An ISOCAM survey through gravitationally lensing galaxy clusters
Bibliographic record
Abstract
Observations of the core of the massive cluster Cl 0024+1654, at a redshift , were obtained with the Infrared Space Observatory using ISOCAM at 6.7 μm (hereafter 7 μm) and 14.3 μm (hereafter 15 μm). Thirty five sources were detected at 15 μm and thirteen of them are spectroscopically identified with cluster galaxies. The remaining sources consist of four stars, one quasar, one foreground galaxy, three background galaxies and thirteen sources with unknown redshift. The sources with unknown redshift are all likely to be background sources that are gravitationally lensed by the cluster. The spectral energy distributions (SEDs) of twelve cluster galaxies were fit from a selection of 20 models using the program GRASIL. The ISOCAM sources have best-fit SEDs typical of spiral or starburst models observed 1 Gyr after the main starburst event. The star formation rates were obtained for cluster members. The median infrared luminosity of the twelve cluster galaxies is ~ , with 10 having infrared luminosity above , and so lying near or above the threshold for identification as a luminous infrared galaxy (LIRG). The [] star formation rates obtained for 3 cluster galaxies are one to two orders of magnitude lower than the infrared values, implying that most of the star formation is missed in the optical because it is enshrouded by dust in the starburst galaxy. The cluster galaxies in general are spatially more concentrated than those detected at 15 μm. However the velocity distributions of the two categories are comparable. The colour-magnitude diagramme is given for the galaxies within the ISOCAM map. Only 20% of the galaxies that are significantly bluer than the cluster main sequence were detected at 15 μm, to the limiting sensitivity recorded. The counterparts of about half of the 15 μm cluster sources are blue, luminous, star-forming systems and the type of galaxy that is usually associated with the Butcher-Oemler effect. HST images of these galaxies reveal a disturbed morphology with a tendency for an absence of nearby companions. Surprisingly the counterparts of the remaining 15 μm cluster galaxies lie on the main sequence of the colour–magnitude diagramme. However in HST images they all have nearby companions and appear to be involved in interactions and mergers. Dust obscuration may be a major cause of the 15 μm sources appearing on the cluster main sequence. The majority of the ISOCAM sources in the Butcher-Oemler region of the colour–magnitude diagram are best fit by spiral-type SEDs whereas post-starburst models are preferred on the main sequence, with the starburst event probably triggered by interaction with one or more galaxies. Finally, the mid-infrared results on Cl 0024+1654 are compared with four other clusters observed with ISOCAM. Scaling the LIRG count in Cl 0024+1654 to the clusters Abell 370, Abell 1689, Abell 2218 and Abell 2390 with reference to their virial radii, masses, distances, and the sky area scanned in each case, we compared the number of LIRGs observed in each cluster. The number in Abell 370 is smaller than expected by about an order of magnitude, even though the two clusters are very similar in mass, redshift and optical richness. The number of LIRGs detected in each of Abell 1689, Abell 2218 and Abell 2390 is 0, whereas 3 were expected from the comparison with Cl 0024+1654. A comparison of the mid-infrared sources in Abell 1689 and Abell 2218 shows that the sources in Abell 1689 are more luminous and follow the same trend identified in the comparison between Cl 0024+1654 and Abell 370. These trends seem to be related to the dynamical status and history of the clusters.
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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 | 0.004 | 0.003 |
| 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) | 0.003 | 0.001 |
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".