A population of faint, old, and massive quiescent galaxies at 3 < z < 4 revealed by JWST NIRSpec Spectroscopy
Bibliographic record
Abstract
Abstract The confirmation of the presence of very massive quiescent galaxies at epochs only 1–2 Gyr after the Big Bang [1–8] has challenged models of cosmology and galaxy formation [9]. Producing sufficient numbers of these requires abundant numbers of the host dark matter halos to have been assembled and sufficient time for star formation to proceed extremely quickly and then cease just as rapidly. Ground-based spectroscopy has suggested ages of 200–300 Myr[3] at redshifts 3 < z < 4. The true number and ages of these objects have however been highly uncertain as ground-based spectra has been limited to the bright- est of them [e.g. 3, 5], at wavelengths ∼ 2μm, which introduces a signficant potential bias towards younger objects [7]. The launch of the James Webb Space Telescope (JWST) enables dramatically more sensitive and constraining spectroscopic observations due to the very low sky background, sharp image quality, and access to wavelengths beyond 2μm. Here we report JWST NIR- Spec [10] (0.6–5.3μm) observations of five new quiescent galaxy candidates that were beyond the limit of previous ground-based spectroscopy. The high signal:noise spectra of galaxies with continuum significantly fainter than ear- lier confirmations show that they are also at redshifts 3 < z < 4, and that they have substantial stellar masses of ∼ 0.5−1.2×1011 M⊙ comparable to massive galaxies in the nearby Universe. One of the galaxies has been quenched for ∼> 1 billion years pointing to a presence of substantially older and fainter galaxies than those revealed so far by ground-based spectroscopy. This suggests that some of the massive galaxies have very early formation epochs (during the epoch of reionization, z ∼> 6) pointing to a need for high conversion rates of baryons to stars in the first massive galaxy halos in the early Universe [11, 12].
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".