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東京大学・天文学教育研究センターでは2003年4月から談話会を開いています。
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ML: semiadm _at_ ioa.s.u-tokyo.ac.jp
please replace _at_ with @
Language: 英語 (English)
Abstract: At high spectral resolution, the [C II] 158 mm and [O I] 63 mm lines exhibit ubiquitous absorption and self-absorption features that are difficult to reconcile with emission arising solely from photodissociation regions associated with OB star clusters. We instead propose that these features originate in the photodissociated “skins” of molecular clouds externally illuminated by the ambient interstellar radiation field (ISRF). Meudon PDR models show that a standard Habing field produces surface layers with moderate optical depths in [C II] (τ ~ 0.5) and larger optical depths in [O I] (τ ~ 2–5), along with subthermal excitation temperatures (Tₑₓ ~ 10–20 K). Under these conditions, the surface layers naturally produce absorption against bright continuum sources and self-absorption against bright line emission. Detailed modeling of the Nessie A cloud reproduces the observed line profiles well. An examination of the HYGAL SOFIA survey toward 25 bright continuum sources shows that these features are common, including absorption or self-absorption at the systemic velocity of the star-forming cloud, multiple absorption components from foreground clouds at distinct velocities, and systematically stronger absorption in [O I] than in [C II]. Because all clouds are exposed to the ISRF, this mechanism is likely widespread. In extragalactic observations, coarse spectral resolution can wash out these absorption features, leading to a significant underestimate of the intrinsic [C II] and [O I] line emission.
| # | Date | Speaker | Title | Chair |
| 441 | 2026年5月28日(木) 15:30-16:30 | James Jackson (NRAO, USA) | [C II] and [O I] Absorption and Self-Absorption from the “Skins” of Clouds | I. Sakon |
詳細はこちら: 令和8(2026)年度談話会
| # | Date | Speaker | Title | Chair |
| 440 | 2026年4月16日(木) 15:00-16:00 | Joss Bland-Hawthorn (Director, Sydney Institute for Astronomy, U Sydney) | The long-term evolution of turbulent discs in high-redshift galaxies | 天文教室と共催 |
| 439 | 2026年4月14日(火) 16:15-17:15 | Donald Figer (Rochester Institute of Technology, USA) | Photon Counting CMOS Imaging Detectors for Optical and UV Astrophysicss | 天文教室と共催 |
