High resolution LAsMA 12CO and 13CO observation of the G305 giant molecular cloud complex. II. Effect of feedback on clump properties

Context. Understanding the effect of feedback from young massive stars on the star forming ability of their parental molecular clouds is of central importance for studies of the interstellar medium and star formation. Aims. We observed the G305 star-forming complex in the J = 3-2 lines of CO and CO to investigate whether feedback from the central OB stars were triggering star formation in G305 or actually disrupting this process. Methods. The region was decomposed into clumps using dendrogram analysis. A catalog of the clump properties such as their positions, luminosities, masses, radii, velocity dispersions, volume densities, surface mass densities, etc. was created. The surface mass densities of the clumps were plotted as a function of the incident 8 μm flux. A mask of the region with 8 μm flux > 100 MJy/sr was created and clumps were categorized into three classes based on their extent of overlap with the mask, namely “mostly inside” (>67% overlap), “partly inside” (>10% and <67% overlap), and “outside” (<10% overlap). The surface mass density distribution of each of these populations was separately plotted. This was followed by comparing the G305 clumps with the Galactic average taken from a distance limited sample of ATLASGAL and CHIMPS clumps. Finally, the cumulative distribution functions (CDF) of the clump masses in G305 and their L/M ratios were compared to that of the Galactic sample to determine which mechanism of feedback was dominant in G305. Results. The surface mass densities of clumps showed a positive correlation with the incident 8 μm flux. The data did not have sufficient velocity resolution to discern the effects of feedback on the linewidths of the clumps. The sub-sample of clumps named “mostly inside” had the highest median surface mass densities followed by the “partly inside” and “outside” sub-samples. The difference between the surface mass density distribution of the three sub-samples were shown to be statistically significant using the KS test. The “mostly inside” sample also showed the highest level of fragmentation compared to the other two sub-samples. These prove that the clumps inside the G305 region are triggered. The G305 clump population is also statistically different from the Galactic average population, the latter approximating that of a quiescent population of clumps. This provided further evidence that redistribution was not a likely consequence of feedback on the GMC. The CDFs of clump masses and their L/M ratios are both flatter than that of the Galactic average, indicating that clumps are heavier and more efficient at forming stars in G305 compared to the Galactic average. Conclusions. Feedback in G305 has triggered star formation. The collect and collapse method is the dominant mechanism at play in G305.