Mass Assembly and Star Formation in Galaxies
Summary
The formation and evolution of galaxies are governed by the processes that assemble their mass and regulate the conversion of gas into stars. Over cosmic history, galaxies grow through the accretion of cold gas from the intergalactic medium, mergers with other systems, and in situ star formation. The global star formation rate density rises from the earliest epochs to a peak around redshift two before declining to the present day. This trend reflects the interplay between gas inflow, internal feedback from stellar winds and supernovae, and the energy input from active galactic nuclei. The relation between stellar mass and star formation rate, known as the star-forming main sequence, highlights a degree of self-regulation in typical star-forming galaxies. Meanwhile, a subset of massive systems experience quenching, whereby processes such as black-hole-driven outflows or environmental effects terminate star formation and lead to the emergence of quiescent populations. The galaxy stellar mass function encodes the cumulative outcome of these phenomena, revealing the relative abundance of low-, intermediate- and high-mass systems through time. Recent advances in spectroscopic and imaging capabilities have begun to probe galaxies in the first billion years, uncovering rapid mass assembly and diverse evolutionary pathways that challenge existing theoretical frameworks.
Research from Nature Portfolio
Recent observations with next-generation near-infrared spectroscopy have confirmed the existence of massive, quiescent galaxies at redshift around 4.7, indicating that substantial stellar mass can assemble and quench in less than 1.3 billion years after the Big Bang. These galaxies exhibit stellar masses of several 10^10 solar masses and show evidence of a brief but intense star-forming phase followed by rapid cessation of activity. In another study, integral-field spectroscopy of a post-starburst galaxy at redshift three has revealed fast outflows driven by its central supermassive black hole. The observed gas-outflow rates and velocities comparable to the galaxy escape speed provide direct evidence that active galactic nucleus feedback can eject the cold gas reservoir and suppress further star formation while preserving disc structure. Together, these results demonstrate that both extreme early assembly and energetic feedback processes are integral to shaping the growth and quenching of massive galaxies in the young Universe.
Mass Assembly and Star Formation in Galaxies publication trend
The graph below shows the total number of articles in mass assembly and star formation in galaxies across all publications each year (not limited to Nature Index journals).
Technical terms
Redshift: A measure of the cosmic expansion factor used to estimate the look-back time and distance of astronomical objects.
Quenching: The process by which a galaxy’s star formation is rapidly suppressed or halted.
Galaxy stellar mass function: The number density of galaxies as a function of their stellar mass at a given epoch.
Star-forming main sequence: The tight correlation between stellar mass and star formation rate observed in typical star-forming galaxies.
Active galactic nucleus feedback: The impact of energy and momentum from a galaxy’s central black hole on its interstellar medium.
References
- A massive quiescent galaxy at redshift 4.658. Nature (2023).
- A fast-rotator post-starburst galaxy quenched by supermassive black-hole feedback at z = 3. Nature Astronomy (2024).
- SPITZER BRIGHT, ULTRAVISTA FAINT SOURCES IN COSMOS: THE CONTRIBUTION TO THE OVERALL POPULATION OF MASSIVE GALAXIES AT z = 3–7. The Astrophysical Journal (2015).
- The evolution of the galaxy stellar-mass function over the last 12 billion years from a combination of ground-based and HST surveys. Monthly Notices of the Royal Astronomical Society (2021).
- A surprising abundance of massive quiescent galaxies at 3. Monthly Notices of the Royal Astronomical Society (2023).
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