Thermal and non-thermal emission in the Cygnus X region
  Radio continuum observations detect non-thermal synchrotron and thermal
bremsstrahlung radiation. Separation of the two different emission components
is crucial to study the properties of diffuse interstellar medium. The Cygnus X
region is one of the most complex areas in the radio sky which contains a
number of massive stars and HII regions on the diffuse thermal and non-thermal
background. More supernova remnants are expected to be discovered. We aim to
develop a method which can properly separate the non-thermal and thermal radio
continuum emission and apply it to the Cygnus X region. The result can be used
to study the properties of different emission components and search for new
supernova remnants in the complex. Multi-frequency radio continuum data from
large-scale surveys are used to develop a new component separation method.
Spectral analysis is done pixel by pixel for the non-thermal synchrotron
emission with a realistic spectral index distribution and a fixed spectral
index of beta = -2.1 for the thermal bremsstrahlung emission. With the new
method, we separate the non-thermal and thermal components of the Cygnus X
region at an angular resolution of 9.5arcmin. The thermal emission component is
found to comprise 75% of the total continuum emission at 6cm. Thermal diffuse
emission, rather than the discrete HII regions, is found to be the major
contributor to the entire thermal budget. A smooth non-thermal emission
background of 100 mK Tb is found. We successfully make the large-extent known
supernova remnants and the HII regions embedded in the complex standing out,
but no new large SNRs brighter than Sigma_1GHz = 3.7 x 10^-21 W m^-2 Hz^-1
sr^-1 are found.
