7.7.4.2 Giant Molecular Clouds and Dark Nebulae
In parallel with the Orion region, molecular-line observations of GMCs associated
with HII regions (W 51, NGC 7538, S 140) and MCs associated with dark nebulae
(L1551, B335, B1) were widely carried out at Nobeyama.
Among these, NGC 7538 was observed by Kameya Osamu and his group
(in 1986–1990) with CS, SO lines and H 2 O masers. NGC 7538 is a bright HII
region adjoined by a molecular cloud in its southeast side. In the core region of the
molecular cloud, Kameya’ group found three high-velocity flows, one was associated with compact HII regions and one was associated with a reflection nebula. All of
these high-velocity regions are possibly bipolar and associated with infrared sources.
They showed that these cores are the candidate sites of the high-velocity molecularoutflows combined with active star formation (Kameya and Takakubo 1988;
Kameya et al. 1989).
Molecular line observations of Lynds dark nebula L1551 (one of the MCs) were
made by Kaifu Norio’s group (1984) and Uchida Yutaka, Kaifu Norio and their
group (1987). Kaifu’ group used 45-m telescope and found a rotating disk (Kaifu,
Suzuki et al. 1984) while Uchida’ group, using the Millimeter Array in CO line,
observed the detailed structure of rotating disk and bipolar flow. They depicted the
overall structure as shown in Fig. 7.38. (Uchida et al. 1987). As the result, they found
that both lobes had a clear hollow cylindrical structure and that both lobes were
likely spinning with a velocity of 1 ~ 2 km s
À1 in the same direction as that of the
disk found by Kaifu and his group in 1984. These characteristics were well explained
by the magnetohydrodynamic theory proposed by Uchida Yutaka and Shibata
Kazunari, who stressed the role of magnetic field in producing such flows (Kaifu
et al. 1984; Uchida and Shibata 1985).
7.7.5 The Galactic Center
The Galactic Center is located at the radio source Sgr A, as discovered in the radio
observations in the mid-1950s. This was confirmed by IR observations in the 1960s.
Fig. 7.38 Schematic
picture of L1551 (Uchida
et al. 1987)
7.7 The Galaxy
221
In parallel with the Orion region, molecular-line observations of GMCs associated
with HII regions (W 51, NGC 7538, S 140) and MCs associated with dark nebulae
(L1551, B335, B1) were widely carried out at Nobeyama.
Among these, NGC 7538 was observed by Kameya Osamu and his group
(in 1986–1990) with CS, SO lines and H 2 O masers. NGC 7538 is a bright HII
region adjoined by a molecular cloud in its southeast side. In the core region of the
molecular cloud, Kameya’ group found three high-velocity flows, one was associated with compact HII regions and one was associated with a reflection nebula. All of
these high-velocity regions are possibly bipolar and associated with infrared sources.
They showed that these cores are the candidate sites of the high-velocity molecularoutflows combined with active star formation (Kameya and Takakubo 1988;
Kameya et al. 1989).
Molecular line observations of Lynds dark nebula L1551 (one of the MCs) were
made by Kaifu Norio’s group (1984) and Uchida Yutaka, Kaifu Norio and their
group (1987). Kaifu’ group used 45-m telescope and found a rotating disk (Kaifu,
Suzuki et al. 1984) while Uchida’ group, using the Millimeter Array in CO line,
observed the detailed structure of rotating disk and bipolar flow. They depicted the
overall structure as shown in Fig. 7.38. (Uchida et al. 1987). As the result, they found
that both lobes had a clear hollow cylindrical structure and that both lobes were
likely spinning with a velocity of 1 ~ 2 km s
À1 in the same direction as that of the
disk found by Kaifu and his group in 1984. These characteristics were well explained
by the magnetohydrodynamic theory proposed by Uchida Yutaka and Shibata
Kazunari, who stressed the role of magnetic field in producing such flows (Kaifu
et al. 1984; Uchida and Shibata 1985).
7.7.5 The Galactic Center
The Galactic Center is located at the radio source Sgr A, as discovered in the radio
observations in the mid-1950s. This was confirmed by IR observations in the 1960s.
Fig. 7.38 Schematic
picture of L1551 (Uchida
et al. 1987)
7.7 The Galaxy
221