The Las Campanas Infrared Survey. IV. The Photometric Redshift Survey and the Rest‐Frame<i>R</i>‐Band Galaxy Luminosity Function at 0.5 ≤ <i>z</i> ≤ 1.5
Bibliographic record
Abstract
We present rest-frame, R -band, galaxy luminosity function measurements for three different redshift ranges: 0.5 ≤ z ≤ 0.75, 0.75 ≤ z ≤ 1.0, and 1.0 ≤ z ≤ 1.5. Our measurements are based on photometric redshifts for ~3000 H -band-selected galaxies with apparent magnitudes 17 ≤ H ≤ 20 from the Las Campanas Infrared Survey. We show that our photometric redshifts are accurate with an rms dispersion between the photometric and spectroscopic redshifts of σ z /(1 + z ) ≈ 0.08. Using galaxies identified in the Hubble Deep Field-South and Chandra Deep Field-South regions, we find, respectively, that 7.3% ± 0.2% and 16.7% ± 0.4% of the H ≤ 20 galaxies are at z ≥ 1. We first demonstrate that the systematic uncertainty inherent in the luminosity function measurements because of uncertainties in photometric redshifts is nonnegligible and therefore must be accounted for. We then develop a technique to correct for this systematic error by incorporating the redshift error functions of individual galaxies in the luminosity function analysis. The redshift error functions account for the non-Gaussian characteristics of photometric redshift uncertainties. They are the products of a convolution between the corresponding redshift likelihood functions of individual galaxies and a Gaussian distribution function that characterizes template-mismatch variance. We demonstrate, based on a Monte Carlo simulation, that we are able to completely recover the bright end of the intrinsic galaxy luminosity function using this technique. Finally, we calculate the luminosity function separately for the total H -band-selected sample and for a subsample of early-type galaxies that have a best-fit spectral type of E/S0 or Sab from the photometric redshift analysis. The primary results of this analysis are (1) the galaxy luminosity functions are consistent with a Schechter form, (2) the evolution of the comoving luminosity density ℓ of H -band-selected galaxies is characterized by Δ log ℓ/Δ log(1 + z ) = 0.6 ± 0.1 at rest frame 6800 Å, and (3) ℓ R for color-selected, early-type galaxies exhibits moderate evolution from z ~ 1.5 to ~0.3. Specifically, ℓ R for these red galaxies brighter than 1.0 (1.6) L * could decrease with increasing redshift by at most a factor of 3 (6) over this redshift range after removing possible stellar brightening according to the most extreme stellar evolution scenario.
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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 | 0.003 | 0.003 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.005 | 0.002 |
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".