Abstract

Contributed Talk - Splinter GalaxyEvol

Thursday, 12 September 2024, 14:48   (S21)

Complex gas distribution in the Extended [CII] and CO (3→2) Maps of the M17 nebula

Parit Mehta, Jürgen Stutzki, Slawa Kabanovic, Robert Simon, Cristian Guevara, Nicola Schneider, Rolf Güsten
Institute for Astrophysics, University of Cologne/Max-Planck-Institut für Radioastronomie, Bonn

M17 is one of the most massive star forming regions (SFR) in our galaxy: a young stellar nursery with over 100 OB stars embedded in dense gas, illuminating two prominent Photon Dominated Regions (PDRs), the M17-North (M17-N) and M17-South West (M17-SW). Along with its central cluster, NGC 6618, M17 has been studied extensively with a large amount of data available in the literature for CO and other molecular lines, dust, as well as data from other wavelength regimes. We present a new large-scale map of velocity-resolved [CII] 158μm emission across an area of approx. 11x12 pc2 towards the M17 nebula as part of the SOFIA FEEDBACK legacy program, along with complementary [OI] 63μm, CO 3-2 and other lines towards M17. The high spatial and spectral resolution, along with efficient large-scale mapping capabilities offered by upGREAT on- board SOFIA in [CII] reveal for the first time the complex structure of the extended [CII] emission in unprecedented detail. High optical depths and self-absorption of [CII] were confirmed by Guevara et al. (2020), pointing to the possible existence of a cold absorbing foreground in front of the warm PDR background layer. Through appropriate averaging of SOFIA/upGREAT [CII] data and through Gaussian Mixture Model-based clustering of spectra, we are able to achieve good S/N, revealing the fainter spectral signature of the outer [13CII] hyperfine satellites over large parts of the map. The abundance-ratio-scaled [13CII] profiles are comparatively much brighter compared to [12CII] towards the M17-SW, but also significantly so in the M17-N and in outer areas that surround the PDRs. We derive physical conditions and spatial variations of the warm background and cold foreground [CII] emission for each cluster of spectra, in comparison with CO (3→2) line emission, and discuss implications for interpretation of [CII] intensities in galactic and extra-galactic SFRs.