SOFIA FEEDBACK Survey: PDR Diagnostics of Stellar Feedback in Different Regions of RCW 49

Abstract

We quantified the effects of stellar feedback in RCW 49 by determining the physical conditions in different regions using the [C ii] 158 μm and [O i] 63 μm observations from SOFIA, the 12CO (3–2) observations from APEX, and the H2 line observations from Spitzer telescopes. Large maps of RCW 49 were observed with the SOFIA and APEX telescopes, while the Spitzer observations were only available toward three small areas. From our qualitative analysis, we found that the H2 0–0 S(2) emission line probes denser gas compared to the H2 0–0 S(1) line. In four regions (“northern cloud,” “pillar,” “ridge,” and “shell”), we compared our observations with the updated PDR Toolbox models and derived the integrated far-ultraviolet flux between 6 and 13.6 eV (G 0), H nucleus density (n), temperatures, and pressures. We found the ridge to have the highest G 0 (2.4 × 103 Habing units), while the northern cloud has the lowest G 0 (5 × 102 Habing units). This is a direct consequence of the location of these regions with respect to the Wd2 cluster. The ridge also has a high density (6.4 × 103 cm−3), which is consistent with its ongoing star formation. Among the Spitzer positions, we found the one closest to the Wd2 cluster to be the densest, suggesting an early phase of star formation. Furthermore, the Spitzer position that overlaps with the shell was found to have the highest G 0, and we expect this to be a result of its proximity to an O9V star.

Identifying Physical Structures in Our Galaxy with Gaussian Mixture Models: An Unsupervised Machine Learning Technique

“…The "northern and southern clouds" reported in Figure 7 of Tiwari et al (2021) are identified as the red-colored cluster. The "pillar," which is reported as an independent structure in Tiwari et al (2022), is identified as a part of the southern cloud here (Figure 5). In previous studies (Tiwari et al 2021(Tiwari et al , 2022, the pillar is reported to be most intense in the velocity range of 5-15 km s −1 , which overlaps with the southern cloud (most intense within the velocity range of 2-8 km s −1 ).…”

“…The "pillar," which is reported as an independent structure in Tiwari et al (2022), is identified as a part of the southern cloud here (Figure 5). In previous studies (Tiwari et al 2021(Tiwari et al , 2022, the pillar is reported to be most intense in the velocity range of 5-15 km s −1 , which overlaps with the southern cloud (most intense within the velocity range of 2-8 km s −1 ). Morphologically, this pillar can be recognized as a separate structure, but kinematically, it is part of the southern cloud.…”

“…Similar to RCW 120, we excluded five that corresponded to noise and were mainly localized on the edges of the map. Observational studies (Furukawa et al 2009;Tiwari et al 2021Tiwari et al , 2022 identified four different physical structures in RCW 49. We identify three of these.…”

“…The stellar winds of the Wd2 cluster and WR20a have swept up a shell of radius 6 pc which expands at a speed of ∼13 km s −1 and has a mass of 2.5 × 10 4 M e . Besides the shell, this region also hosts two large-scale molecular clouds whose collision led to the formation of the Wd2 cluster (Furukawa et al 2009), namely the ridge and the northern and southern clouds (Tiwari et al 2021(Tiwari et al , 2022.…”

“…These structures can be spatially and spectrally distinct. Their physical conditions are among others dependent on morphology, relative location to the main ionizing source and the star formation history of the region (Tiwari et al 2022). Estimations of these physical conditions quantify the role of stellar feedback in the evolution of the ISM.…”