The SOFIA FEEDBACK Legacy Survey Dynamics and Mass Ejection in the Bipolar H ii Region RCW 36

Abstract

We present [C ii] 158 μm and [O i] 63 μm observations of the bipolar H ii region RCW 36 in the Vela C molecular cloud, obtained within the SOFIA legacy project FEEDBACK, which is complemented with APEX 12/13CO (3–2) and Chandra X-ray (0.5–7 keV) data. This shows that the molecular ring, forming the waist of the bipolar nebula, expands with a velocity of 1–1.9 km s−1. We also observe an increased line width in the ring, indicating that turbulence is driven by energy injection from the stellar feedback. The bipolar cavity hosts blueshifted expanding [C ii] shells at 5.2 ± 0.5 ± 0.5 km s−1 (statistical and systematic uncertainty), which indicates that expansion out of the dense gas happens nonuniformly and that the observed bipolar phase might be relatively short (∼0.2 Myr). The X-ray observations show diffuse emission that traces a hot plasma, created by stellar winds, in and around RCW 36. At least 50% of the stellar wind energy is missing in RCW 36. This is likely due to leakage that is clearing even larger cavities around the bipolar RCW 36 region. Lastly, the cavities host high-velocity wings in [C ii], which indicates relatively high mass ejection rates (∼5 × 10−4 M ⊙ yr−1). This could be driven by stellar winds and/or radiation but remains difficult to constrain. This local mass ejection, which can remove all mass within 1 pc of RCW 36 in 1–2 Myr, and the large-scale clearing of ambient gas in the Vela C cloud indicate that stellar feedback plays a significant role in suppressing the star formation efficiency.

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

“…We can see that the turbulent pressures are higher than the thermal pressures and thus dominate the dynamics of the gas in all regions of RCW 49. This is similar to the findings toward the stellar-feedback-driven shells of RCW 49 and RCW 36 (Tiwari et al 2021;Bonne et al 2022). When comparing the p th and p turb values derived for the shell in this work with those from Tiwari et al (2021), we find that the values estimated here are lower by up to a factor of ∼1.6.…”

JCMT BISTRO Observations: Magnetic Field Morphology of Bubbles Associated with NGC 6334

“…For instance, studies (e.g., Chen et al 2022) indicate that HII regions may be elongated along the initial orientation of the field lines as expansion perpendicular to the field lines is met with resistance. Bonne et al (2022) suggested that the initial magnetic field orientation may have also enforced the orientation of bipolar cavities in the Vela C cloud. We note that the elliptical elongations of the NGC 6334 bubbles are reported in the MIR observations of Simpson et al (2012), but they are very small, except for S2-a, as illustrated in Figure 16 where the elongation of the bubble is not completely aligned with the large-scale magnetic fields (Chen et al 2022).…”

The PhotoDissociation Region Toolbox: Software and Models for Astrophysical Analysis

“…We will provide a series of models that cover the metallicity range 0.03-5 while accounting for the expected scaling in dust and metals. It has become increasingly apparent that the [O I] 63 μm, and [C II] 158 μm lines can be self-absorbed, thereby affecting the interpretation of the integrated line intensities (Bonne et al 2022;Goldsmith et al 2021;Graf et al 2012;Guevara et al 2020;Kabanovic et al 2022). This is most often noticed by a [O I] 145 μm/63 μm ratio greater than 0.1 or a central dip in velocity-resolved profiles seen in one isotope but not another (e.g., [ 12 C II] versus [ 13 C II]).…”