Strong Correlation Between Galactic H <scp>I</scp>-to-stellar Mass Ratio and Halo Spin Explored by H <scp>I</scp>-rich Galaxies

Abstract Using a semi-analytic approach, we estimate halo spins for a large sample of H I -rich galaxies from the Arecibo Legacy Fast ALFA Survey and examine the correlation between H I mass fractions and halo spins. Our analysis reveals a strong correlation between halo spin and the H I -to-stellar mass ratio in both low-mass and massive galaxy samples. This finding suggests a universal formation scenario: higher halo spin reduces angular momentum loss and gas condensation, leading to lower star formation rates and weaker feedback, which in turn help retain gas within dark matter halos.