Amazing Light pp 521-541 | Cite as

Far-infrared Imaging of the HII Region-Molecular Cloud Complex W51A with a Balloon-borne Telescope

  • Francesco A. Pepe
  • Roland Brodbeck
  • Daniel Huguenin
  • Fritz K. Kneuböhl


Star formation is a field of high interest in astrophysics. In recent years, considerable effort has been made in order to understand the processes of star formation. Molecular clouds, in which star formation takes place, and dust associated with these clouds extinguish all short-wavelength radiation up to the near-infrared. Consequently, protostars and young stars cannot be observed directly and, therefore, one is restricted to study the dust and gas surrounding them. By means of continuum radio astronomy free-free emission from compact or more extended sources can can be mapped. These maps trace regions in which gas is highly ionized by ultra-violet (UV) radiation emitted by nearby or embedded stars. Quantitative measurements imply restrictions to the number and the spectral type of the stars. Studies on molecular line emission provide additonal information concerning physical conditions, composition and dynamics of the clouds. These lines are most frequent in the submillimeter- and millimeter-wavelength region. By constrast, dust emission is contionuous and is observed in the far-infrared (FIR). Its broad-band spectrum can be approximated by a gray-body function with an emissivity which varies slightly with wavelenght. The bulk of this radiation falls into the wavelength range between 30 μm and 300 μm.


Optical Depth Star Formation Molecular Cloud Column Density Dust Emission 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag New York, Inc. 1996

Authors and Affiliations

  • Francesco A. Pepe
  • Roland Brodbeck
  • Daniel Huguenin
  • Fritz K. Kneuböhl

There are no affiliations available

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