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A massive, quiescent galaxy at a redshift of 3.717
Karl Glazebrook1, Corentin Schreiber2, Ivo Labbé2
1Centre for Astrophysics and Supercomputing, Swinburne University of Technology, PO Box 218, Hawthorn, Victoria 3122, Australia.
Nature
|April 7, 2017
Summary
Massive galaxies that ceased star formation were found in the early Universe. Spectroscopic confirmation of a galaxy at redshift 3.717 challenges current galaxy formation models.
Area of Science:
- Cosmology and Extragalactic Astronomy
- Galaxy Formation and Evolution
Background:
- Massive quiescent galaxies in the early Universe are observationally challenging to detect due to negligible ultraviolet emission.
- Previous deep near-infrared surveys identified such galaxies at redshift z≈2, with models explaining their rapid formation at z≈3-4.
- Deeper surveys suggested populations of massive, quiescent galaxies at even higher redshifts, but these were not predicted by theoretical models.
Purpose of the Study:
- To spectroscopically confirm the existence of massive, quiescent galaxies at very high redshifts (z > 3).
- To investigate the formation timescales and processes of these early massive galaxies.
- To test and potentially revise current theoretical models of early galaxy assembly.
Main Methods:
- Utilized extremely deep near-infrared surveys for initial identification of candidate galaxies.
- Performed spectroscopic observations to confirm redshift and stellar mass.
- Analyzed absorption line spectra to assess current star formation activity and derive galaxy age.
Main Results:
- Spectroscopically confirmed a massive quiescent galaxy at redshift z = 3.717 with a stellar mass of 1.7 × 10^11 solar masses.
- Determined the galaxy's age to be nearly half the age of the Universe at that epoch, with no signs of current star formation.
- Inferred that the majority of stars formed rapidly within the first billion years of cosmic history via an extreme starburst.
Conclusions:
- The existence of this massive, quiescent galaxy at z=3.717 demonstrates that significant galaxy assembly occurred much earlier than predicted by current models.
- The rapid, early starburst phase required to form such a galaxy challenges our understanding of early galaxy formation processes.
- These findings necessitate a substantial revision of theoretical frameworks describing the assembly of massive galaxies in the early Universe.
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