2020/01/31 by Elia Pizzati, Andrea Ferrara, Andrea Pallottini +4 · 1 citation
Physics and Astronomy · #astro-ph.GA #astro-ph.CO
paper · pdf · doi:10.1093/mnras/staa1163
13 pages, 7 figures; accepted for publication in MNRAS
arxiv created 2020/04/24 · arxiv updated 2020/05/13
Recent stacked ALMA observations have revealed that normal, star-forming galaxies at z≈ 6 are surrounded by extended (≈ 10 kpc) [CII] emitting halos which are not predicted by the most advanced, zoom-in simulations. We present a model in which these halos are the result of supernova-driven cooling outflows. Our model contains two free parameters, the outflow mass loading factor, η, and the parent galaxy dark matter halo circular velocity, vc. The outflow model successfully matches the observed [CII] surface brightness profile if η= 3.20 ± 0.10 and vc = 170 ± 10 \rm km s-1, corresponding to a dynamical mass of ≈ 1011 M_\odot. The predicted outflow rate and velocity range are 128 ± 5 M_\odot \rm yr-1 and 300-500 \rm km s-1, respectively. We conclude that: (a) extended halos can be produced by cooling outflows; (b) the large η value is marginally consistent with starburst-driven outflows, but it might indicate additional energy input from AGN; (c) the presence of [CII] halos requires an ionizing photon escape fraction from galaxies f\rm esc ≪ 1. The model can be readily applied also to individual high-z galaxies, as those observed, e.g., by the ALMA ALPINE survey now becoming available.