2020A&A...644A..46K

Aims. We investigate the role of selective dissociation in the process of star formation by comparing the physical parameters of protostellar-prestellar cores and the selected regions with the CO isotope distributions in photo-dissociation regions. We seek to understand whether there is a better connection between the evolutionary age of star forming regions and the effect of selective dissociation
Methods. We used wide-field observations of the ¹²CO, ¹³CO, and C¹⁸O (J=1-0) emission lines to study the ongoing star formation activity in the Aquila molecular region, and we used the 70 and 250µm data to describe the heating of the surrounding material and as an indicator of the evolutionary age of the core.
Results. The protostellar-prestellar cores are found at locations with the highest C¹⁸O column densities and their increasing evolutionary age coincides with an increasing 70µm/250µm emission ratio at their location. The evolutionary age of the cores may also follow from the ¹³CO versus C¹⁸O abundance ratio, which decreases with increasing C¹⁸O column densities. The original mass has been estimated for nine representative star formation regions and the original mass of the region correlates well with the integrated 70µm flux density. Similarly, the X13^CO/X_C18^O_ ratio, which provides the dissociation rate for these regions correlates with the 70µm/250µm flux density ratio and reflects the evolutionary age of the star formation activity.