2013A&A...559A..81X

Radio continuum observations detect non-thermal synchrotron and thermal bremsstrahlung radiation. Separation of the two different emission components is crucial for studying the properties of the Galactic 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 (SNRs) are expected to be discovered. We aim to develop a method that 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 SNRs in the complex. Multi-frequency radio continuum data from large-scale surveys were used to develop a new component-separation method. Spectral analysis was done pixel-by-pixel for the non-thermal synchrotron emission with a realistic spectral index distribution and a fixed spectral index of β=-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 9.5'. The thermal emission component is found to comprise 75% of the total continuum radiation at λ6cm. 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 100mK*T_b is found. We successfully make the large-extent known SNRs and the HII regions embedded in the complex standing out, but no new large SNRs brighter than ∑_1GHz=3.7x10^–21W/m²/Hz/sr are found.