27 septembre 2022
Titre: Highlights of the SOFIA Legacy Program FEEDBACK and Future Perspectives on Orion A
Par : Slawa Kabanovic (U. Cologne)
Abstract:
During the FEEDBACK legacy survey, 11 high-mass star-forming regions were observed using the [CII] 158 and [OI] 63 micron lines with the upGREAT receiver on SOFIA. We here present the scientific highlights of the program and give a status report on our ongoing work in Orion A.
One significant focus of FEEDBACK was the exploration of galactic HII region bubbles. Expanding [CII] shells were identified in all sources, and potential driving mechanisms were assessed. Our findings indicate that, in the majority of cases (e.g. RCW120, RCW36, NGC7538), the high-velocity expansion is attributed to the stellar wind from massive stars. Recently, we uncovered signs of cloud destruction due to stellar winds and radiation, quantifying this phenomenon using [CII] in the RCW79 region.
Utilizing a multi-layer radiative transfer model for CO and [CII] emission, coupled with HI self-absorption (HISA) studies, we investigated the RCW 120 bubble. Our study detected significant amounts of cold C+ linked to an extensive HI envelope and revealed that the related molecular cloud exhibits a flattened structure likely originating from a residual filament.
In Cygnus X, we unveiled the highly dynamic interaction of CO-dark gas in the form of atomic flows with a small molecular fraction), using [CII], CO emission and HISA. The cloud formation timescale is only ~1 Myr, consistent with recent simulations of fast, colliding HI flows.
As part of the Orion Legacy project (PI S. Kabanovic), multiple long-time integrations across Orion A were performed, successfully detecting weak [13CII] transition lines. These observations enable the first determination of the local [12CII]/[13CII] abundance ratio and possible fractionation effects directly in different physical conditions in Orion A, such as NGC 1977, M43, and M42.