http://arxiv.org/abs/1910.14235
Feedback is indispensable in galaxy formation. However, cosmological simulations often use \textit{ad hoc} feedback recipes due to a lack of resolution. Conversely, small-box simulations, while better resolving the feedback process, cannot capture gas evolution beyond the simulation domain. We aim to bridge the gap by implementing small-box results of SNe-driven outflows into a Mpc simulation and studying their impact on large scales. Small-box simulations show that the outflows are multiphase, but the hot phase (T$\approx$ 10$^{6-7}$ K) carries the majority of energy and metals. We implement the hot outflows at the base of a Milky Way-mass galaxy, and examine how they impact the circumgalactic medium (CGM). In this paper, we discuss the case when the hot outflows are gravitationally bound by the dark matter halo. We find that outflows form a large-scale, metal-enriched atmosphere with fountain motions. As more hot gas accumulates, the inner atmosphere becomes “saturated”. Cool clumps condense and fall toward the galaxy; the rate of condensation balances the injection of the hot outflows. This balance leads to a universal density profile of the hot atmosphere, independent of the outflow mass flux. The atmosphere has a radially-decreasing temperature, which naturally produces the observed X-ray luminosity and column densities of O VI, O VII, O VIII of the CGM around Milky Way-like galaxies. The self-regulated atmosphere has a baryon and a metal mass of $(0.5-1.2)\times 10^{10}M_\odot$ and $(0.6-1.4)\times 10^8 M_\odot$, respectively, small compared to the “missing” baryons and metals from the halo. We conjecture that the missing materials reside at even larger radii, ejected by more powerful outflows in the past.
M. Li and S. Tonnesen
Fri, 1 Nov 19
45/54
Comments: 26 pages, 18 pages, submitted to ApJ