An ultraviolet-selected galaxy redshift survey - III. Multicolour imaging and non-uniform star formation histories
Bibliographic record
Abstract
We present panoramic u′ and optical ground‐based imaging observations of a complete sample of low‐redshift (0 < z < 0.4) galaxies selected in the ultraviolet (UV) at 2000 Å using the balloon‐borne FOCA instrument of Milliard et al. This survey is highly sensitive to newly formed massive stars and hence to actively star‐forming galaxies. We use the new data to investigate further the optical, stellar population and star formation properties of this unique sample, deriving accurate galaxy types and k‐corrections based on the broad‐band spectral energy distributions. When combined with our earlier spectroscopic surveys, these new data allow us to compare star formation measures derived from aperture‐corrected Hα line fluxes, and UV(2000 Å) and u′(3600 Å) continuum fluxes on a galaxy‐by‐galaxy basis. As expected from our earlier studies, we find broad correlations over several decades in luminosity between the different dust‐corrected star formation diagnostics, though the scatter is larger than that from observational errors, with significant offsets from trends expected according to simple models of the star formation histories (SFHs) of galaxies. Popular galaxy spectral synthesis models with varying metallicities and/or initial mass functions seem unable to explain the observed discrepancies. We investigate the star formation properties further by modelling the observed spectroscopic and photometric properties of the galaxies in our survey. We find that nearly half of the galaxies surveyed possess features that appear incompatible with simple constant or smoothly declining SFHs, favouring instead irregular or temporally varying SFHs. We demonstrate how this can reconcile the majority of our observations, enabling us to determine empirical corrections that can be used to calculate intrinsic star formation rates (as derived from Hα luminosities) from measures based on UV (or u′) continuum observations alone. We discuss the broader implications of our finding that a significant fraction of star‐forming galaxies have complex SFHs, particularly in the context of recent determinations of the cosmic SFH.
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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 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".