What the study found
The study found that massive quiescent galaxies, meaning galaxies with little or no current star formation, are surprisingly common between redshift 2 and 5. The authors report number densities of at least about 10^-5 Mpc^-3 by 4 < z < 5.
Why the authors say this matters
The authors say these are the most complete spectroscopic estimates available before cosmic noon, a common term for the era when the universe's star formation activity was especially high. They also conclude that the results challenge most galaxy evolution simulations, which at z > 3 fail to make enough massive quiescent galaxies.
What the researchers tested
The researchers used JWST NIRSpec PRISM spectra from RUBIES, together with NIRCam photometry, to estimate the number density of massive galaxies with stellar mass above log(M*/M⊙) > 10.3. They identified quiescent candidates using principal component analysis and spectrophotometric fitting, then corrected for survey incompleteness by inverting the RUBIES selection function.
What worked and what didn't
The RUBIES spectra and targeting strategy allowed the authors to infer physical properties and number densities with high confidence, according to the abstract. Their inferred number densities are consistent with earlier JWST photometry-based studies and smaller-area surveys, but six state-of-the-art cosmological simulations generally underproduce these galaxies at z > 3.
What to keep in mind
The summary provided does not describe detailed limitations beyond the need to correct for survey incompleteness. The findings apply to massive quiescent galaxies at 2 < z < 5 and are based on the RUBIES sample and the methods described in the abstract.
Key points
- The study estimates number densities for massive quiescent galaxies at 2 < z < 5.
- By 4 < z < 5, the number density is reported as ≳10^-5 Mpc^-3.
- The authors used JWST NIRSpec PRISM spectra from RUBIES plus NIRCam photometry.
- Quiescent candidates were selected with principal component analysis and spectrophotometric fitting.
- Most compared cosmological simulations fail to produce enough massive quiescent galaxies at z > 3.
Disclosure
- Research title:
- Massive quiescent galaxies are common from redshift 2 to 5
- Authors:
- Yunchong Zhang, Anna de Graaff, David J. Setton, Sedona H. Price, Rachel Bezanson, Claudia del P. Lagos, Sam E. Cutler, Ian McConachie, Nikko J. Cleri, Olivia R. Cooper, Rashmi Gottumukkala, Jenny E. Greene, Michaela Hirschmann, Gourav Khullar, Ivo Labbé, Joel Leja, Michael V. Maseda, Jorryt Matthee, Tim B. Miller, Themiya Nanayakkara, Katherine A. Suess, Bingjie Wang, Katherine E. Whitaker, Christina C. Williams
- Publication date:
- 2026-01-27
- OpenAlex record:
- View
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