The Las Campanas Infrared Survey. III. The<i>H</i>‐Band Imaging Survey and the Near‐Infrared and Optical Photometric Catalogs
Bibliographic record
Abstract
The Las Campanas Infrared Survey, based on broadband optical and near-infrared photometry, is designed to robustly identify a statistically significant and representative sample of evolved galaxies at redshifts z > 1. We have completed an H -band imaging survey over 1.1 deg 2 of sky in six separate fields. The average 5 σ detection limit in a 4'' diameter aperture is H ~ 20.8. Here we describe the design of the survey, the observation strategies, data-reduction techniques, and object identification procedures. We present sample near-infrared and optical photometric catalogs for objects identified in two survey fields. The optical images of the Hubble Deep Field-South region obtained from the literature reach 5 σ detection thresholds in a 4'' diameter aperture of U ~ 24.6, B ~ 26.1, V ~ 25.6, R ~ 25.1, and I ~ 24.2 mag. The optical images of the Chandra Deep Field-South region obtained from our own observations reach 5 σ detection thresholds in a 4'' diameter aperture of V ~ 26.8, R ~ 26.2, I ~ 25.3, and z ' ~ 23.7 mag. We perform object detection in all bandpasses and identify ≳ 54,000 galaxies over 1408 arcmin 2 of sky in the two fields. Of these galaxies, ~14,000 are detected in the H band and ~2000 have the colors of evolved galaxies, I - H ≳ 3, at z ≳ 1. We find that (1) the differential number counts N ( m ) for the H -band-detected objects has a slope of d log N ( m )/ dm = 0.45 ± 0.01 mag -2 at H ≲ 19 and 0.27 ± 0.01 mag -2 at H ≳ 19, with a mean surface density ≈7200 deg -2 mag -1 at H = 19. In addition, we find that (2) the differential number counts for the H -band-detected red objects has a very steep slope, d log N ( m ; I - H ≳ 3)/ dm = 0.84 ± 0.06 mag -2 at H ≲ 20 and 0.32 ± 0.07 mag -2 at H ≳ 20, with a mean surface density ≈3000 deg -2 mag -1 at H = 20. Finally, we find that (3) galaxies with red optical to near-IR colors ( I - H > 3) constitute ≈20% of the H -band-detected galaxies at H ≲ 21, but only ≈2% at H ≲ 19. We show that red galaxies are strongly clustered, which results in a strong field-to-field variation in their surface density. Comparisons of observations and predictions based on various formation scenarios indicate that these red galaxies are consistent with mildly evolving early-type galaxies at z ~ 1, although with a significant amount of ongoing star formation, as indicated by the large scatter in their V - I colors.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.003 | 0.003 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.009 | 0.005 |
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".