Evolution of cold streams in hot gaseous halos

In the prevailing model of galaxy formation and evolution, the process of gas accretion onto central galaxies undergoes a transition from cold-dominated to hot-dominated modes. This shift occurs when the mass of the parent dark matter halos exceeds a critical threshold known as Mshock. Moreover, cold gas usually flows onto central galaxies through filamentary structures, currently referred to as cold streams. However, the evolution of cold streams in halos with masses around Mshock, particularly how they are disrupted, remains unclear. To address this issue, we conduct a set of idealised hydrodynamic simulations. Our simulations show that (1) for a gas metallicity Z=0.001-0.1Z_, cold stream with an inflow rate ~ 3\, M_/yr per each can persist and effectively transport cold and cool gas to the central region ($< 0.2$ virial radius) in halos with mass 10¹²\, M_, but is disrupted at a radius around $0.2$ virial radius due to compression heating for halos with mass 3 × 10¹²\, M_. (2) At z~ 2, the maximum halo mass that capable of hosting and sustaining cold streams Mₛₜᵣₑₐₘ is between 1× 10¹² M_ and 1.5× 10¹²M_ for gas metallicity Z=0.001Z_, while for a higher gas metallicity Z=0.1Z_, this value increases to ~ 1.5× 10¹²M_. (3) The evolution and ultimate fate of cold streams are determined primarily by the rivalry between radiative cooling and compression. Stronger heating due to compression in halos more massive than Mₛₜᵣₑₐₘ can surpass cooling and heat the gas in cold streams to the hot (≥ 10⁶\, K) phase.