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Arxiv: JWST Observations of Starbursts: Cold Clouds and Plumes Launching in the M82 Outflow Published: 5/6/2024 8:57:58 PM Updated: 5/6/2024 8:57:58 PM

Paper abstract: In this paper we study the filamentary substructure of 3.3 \mum PAHemission from JWST/NIRCam observations in the base of the M82 star-burst drivenwind. We identify plume-like substructure within the PAH emission with widthsof ~50 pc. Several of the plumes extend to the edge of the field-of-view,and thus are at least 200-300 pc in length. In this region of the outflow, thevast majority (~70\%) of PAH emission is associated with the plumes. Weshow that those structures contain smaller scale "clouds" with widths that are~5-15 pc, and they are morphologically similar to the results of"cloud-crushing" simulations. We estimate the cloud-crushing time-scales of~0.5-3 Myr, depending on assumptions. We show this time scale isconsistent with a picture in which these observed PAH clouds survived break-outfrom the disk rather than being destroyed by the hot wind. The PAH emission inboth the midplane and the outflow is shown to tightly correlate with that ofPa\alpha emission (from HST/NICMOS data), at the scale of both plumes andclouds, though the ratio of PAH-to-Pa\alpha increases at further distancesfrom the midplane. Finally, we show that the outflow PAH emission is suppressedin regions of the M82 wind that are bright in X-ray emission. Overall, ourresults are broadly consistent with a picture in which cold gas in galacticoutflows is launched via hierarchically structured plumes, and those smallscale clouds are more likely to survive the wind environment when collectedinto the larger plume structure.