The DEEP Groth Strip Survey. VII. The Metallicity of Field Galaxies at 0.26 <<i>z</i>< 0.82 and the Evolution of the Luminosity‐Metallicity Relation
Bibliographic record
Abstract
Using spectroscopic data from the Deep Extragalactic Evolutionary Probe Groth Strip Survey (DGSS), we analyze the gas-phase oxygen abundances in the warm ionized medium for 64 emission-line field galaxies in the redshift range 0.26 < z < 0.82. These galaxies comprise a small subset selected from among 693 objects in the DGSS. They are chosen for chemical analysis by virtue of having the strongest emission lines. Oxygen abundances relative to hydrogen are in the range 8.4 < 12 + log(O/H) < 9.0 with typical internal plus systematic measurement uncertainties of 0.17 dex. The 64 DGSS galaxies collectively exhibit an increase in metallicity with B -band luminosity, i.e., an L - Z relation like that seen among local galaxies. Using the DGSS sample and local galaxy samples for comparison, we searched for a "second parameter" that might explain some of the dispersion seen in the L - Z relation. Parameters such as galaxy color, emission-line equivalent width, and effective radius were explored but found to be uncorrelated with residuals from the mean L - Z relation. Subsets of DGSS galaxies binned by redshift also exhibit L - Z correlations with slopes and zero points that evolve smoothly with redshift. DGSS galaxies in the highest redshift bin ( z = 0.6-0.82) are brighter, on average, by ~1 mag at fixed metallicity than those in the lowest DGSS redshift bin ( z = 0.26-0.40) and by up to ~2.4 mag compared to local ( z < 0.1) emission-line field galaxies. Alternatively, DGSS galaxies in the highest redshift bin ( z = 0.6-0.82) are, on average, 40% (0.15 dex) more metal-poor at fixed luminosity than local ( z < 0.1) emission-line field galaxies. For 0.6 < z < 0.8 galaxies, the offset from the local L - Z relation is greatest for objects at the low-luminosity ( M B > -19) end of the sample and is vanishingly small for objects at the high-luminosity end of the sample ( M B ~ -22). We compare these data to simple single-zone, exponential-infall PÉGASE2 models, which follow the chemical and luminous evolution of galaxies from formation to z = 0. A narrow range of model parameters can qualitatively produce the slope of the L - Z relation and the observed evolution of slope and zero point with redshift when at least two of the following are true: (1) low-mass galaxies have lower effective chemical yields than massive galaxies, (2) low-mass galaxies assemble on longer timescales than massive galaxies, and (3) low-mass galaxies begin the assembly process at a later epoch than massive galaxies. The single-zone models do a reasonable job of reproducing the observed evolution for the low-luminosity galaxies ( M B ~ -19) in our sample but fail to predict the relative lack of evolution in the L - Z plane observed for the most luminous galaxies ( M B ~ -22). More realistic multizone models will be required to explain the chemoluminous evolution of large galaxies.
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 | 0.002 |
| 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) | 0.005 | 0.003 |
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".