Matter properties ALFALFA galaxies with TNG100 code

We determined their dark matter content by applying a dynamical method based on HI line widths measured with the curve-of-growth technique, together with inclination corrections inferred from optical images. We built a sample of 2453 gas-rich, predominantly late-type galaxies spanning a stellar mass range of 10^8.7^M_{sun}_ to 10^11.4^M_{sun}_ by matching them one-to-one with their counterparts from the ALFALFA survey and the TNG100 simulation, ensuring a direct match of stellar mass and HI radius.

We generated mock images and mock HI-integrated spectra for TNG100 galaxies, and applied the same dynamical method to both ALFALFA and TNG100 mock galaxies to infer their dark matter masses. Across all stellar mass bins, ALFALFA galaxies exhibit lower median dark matter masses than the mock TNG100 simulation results. In each bin, this offset is driven by a tail of galaxies with comparatively low dark matter content, which becomes more prominent toward higher stellar masses.