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Collision between molecular clouds IV: The role of feedback and magnetic field in head on collisions

We systematically investigate how cloud-cloud collisions influence star formation, emphasizing the roles of collision velocity, magnetic field orientation, and radiative feedback. Using the first cloud-cloud collision simulations that model individual star formation and accretion with all stellar feedback mechanisms, we explore the morphological evolution, star formation efficiency (SFE), fragmentation, stellar mass distribution, and feedback-driven gas dispersal. Our results show that cloud collisions substantially enhance the rate and timing of star formation compared to isolated scenarios, though the final SFE remains broadly similar across all setups. Lower collision velocities facilitate prolonged gravitational interaction and accumulation of gas, promoting sustained star formation characterized by elongated filamentary structures. Conversely, high-velocity collisions induce rapid gas compression and turbulent motions, leading to intense but transient episodes of star formation, which are curtailed by feedback-driven dispersal. The orientation of the magnetic field markedly affects collision outcomes. Parallel fields allow gas to collapse efficiently along magnetic lines, forming fewer but more massive stars. In contrast, perpendicular fields generate significant magnetic pressure, which stabilizes the shock-compressed gas and delays gravitational collapse, resulting in more distributed and less massive stellar fragments. Radiative feedback from massive stars consistently regulates star formation, halting further gas accretion at moderate efficiencies (10-15%) and initiating feedback-driven dispersal. Although the cloud dynamics vary significantly, the stellar mass function remains robust across scenarios-shaped modestly by magnetic orientation but only weakly influenced by collision velocity.