Study Identifies Multiple Pathways for Dwarf Galaxy Compaction in TNG50 Simulation
A new study using the TNG50 cosmological simulation identifies three distinct physical mechanisms by which dwarf galaxies become unusually compact when they fall into larger galaxy environments. The research analyzed dwarf galaxies with stellar masses between roughly 250 million and 1.6 billion solar masses at the present epoch, distinguishing compact systems from normal-sized ones based on the size-mass relation. The findings clarify how environment — through tidal stripping, gas accretion dynamics, and ram pressure — shapes the structural evolution of satellite galaxies.
Researchers using the TNG50 high-resolution hydrodynamical simulation have identified two robust and one tentative pathway through which dwarf satellite galaxies become compact. The first pathway applies to dark-matter-rich compact satellites in relatively sparse environments: fewer mergers favor the accretion of low-angular-momentum gas, driving concentrated central star formation and compaction — a mechanism previously documented in central (non-satellite) galaxies. The second pathway, affecting most dark-matter-poor satellites, involves tidal stripping of outer stars, with the process accelerating by at least 15 percent when residual gas is present. A third, more tentative channel is identified for a small subset of very metal-rich, dark-matter-poor compact satellites, where a starburst triggered by ram pressure compression near first pericentre initiates compaction, which is then continued by subsequent tidal stripping. The study also discusses how numerical effects in the simulation may influence these conclusions. The paper has been accepted for publication in Monthly Notices of the Royal Astronomical Society.
What's missing
The study relies entirely on one simulation (TNG50) and does not directly compare its compaction pathways against observational data from real compact dwarf satellites. The generalizability of these results to other cosmological simulations with different feedback prescriptions remains an open question.
What different sources said
- arXiv astro-phCenter
CROCODILE-DWARF: Assembly and Kinematics of Field Dwarf Galaxies with GADGET4-OSAKA
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