The COSMOS-Wall at <i>z</i> ∼ 0.73: Star-forming galaxies and their evolution in different environments
Bibliographic record
Abstract
Aims. We present a study of the evolution of star-forming galaxies within what is known as the Wall structure at z ∼ 0.73 in the field of the COSMOS survey. We use a sample of star-forming galaxies from a comprehensive range of environments and across a wide stellar mass range. We discuss the correlation between the environment and the galaxy’s internal properties, including its metallicity from the present-day gas-phase value and its past evolution as imprinted in its stellar populations. Methods. We measured emission-line fluxes from the stacked spectra of galaxies selected within small stellar mass bins and in different environments. These fluxes were then converted to gas-phase metallicities. In addition, we built a simple yet comprehensive galaxy chemical evolution model, which is constrained by the gas-phase metallicities, stacked spectra, and photometry of galaxies to reach a full description of the galaxies’ past star formation and chemical evolution histories in different environments. Parameters derived from best-fit models provide insights into the physical process behind the evolution. Results. We reproduce the downsizing formation of galaxies in their star formation histories and in their chemical evolution histories at z ∼ 0.73 so that more massive galaxies tend to grow their stellar mass and become enriched in metals earlier than less massive ones. In addition, the current gas-phase metallicity of a galaxy and its past evolution correlate with the environment it inhabits. Galaxies in groups, especially massive groups that have X-ray counterparts, tend to have higher gas-phase metallicities and are enriched in metals earlier than field galaxies of similar stellar mass. Galaxies in the highest stellar mass bin and located in X-ray groups exhibit a more complex and varied chemical composition. Conclusions. The evolution of a galaxy, including its star formation history and chemical enrichment history, exhibits a notable dependence on the environment where the galaxy is located. This dependence is revealed in our sample of star-forming galaxies in the Wall region at a redshift of z ∼ 0.73. Strangulation due to interactions with the group environment, leading to an early cessation of gas supply, may have driven the faster mass growth and chemical enrichment observed in group galaxies. Additionally, the removal of metal-enriched gas could play a key role in the evolution of the most massive galaxies. Alternative mechanisms other than environmental processes are also discussed.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".