Understanding galaxy formation and evolution through kinematics and interstellar medium properties

Abstract

We study the kinematics and ISM properties of galaxies and how external and internal mechanisms influence their evolution. We start by connecting the rotational motion of galaxies to their large-scale environment. We then examine the turbulent motion of gas in galaxies. Finally, we measure the metal content within galaxies. To understand the build-up of galaxy stellar angular momentum, we study the coherence between the spin vectors and the motion of neighbouring galaxies using data from the SAMI Survey. We find modest evidence of coherence signals (~2sigma) for neighbouring galaxies within 2 Mpc, i.e. the rotation of a galaxy is aligned with the average motion of neighbouring galaxies. However, the coherence signals are consistent with zero or negative for neighbours outside 3 Mpc, suggesting the positive signals we observed within 2 Mpc may be due to coincidental scatter or variance of largescale structure. We then analyse the gas kinematics of the galaxies at z~0.3 using data from the MAGPI survey. The average ionised gas velocity dispersion (sigma_gas) of galaxies at z~0.3 is 26.1 km/s. We compare our results to the SAMI(z~0) and KROSS(z~1) surveys. We find that the average sigma_gas is similar at the same SFR surface density (Sigma_SFR) for the SAMI, MAGPI and KROSS galaxies, and Sigma_SFR has the strongest correlation with sigma_gas. This correlation suggests that the mechanisms related to Sigma_SFR, such as stellar feedback, may be the dominant drivers of gas turbulence from z~1 to z~0. We extend our analysis of the gas distribution to measure the metallicity gradient of MAGPI galaxies. The median of the metallicity gradient is -0.028 dex/kpc. The metallicity gradient has significant positive correlations with sigma_gas and Sigma_SFR. Galaxies with stronger gas turbulence have flatter metallicity gradients, suggesting that stellar feedback, gas accretion and transportation drive gas turbulence and enhance gas mixing, which flattens the metallicity gradients.