For a sample of 74 Shapley-Ames galaxies with high-quality radio data
at more than 3 frequencies thermal and non-thermal radio emission
were separated. Thermal fraction at 1 GHz and non-thermal spectra indices
were determined.




For the following galaxies the separation was carried out
(click on the items to get images of the spectra and of the 
confidence range of the fit parameter):


NGC 157, NGC 253, NGC 278, NGC 520, NGC 660,
NGC 891, NGC 1055, NGC 1068, NGC 1084, NGC 1309

NGC 1421, NGC 1569, NGC 2146, NGC 2207, 
NGC 2276, NGC 2903 , NGC 2964, NGC 3031, NGC 3034, NGC 3079

NGC 3166, NGC 3227, NGC 3310, NGC 3351, 
NGC 3504, NGC 3521 , NGC 3556, NGC 3593, NGC 3627, NGC 3628

NGC 3675, NGC 3810, NGC 3893, NGC 3982, 
NGC 4030, NGC 4038 , NGC 4051, NGC 4088, NGC 4102, NGC 4151

NGC 4192, NGC 4254, NGC 4258, NGC 4321, 
NGC 4388, NGC 4414 , NGC 4438, NGC 4449, NGC 4490, NGC 4501

NGC 4527, NGC 4565, NGC 4568, NGC 4569, 
NGC 4631, NGC 4654 , NGC 4666, NGC 4736, NGC 4984, NGC 5005

NGC 5033, NGC 5055, NGC 5054, NGC 5194, 
NGC 5236, NGC 5248 , NGC 5383, NGC 5457, NGC 5676, NGC 5792


NGC 5907, NGC 6946, NGC 7331, NGC 7479


The distribution of the derived thermal fractions and non-thermal
spectral indices can be seen, here.


The mean value of the thermal fraction at 1 GHz is: 0.08+-0.01


The mean value of the non-thermal spectra lindex is: 0.83+-0.02
 

The separation of thermal fraction and non-thermal spectral index
assumes optically thin emission and a power-law nature of the
synchrotron emission. The last assumption is critical because
synchrotron and inverse-Compton losses steepens the non-thermal 
radio spectrum. 

Therefore, an independent estimate of the thermal fraction is necessary.
This was done using H_alpha fluxes and the synchrotron spectral indices
were recalculated. As one can see there is
good agreement between the two quantities. A more detailed description
of the test can be read in the following paper .


Questions concerning the survey, the results, the overlays etc.
feel free to ask:
Stefan Niklas 
         

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