In this talk, I present a systematic study of how galaxy morphology connects to dark matter halo properties, using IllustrisTNG-50/100 simulations. The presentation is structured into two related parts.
First, I will introduce a novel kinematic decomposition method that improves on existing ones with a more physical approach to identifying morphological components. I find the circularity threshold defining thin discs depends on halo conditions. Applying this method to TNG50, I revisit the question which halo structural parameters constitute the best predictor for disc size and show that halo spin, concentration, and accretion rate all influence it at fixed halo mass—challenging semi-analytical models that rely only on spin. Employing Random Forest and Symbolic Regression, I build empirical relations to predict galaxy morphology from halo properties, with preliminary results for disc mass, size and height.
Second, I study a new category of extreme galaxies revealed by JWST – giant bulgeless discs (GBDs) at high-z. Using our decomposition method, I identify GBD analogs in TNG100 and analyze their halo and environmental conditions. The results from mock images and related measurements reveal that GBDs form in young cosmic knots, populating host halos of high spin, low concentration, and spherical shapes - in line with our insights of disc-halo connections in Part I. They feature dynamically coherent circum-galactic medium, as well as gas-rich, coherent mergers, which preserve their disc morphology and drive their large sizes. Interestingly, all the simulated GBDs harbor a compact, aligned inner disc, marginally resolvable in JWST images with a Sersic index near unity.
Also check out other Workshops in Hong Kong.
