Astron. Astrophys. 363, 917-925 (2000)

4. Warm and cold dust component

For further investigation of the knots, modified Planck curves have been fitted to the SEDs. We assumed an emissivity law of . Only the points at 60, 100, and 175 µm have been fitted. Except for Knot 32 (close to the centre), all knots require (at least) two dust components with different temperatures to fit the data.

In order to fit two modified Planckians four parameters (two temperatures and two intensities), have to be determined with three data points now available (at 60, 100 and 175 µm). Therefore the temperature of the warmer component had to be fixed. A temperature of 40 K has been chosen in accordance with previous investigations (Walterbos & Schwering 1987). Note, that the value itself has no physical meaning, as the flux density at 60 µm is already influenced by transiently heated very small dust grains. However, when hold constant for the whole knot sample, it allows for a reasonable parameterized comparison of the sources and their dust properties.

© European Southern Observatory (ESO) 2000

Online publication: December 5, 2000
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