  The origin of the tight radio--IR correlation in galaxies has not been fully
understood. One reason is the uncertainty about which heating sources (stars or
diffuse interstellar radiation field)provide the energy that is absorbed by
dust and re-radiated in IR. Another problem is caused by comparing the IR
emission with the thermal and nonthermal components of the radio continuum
emission separated by simplistically assuming a constant nonthermal spectral
index. We use the data at the $Spitzer$ MIPS wavelengths of 24, 70, and 160
$\mu$m, as well as recent radio continuum map at 3.6 cm observed with the
100--m Effelsberg telescope. Using the wavelet transformation, we separate
diffuse emission components from compact sources and study the radio-IR
correlation at various scales. We also investigate the IR correlations with the
thermal and nonthermal radio emissions separated by our developed method. A
H$\alpha$ map serves as a tracer of star forming regions.
