The VariableTNG project: Mass-dependent regulation of galaxy morphology by baryonic feedback

Galaxy morphology is shaped by both assembly history and baryonic processes, but their relative roles remain uncertain. We used the VariableTNG (VTNG) simulation suite to quantify how systematic variations in baryonic feedback regulate the morphological diversity of galaxies, while keeping the initial conditions fixed. VTNG is a suite of cosmological magnetohydrodynamic simulations performed with the moving-mesh code AREPO , in which eight parameters governing stellar and active galactic nucleus (AGN) feedback are varied. At z=1, we quantified galaxy morphology using the kinematic indicators κ_̊m co and v/σ, together with the structural indicator c/a. We find that baryonic feedback produces substantial morphological diversity even among galaxies with identical large-scale initial conditions. The dominant regulating mechanism depends strongly on stellar mass. For M_* łesssim 10^ 11 ̊m M_⊙ , morphology is primarily controlled by the supernova temperature T_̊m SN: higher T_̊m SN delays early star formation, promotes the build-up of a denser and more rotationally supported gas reservoir, and favours the subsequent growth of stellar discs through in situ star formation. At higher masses, morphology becomes increasingly sensitive to AGN feedback, especially the quasar-mode coupling efficiency ε_̊m f,high. A higher ε_̊m f,high suppresses early black hole growth and thus weakens the later radio-mode feedback that is more directly associated with gas depletion and the destruction of rotational support. The morphology--mass relation is therefore non-monotonic, with maximum rotational support at intermediate stellar masses. Our results show that galaxy morphology responds strongly to mass-dependent feedback pathways under controlled initial conditions. In VTNG, stellar feedback primarily drives the morphological response in lower-mass galaxies, whereas AGN self-regulation and subsequent kinetic feedback become increasingly important at the massive end.