Galactic outflow and diffuse gas properties at z>=1 using different baryonic feedback models

TL;DR

This study uses cosmological simulations with a novel feedback model to analyze galactic outflows at redshifts 1 to 5, revealing how outflow properties relate to galaxy mass and star formation rate, and comparing different feedback models.

Contribution

Introduces the MUPPI sub-resolution model that derives outflow properties from local gas conditions, providing more realistic outflow simulations compared to traditional models.

Findings

Outflow velocity and rate increase with galaxy mass and SFR.

The outflow mass loading factor varies between 0.2 and 10.

MUPPI produces outflows with properties matching observations.

Abstract

We measure and quantify properties of galactic outflows and diffuse gas at $z \geq 1$ in cosmological hydrodynamical simulations. Our novel sub-resolution model, MUPPI, implements supernova feedback using fully local gas properties, where the wind velocity and mass loading are not given as input. We find the following trends at $z = 2$ by analysing central galaxies having a stellar mass higher than $10^{9} M_{\odot}$. The outflow velocity and mass outflow rate ($\dot{M}_{\rm out}$) exhibit positive correlations with galaxy mass and with the star formation rate (SFR). However, most of the relations present a large scatter. The outflow mass loading factor ($\eta$) is between $0.2 - 10$. The comparison Effective model generates a constant outflow velocity, and a negative correlation of $\eta$ with halo mass. The number fraction of galaxies where outflow is detected decreases at lower redshifts, but remains more than $80 \%$ over $z = 1 - 5$. High SF activity at $z \sim 2 - 4$ drives strong outflows, causing the positive and steep correlations of velocity and $\dot{M}_{\rm out}$ with SFR. The outflow velocity correlation with SFR becomes flatter at $z = 1$, and $\eta$ displays a negative correlation with halo mass in massive galaxies. Our study demonstrates that both the MUPPI and Effective models produce significant outflows at $\sim 1 / 10$ of the virial radius; at the same time shows that the properties of outflows generated can be different from the input speed and mass loading in the Effective model. Our MUPPI model, using local properties of gas in the sub-resolution recipe, is able to develop galactic outflows whose properties correlate with global galaxy properties, and consistent with observations.