Cooling flows as a reference solution for the hot circumgalactic medium

The circumgalactic medium (Formula presented) haloes is dominated by a hot phase ((Formula presented)). While many models exist for the hot gas structure, there is as yet no consensus. We compare cooling flow models, in which the hot CGM flows inwards due to radiative cooling, to the (Formula presented) haloes in galaxy formation simulations from the Feedback in Realistic Environments (FIRE) project at (Formula presented). The simulations include realistic cosmological evolution and feedback from stars but neglect AGN feedback. At both mass scales, CGM inflows are typically dominated by the hot phase rather than by the ‘precipitation’ of cold gas. Despite being highly idealized, we find that cooling flows describe (Formula presented) haloes very well, with median agreement in the density and temperature profiles of ∼ 20 and ∼ 10 per cent, respectively. This indicates that stellar feedback has little impact on CGM scales in those haloes. For ~10¹² M_☉ haloes, the thermodynamic profiles are also accurately reproduced in the outer CGM. For some of these lower-mass haloes, cooling flows significantly overpredict the hot gas density in the inner CGM. This could be due to multidimensional angular momentum effects not well captured by our one-dimensional cooling flow models and/or to the larger cold gas fractions in these regions. Turbulence, which contributes ∼ 10–40 of the total pressure, must be included to accurately reproduce the temperature profiles. Overall, cooling flows predict entropy profiles in better agreement with the FIRE simulations than other idealized models in the literature.