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A massive, dead disk galaxy in the early Universe.
Sune Toft1, Johannes Zabl1,2, Johan Richard3
1Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 32, København Ø, 2100, Denmark.
Nature
|June 23, 2017
Summary
Massive galaxies at redshift z=2 were surprisingly found to be fast-spinning disks, not compact starbursts. This challenges the merger-driven model for early galaxy evolution and suggests disk formation pathways.
Area of Science:
- Cosmic evolution
- Galaxy formation and evolution
- Observational astrophysics
Background:
- Massive galaxies at redshift z=2 were often compact and had ceased star formation.
- The prevailing theory suggested these galaxies formed via intense nuclear starbursts and grew through mergers.
- Validating this model requires high-resolution observations of galactic centers, which are observationally challenging.
Purpose of the Study:
- To investigate the formation pathways of compact, massive galaxies at high redshift.
- To test the prevailing model of merger-driven starbursts for early massive galaxy formation.
- To understand the structural and kinematic evolution of early galaxies.
Main Methods:
- Utilized gravitational lensing to achieve higher resolution of a distant galaxy's core.
- Analyzed stellar populations and kinematics of a lensed galaxy at redshift z=2.1478.
- Interpreted observational data to infer formation mechanisms.
Main Results:
- A lensed compact galaxy at z=2.1478 was identified as a fast-spinning, rotationally supported disk galaxy.
- The galaxy's stars formed within a disk, contradicting the nuclear starburst hypothesis.
- Evidence suggests cold gas streams fed the galaxy until shock heating by the dark matter halo.
Conclusions:
- Early massive galaxies that ceased star formation likely underwent significant structural and kinematic transformations.
- Disk formation, not solely merger-driven starbursts, played a crucial role in the evolution of early massive galaxies.
- This finding necessitates revising models of galaxy evolution to include disk-based formation and evolution pathways.
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