Thermal re-emission in some selected quiescent Bok globules CB4, CB170, CB175 and CB181

The emission flux values as observed for different IRAS band pairs often do not give rise to a single black body temperature for the dust particles present in Bok globules. In a quiescent cloud, the dust particles should be heated by the background interstellar radiation field (ISRF) to attain equilibrium temperature, and we expect the different band pairs to result in a single blackbody temperature. To explain this anomaly, we propose a model in which the dust temperature variations are attributed to the presence of two distinct dust populations: modified hydrogenated amorphous hydrocarbon (mHAC) and amorphous pyroxene. This study focuses on four selected small, compact, quiescent clouds (Bok globules), namely CB4, CB170, CB175, and CB181, which exhibit no star formation, making them ideal for our analysis. The dust temperature (Td) is determined by considering the ISRF's effect on these dust populations. The observed higher dust temperatures deduced from the short wavelength flux pair ratio ‘F12/F25’ and the colder temperatures deduced from the long wavelength flux pair ratio 'F60/F100' can be assigned to the presence of two dust populations: mHAC and amorphous pyroxene. To accurately model the observed flux ratios, a weighting factor 'ω' was introduced, representing the relative contribution of pyroxene dust flux to that of mHAC particles. Analysis across four Bok globules revealed that this weighting factor lies within the range of 8 × 10^4 to 2 × 10^5. Thus, the different temperatures observed in the various IRAS bands can be coherently explained by considering properties of these two dust populations.