed. The telescope was installed at the summit of Mt. Fuji (alt. 3725 m) in July 1998. It has been remotely operated via a satellite communication system from Tokyo or Nobeyama. Atmospheric opacity at Mt. Fuji was 0.4–1.0 at 492 GHz during 30% of the time and 0.07–0.5 at 345 GHz during 60% of the time from November 1998 to February 1999. The system noise temperature was 1000–3000 K in SSB at 492 GHz and 500–2000 K in DSB ...

Large-Scale Mapping Observations of the C [CSC]i[/CSC] ([TSUP]3[/TSUP][ITAL]P[/ITAL][TINF]1[/TINF]–[TSUP]3[/TSUP][ITAL]P[/ITAL][TINF]0[/TINF]) and CO ([ITAL]J[/ITAL] = 3–2) Lines toward the Orion A Molecular Cloud

Large-scale mapping observations of the 3P1-3P0 fine-structure transition of atomic carbon (C i, 492 GHz) and the J=3-2 transition of CO (346 GHz) toward the Orion A molecular cloud have been carried out with the Mount Fuji submillimeter-wave telescope. The observations cover 9 deg2 and include the Orion Nebula M42 and the L1641 dark cloud complex. The C i emission extends over almost the entire region of the Orion A cloud and is surprisingly similar to that of 13CO (J=1-0). The CO (J=3-2) emission shows a more featureless and extended distribution than C i. The C i/CO (J=3-2) integrated intensity ratio shows a spatial gradient running from the north (0.10) to the south (1.2) of the Orion A cloud, which we interpret as a consequence of the temperature gradient. On the other hand, the C i/13CO (J=1-0) intensity ratio shows no systematic gradient. We have found a good correlation between the C i and 13CO (J=1-0) intensities over the Orion A cloud. This result is discussed on the basis of photodissociation region models.

Plan of receiver development for ASTE/LMSA

We present a plan of heterodyne receivers for Atacama Submillimeter Telescope Experiment (ASTE), which is one of Japanese R&D project of Large Millimeter Submillimeter Array (LMSA) and Atacama Large Millimeter Array (ALMA). A new 10 m submillimeter-wave telescope has been pre-installed at Nobeyama since February 2000 and will be installed at Pampa la Bola (el. 4800 m) in northern Chile. The telescope has four receiver layouts: (1) A shaped Cassegrain optics was designed for the Nobeyama operation to achieve high beam-efficiency at millimeter-wave bands. (2) Normal Gaussian optics will be replaced for the Chile operation to optimize submillimeter- wave bands up to 850 GHz. (3) It is possible to install an ALMA prototype receiver at the focus of secondary reflector. (4) An optics for submillimeter SIS photon camera. We describe the 350 GHz receiver which noise temperature was around 55 K in the frequency band of 330 - 360 GHz. The temperature ripple at the 4 K stage of two stages Gifford-McMahon refrigerator has been reduced to be less than 10 mK by employing a He-pot temperature stabilizer.

Large-Scale Mapping Observations of the C i (3P1–3P0) and CO (J = 3–2) Lines toward the Orion A Molecular Cloud

Large-scale mapping observations of the 3P1-3P0 fine-structure transition of atomic carbon (C i, 492 GHz) and the J=3-2 transition of CO (346 GHz) toward the Orion A molecular cloud have been carried out with the Mount Fuji submillimeter-wave telescope. The observations cover 9 deg2 and include the Orion Nebula M42 and the L1641 dark cloud complex. The C i emission extends over almost the entire region of the Orion A cloud and is surprisingly similar to that of 13CO (J=1-0). The CO (J=3-2) emission shows a more featureless and extended distribution than C i. The C i/CO (J=3-2) integrated intensity ratio shows a spatial gradient running from the north (0.10) to the south (1.2) of the Orion A cloud, which we interpret as a consequence of the temperature gradient. On the other hand, the C i/13CO (J=1-0) intensity ratio shows no systematic gradient. We have found a good correlation between the C i and 13CO (J=1-0) intensities over the Orion A cloud. This result is discussed on the basis of photodissociation region models.

Large-scale mapping observations of the CI(3P1-3P0) and CO(J=3-2) lines toward the Orion A molecular cloud

Large-scale mapping observations of the 3P1-3P0 fine-structure transition of atomic carbon (C i, 492 GHz) and the J=3-2 transition of CO (346 GHz) toward the Orion A molecular cloud have been carried out with the Mount Fuji submillimeter-wave telescope. The observations cover 9 deg2 and include the Orion Nebula M42 and the L1641 dark cloud complex. The C i emission extends over almost the entire region of the Orion A cloud and is surprisingly similar to that of 13CO (J=1-0). The CO (J=3-2) emission shows a more featureless and extended distribution than C i. The C i/CO (J=3-2) integrated intensity ratio shows a spatial gradient running from the north (0.10) to the south (1.2) of the Orion A cloud, which we interpret as a consequence of the temperature gradient. On the other hand, the C i/13CO (J=1-0) intensity ratio shows no systematic gradient. We have found a good correlation between the C i and 13CO (J=1-0) intensities over the Orion A cloud. This result is discussed on the basis of photodissociation region models.