Dynamics of Star Formation in Merging Galaxies
Summary
The process of galaxy merging reshapes cosmic structure by driving dramatic changes in the distribution and state of interstellar gas, thereby governing the rates and locations of star formation. Gravitational torques arising during close passages funnel diffuse atomic gas into denser molecular phases, compressing clouds and triggering intense starbursts. The efficiency of this conversion depends on the stage of interaction, with the pericentre passage often marking the peak influx of fuel into central regions. Early tidal encounters can also induce asymmetries in star-forming regions, even before pronounced morphological distortions appear. Simulations reveal that major mergers typically produce short-lived but powerful bursts of star formation, whereas minor mergers and multiple interactions can sustain elevated activity over longer timescales. Feedback from young stars and supernovae then regulates further gas collapse, contributing to a complex interplay between inflows, outflows and chemical enrichment. Observational surveys spanning optical, millimetre and infrared wavelengths have characterised molecular gas fractions, star formation efficiencies and metallicity gradients across merger sequences, underpinning our understanding of how these events drive galaxy evolution. Globally, mergers contribute significantly to the cosmic star formation history, particularly in the early Universe, by building stellar mass, altering morphologies and redistributing angular momentum.
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Dynamics of Star Formation in Merging Galaxies publication trend
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Technical terms
Molecular gas fraction: the ratio of molecular hydrogen mass to a galaxy’s total gas or stellar mass, indicating the principal fuel available for star formation.
Star formation efficiency: the rate of star formation per unit mass of molecular gas, reflecting how effectively gas converts into new stars.
Pericentre: the closest approach of two galaxies during an interaction, often marking the phase of strongest tidal influence and gas inflow.
Tidal torque: gravitational forces exerted during an interaction that redistribute angular momentum and drive gas toward central regions.
H α emission: optical emission line from ionised hydrogen regions, commonly used as a tracer of recent or ongoing star formation.
References
- CO Observations of Early-mid Stage Major Mergers in the MaNGA Survey. The Astrophysical Journal Supplement Series (2024).
- Exploring the Impact of Galactic Interactions and Mergers on the Central Star Formation of APEX/EDGE–CALIFA Galaxies. The Astrophysical Journal (2023).
- One-sided H α excess before the first pericentre passage in galaxy pairs. Monthly Notices of the Royal Astronomical Society: Letters (2024).
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