Study Ties Galaxy Growth Shutdown to 10^12.5-Solar-Mass Hot Halo Threshold
Updated
Updated · Space.com · Jun 9
Study Ties Galaxy Growth Shutdown to 10^12.5-Solar-Mass Hot Halo Threshold
1 articles · Updated · Space.com · Jun 9
Summary
A new paper led by Preetish Mishra argues galaxies sharply lose star-forming efficiency once they reach about 10^12.5 solar masses, when a stable hot gas halo forms and cuts off fresh fuel.
Using the Horizon Run 5 cosmological simulation, the team tracked roughly 20,000 massive central galaxies and found the stellar-to-total mass ratio peaks at 10^12.4 to 10^12.7 solar masses.
Above that range, star-formation efficiency drops by more than a factor of three because infalling gas is shock-heated and can no longer cool fast enough to feed new stars for billions of years.
The analysis found bound baryon content varies by no more than 30%, weakening the rival idea that stronger outflows from supernovas or active galactic nuclei drive the slowdown.
The result still depends on simulation physics and only covers galaxies above 10^10.8 solar masses, but the proposed mechanism can be tested with future surveys of clusters and intergalactic gas.
Is there a universal 'off switch' for star formation, or does the cause change with cosmic time?
Can the James Webb Telescope finally solve the mystery of why galaxies stop making stars?
Black hole jets or a hot gas shield: what is the ultimate killer of massive galaxies?
Crossing the 10^12.5 Solar Mass Barrier: The Critical Threshold That Halts Galaxy Growth
Overview
Recent research, using advanced simulations and JWST observations, has revealed a universal critical mass threshold—log(M_halo) ~ 12.5—at which galaxies dramatically reduce their star formation efficiency and largely stop growing. When a galaxy’s dark matter halo exceeds this mass, its ability to form new stars declines sharply, leading to a decrease in the stellar mass-halo mass ratio and a saturation in metallicity. This marks a transition from active, star-forming galaxies to mature, quiescent ones. Identifying this threshold helps scientists better model and predict how galaxies evolve across the universe.