Star Formation Processes in Molecular Environments
Summary
Star formation unfolds within the cold, dense cores of molecular clouds, where gravitational collapse overcomes internal pressure, turbulence and magnetic support. In these regions, gas-phase chemistry and dust shielding enable the formation of molecular hydrogen and a rich inventory of trace species such as HCN and HCO+. As collapse proceeds, protostellar objects drive outflows and jets that inject momentum, heat and turbulence into their surroundings. Ultraviolet radiation and cosmic rays alter chemistry, creating photodissociation regions and enhancing ionisation. Feedback from young stars regulates further collapse and can trigger secondary star‐forming episodes in compressed shells. On galactic scales, the interplay between large-scale dynamics, spiral arms, bars or interactions governs the supply and distribution of molecular gas, setting the overall efficiency and rate of star formation. Chemical diagnostics and isotopic abundances record the cumulative history of stellar processing and inform models of galactic chemical evolution. Together, these processes shape the stellar initial mass function, influence the structure of the interstellar medium and underpin the evolution of galaxies.
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Star Formation Processes in Molecular Environments publication trend
The graph below shows the total number of articles in star formation processes in molecular environments across all publications each year (not limited to Nature Index journals).
Technical terms
Molecular cloud: A cold, dense aggregation of gas and dust where molecular hydrogen forms and stars are born.
Dense gas tracer: A molecular line (e.g. HCN or HCO+) whose critical density makes it sensitive to the highest density regions within molecular clouds.
Isotope ratio: The abundance ratio of two isotopic forms of an element, used to trace nucleosynthetic history and gas mixing.
Photodissociation region: A layer of gas where ultraviolet photons dissociate molecules and heat the gas, influencing its chemistry and emission.
Star formation efficiency (SFE): The fraction of gas mass converted into stars per unit time or per freefall time, indicating how effectively clouds form stars.
Cosmic-ray ionisation rate: The frequency at which cosmic rays ionise molecular gas, affecting chemistry, heating and coupling to magnetic fields.
References
- Subkiloparsec Scaling Relations between Hot Gas, Dense Gas, and Star Formation Rate in Five Nearby Star-forming Galaxies. The Astrophysical Journal Letters (2024).
- The ALCHEMI Atlas: Principal Component Analysis Reveals Starburst Evolution in NGC 253. The Astrophysical Journal Supplement Series (2024).
- Direct measurements of carbon and sulfur isotope ratios in the Milky Way. Astronomy & Astrophysics (2023).
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