Statistical Properties of Cold Streams In Massive Star-Forming Halos in TNG50

TL;DR

This study analyzes the prevalence and properties of cold gas streams in massive halos from z=4 to 0 using TNG50 simulations, revealing their significant role at cosmic noon and their disruption at later times.

Contribution

Introduces a novel algorithm to detect and characterize cold streams in simulated halos, providing new insights into their evolution and impact on galaxy fueling.

Findings

Cold streams are present in over 80% of massive halos at z=2-1.

Streams often form co-planar, three-stream configurations at peak prevalence.

Streams typically disrupt before reaching the galaxy center, affecting mass inflow.

Abstract

Cold, dense streams of gas are predicted to penetrate deeply into massive halos (> 10^12 Msun) at cosmic noon (z=4-2), fueling galaxies to sustain high star formation rates. We investigate the prevalence of such cold streams in TNG50 over the range z=4-0, using a novel algorithm to automatically detect cold streams in simulated halos. We qualitatively and quantitatively characterize the geometric and physical properties of the detected streams over cosmic time. We find that cold streams are ubiquitous in massive halos at cosmic noon, occurring in more than 80 percent of such systems down to z=1, before becoming rare by z=0. At their peak prevalence (z=2-1), streams are often found in roughly co-planar, three-stream configurations. These streams generally exhibit a dense and cool core, surrounded by a diffuse and warmer envelope. However, we find that in TNG50, these streams typically disrupt in the outer halo and do not penetrate efficiently to the central galaxy, with the total mass inflow from streams peaking at z=2. Our results underscore the importance of cold streams in fueling galaxies at early times, but they highlight the need for higher-resolution simulations to fully capture their survival and impact at later epochs. Future cosmological zoom-in simulations, with better resolution in the CGM, will be essential to resolve turbulent mixing layers and feedback-inflow interactions that determine whether cold streams can reach the galactic disk.