The redshift evolution of the baryonic Tully-Fisher relation in Simba

TL;DR

This study uses the Simba simulation to predict how the baryonic Tully-Fisher relation evolves with redshift, providing insights for upcoming LADUMA survey observations and methods to estimate dark matter halo mass from HI spectral lines.

Contribution

It offers the first detailed predictions of the redshift evolution of the BTFR using Simba, including the effectiveness of HI spectral line widths in measuring galaxy dynamics at different redshifts.

Findings

W20 spectral line widths show lower scatter and more pronounced evolution than W50.

LADUMA can detect weak redshift evolution of the BTFR with auxiliary data.

Weak evolution observed between rotational velocity and dark matter halo mass.

Abstract

The baryonic Tully-Fisher relation (BTFR) is an important tool for constraining galaxy evolution models. As 21-cm HI emission studies have been largely restricted to low redshifts, the redshift evolution of the BTFR is less studied. The upcoming LADUMA survey (Looking At the Distant Universe with the MeerKAT Array) will address this. As preparation for LADUMA, we use the Simba hydrodynamical galaxy formation simulation from the Simba-hires (25 h$^{-1}$ Mpc)$^{3}$ run to generate rotational velocity measures from galaxy rotation curves ($V_{\rm flat}$) and HI spectral line profile widths ($W_{\rm 50}$ and $W_{\rm 20}$) at three different redshifts ($z$ = 0, 0.5, and 1). Using these measures, together with the dark matter velocity dispersion and halo mass, we consider the redshift evolution of the BTFR of Simba galaxies. We find that LADUMA will be successful in detecting weak redshift evolution of the BTFR, provided that auxiliary data is used to distinguish galaxies with disky morphologies. $W_{\rm 20}$ spectral line widths give lower scatter and more pronounced redshift evolution compared to $W_{\rm 50}$. We also compare these rotational velocity measures to the dark matter velocity dispersion across redshift and galaxy morphology. We find weak redshift evolution between rotational velocity and the dark matter halo mass, and provide fits for estimating a galaxy's dark matter halo mass from HI spectral line widths. This study with Simba showcases the importance of upcoming, deep SKA pathfinder surveys such as LADUMA, and provides predictions to compare with redshift evolution of the BTFR and galaxy dark matter content from HI rotational velocity measures.