Probing the Stellar Populations and Star Formation History of Early-type Galaxies at 0 < z < 1.1 in the Rest-frame Ultraviolet
Bibliographic record
Abstract
Abstract We measure the evolution of the rest-frame near-ultraviolet (NUV)−V colors for early-type galaxies in clusters at 0 < z < 1.1 using data from the Hyper Suprime-Cam Subaru Strategic Program, CFHT Large Area U-band Deep Survey, and local Sloan Digital Sky Survey clusters observed with Galaxy Evolution Explorer. Our results show that there is an excess in the ultraviolet spectrum in most quiescent galaxies (compared to the expectations from models fitting their optical/infrared colors and spectra) below z ∼ 0.6, beyond which the excess UV emission fades rapidly. This evolution of the UV color is only consistent with the presence of a highly evolved, hot horizontal branch subpopulation in these galaxies (among the majority of cool and optically bright stars), comprising on average 10% of the total stellar mass and forming at z > 3. The blue UV colors of early-type galaxies at low–intermediate redshifts are likely driven by this subpopulation being enriched in helium up to ∼44%. At z > 0.8 (when the extra UV component has not yet appeared) the data allow us to constrain the star formation histories of galaxies by fitting models to the evolution of their UV colors: we find that the epoch at which the stellar populations formed lies in the range 3 < z form < 10 (corresponding to 0.5–2.2 Gyr after the Big Bang) with a star formation e-folding timescale of τ = 0.35–0.7 Gyr, suggesting that these galaxies formed the majority of stars at very high redshift, with a brief yet intense burst of star formation activity. The star formation history and chemical evolution of early-type galaxies resemble those of globular clusters, albeit on much larger scales.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
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".