From giant clumps to clouds IV: extreme star-forming clumps on top of universal cloud scaling relations in gas-rich galaxies
Astronomy & Astrophysics(2024)
摘要
The clumpy nature of gas-rich galaxies at cosmic noon raises the question of
universality of the scaling relations and average properties of the
star-forming structures. Using controlled simulations of disk galaxies and
varying only the gas fraction, we show that the influence of the galactic
environments (large-scale turbulence, tides, shear) contributes, together with
the different regime of instabilities, to setting a diversity of physical
conditions for the formation and evolution of gas clumps from low to high gas
fractions. However, the distributions of gas clumps at all gas fractions follow
similar scaling relations as Larson's, suggesting the universality of median
properties. Yet, we find that the scatter around these relations significantly
increases with the gas fraction, allowing for the presence of massive, large,
and highly turbulent clouds in gas-rich disks in addition to a more classical
population of clouds. Clumps with an excess of mass for their size are slightly
denser, more centrally concentrated, and host more abundant and faster star
formation. We find that the star formation activity (rate, efficiency,
depletion time) correlates much more strongly with the excess of mass than with
the mass itself. Our results suggest the existence of universal scaling
relations for gas clumps but with redshift-dependent scatters, which calls for
deeper and more complete census of the populations of star-forming clumps and
young stellar clusters at cosmic noon and beyond.
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