Yuji Arikawa

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)

Atomic carbon and CO isotope emission in the vicinity of DR 15

We present observations of the P-3(1)-P-3(o) fine-structure transition of atomic carbon [C I], the J = 3-2 transition of CO, and the J = 1-0 transitions of (CO)-C-13 and (CO)-O-18 toward DR 15, an H II region associated with two mid-infrared dark clouds (IRDCs). The (CO)-C-13 and (CO)-O-18 J = 1-0 emissions closely follow the dark patches seen in optical wavelength, showing two self-gravitating molecular cores with masses of 2000 and 900 M-circle dot, respectively, at the positions of the cataloged IRDCs. Our data show a rough spatial correlation between [C I] and (CO)-C-13 J = 1-0. Bright [C I] emission occurs in the relatively cold gas behind the molecular cores but does not occur in either highly excited gas traced by CO J = 3-2 emission or in the H II region/molecular cloud interface. These results are inconsistent with those predicted by standard photodissociation region models, suggesting an origin for interstellar atomic carbon unrelated to photodissociation processes.

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.

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.

Submillimeter-wave and millimeter-wave observations of the interaction of supernova remnants with molecular clouds

We report on submillimeter-wave and millimeter-wave observations toward supernova remnants (SNRs) by using the James Clerk Maxwell Telescope, the Mt. Fuji submillimeter-wave telescope, and the Nobeyama 45-m radio telescope. For the supernova remnant W28, which is an EGRET gamma-ray source, we have convincingly detected the broad CO, HCO+, HCN, and SiO emission lines from the shock-accelerated gas due to the SNR-cloud interaction. The previously-reported 1720-MHz OH maser spot is found to be located at the shock front. By using the Mt. Fuji submillimeter-wave telescope, we observed the 492-GHz CI (neutral atomic carbon), 345-GHz CO (3–2) and 330-GHz 13CO (3–2) emission toward SNRs, W44 and W51B/C. We found that the CI/CO and CI/13CO intensity ratio tends to be high in the SNR-cloud interaction region in W51B/C SNR. This fact might suggest the CI relative abundance is enhanced by the interaction, not only in the SNR IC 443, but also in W51B/C SNR.

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.