Stellar Dynamics and Star Formation in Galaxies and Molecular Clouds

Galaxies evolve through a complex interplay between the gravitational motions of stars, the behaviour of the interstellar medium (ISM) and the processes that govern the collapse of cold gas into new stars. Stellar dynamics—from the rotation of discs to the random motions in bulges and haloes—shapes the global structure and stability of galaxies. In parallel, molecular clouds, the dense and cold constituents of the ISM, provide the raw material for star formation. Within these clouds, the microphysics of molecular hydrogen formation, dust cooling and turbulence set the efficiency and timescale of collapse. Feedback from supernovae, young massive stars and accreting black holes can inject energy and momentum, regulating gas inflow and quenching or sustaining star formation. Observations across the electromagnetic spectrum, complemented by high-resolution simulations, have revealed patterns of inside-out growth and downsizing, cloud–cloud collisions that spark clusters, and the central role of dust-grain catalysis in H₂ formation. Together, these strands forge a coherent picture of how galaxies assemble their stellar mass over cosmic time and how dense molecular regions within them give birth to stars.

Research from Nature Portfolio

Recent studies have revealed that supermassive black holes exert a decisive influence on the cool gas reservoirs of massive galaxies, with the ratio of atomic hydrogen to stellar mass showing a stronger correlation with black hole mass than with any other galactic parameter. This finding points to accretion-driven feedback as the primary regulator of cold gas content and star formation. At the molecular cloud scale, laboratory and theoretical investigations demonstrate that carbonaceous dust grains sustain highly efficient formation of molecular hydrogen on their surfaces at temperatures up to around 250 K. This breakthrough reshapes our understanding of H₂ availability and cooling in both local and high-redshift environments, indicating that warm dust contributes substantially to the onset of cloud collapse and star formation across a broad range of interstellar conditions.

Stellar Dynamics and Star Formation in Galaxies and Molecular Clouds publication trend

The graph below shows the total number of articles in stellar dynamics and star formation in galaxies and molecular clouds across all publications each year (not limited to Nature Index journals).

Technical terms

Stellar dynamics: the study of motions and gravitational interactions of stars within galaxies or clusters.

Interstellar medium (ISM): gas and dust filling the space between stars, comprising various phases from hot plasma to cold molecular gas.

Molecular cloud: a dense, cold region of the ISM where molecules, primarily H₂, form and collapse to form stars.

Black hole feedback: energy and momentum released by accreting black holes into surrounding gas, influencing star formation rates.

Inside-out growth: a pattern of galaxy assembly in which central regions form stars earlier than the outskirts.

H₂ formation efficiency: rate at which atomic hydrogen recombines into molecular form on dust grain surfaces, governing cooling and collapse of clouds.

Cloud–cloud collision: an interaction between two molecular cloud complexes that can compress gas and trigger rapid star or cluster formation.

References

1. Black holes regulate cool gas accretion in massive galaxies. Nature (2024).
2. Enhanced star formation through the high-temperature formation of H2 on carbonaceous dust grains. Nature Astronomy (2023).
3. Quiescent Low-mass Galaxies Observed by JWST in the Epoch of Reionization. The Astrophysical Journal Letters (2023).
4. Resolved stellar population properties of PHANGS-MUSE galaxies. Astronomy & Astrophysics (2023).
5. MOLECULAR CLOUDS TOWARD THE SUPER STAR CLUSTER NGC 3603; POSSIBLE EVIDENCE FOR A CLOUD–CLOUD COLLISION IN TRIGGERING THE CLUSTER FORMATION. The Astrophysical Journal (2013).