Discovery of PAHs in the halo of NGC 5907
Bibliographic record
Abstract
We have used sensitive archival data from the Infrared Space Observatory (ISO) to make maps of the edge-on low SFR galaxy, NGC 5907, in 6 different MIR bands: LW2, LW5, LW6, LW7, LW8, and LW10, covering the spectrum from 6.5 to 15.0 μm and including several narrow bands that isolate the infrared aromatic spectral features commonly referred to as PAHs. Most of the MIR emission is dominated by PAHs and it is likely that emission from VSGs contribute only negligibly except in the broad IRAS-equivalent band. The flux ratios are typical of galaxies with low SFRs or quiesent regions within galaxies (e.g. M 83) and a very high PAH/continuum ratio is observed. The PAH emission follows the CO distribution and also shows some correlation within the disk with the λ850 μm distribution. However, the PAH emission also reaches larger galactocentric radii than the CO and other correlations suggest that the PAHs are also more widespread. A significant new discovery is the presence of PAHs in the halo of the galaxy. In the narrow bands that isolate single PAH features, the emission shows structure similar to high latitude features seen in other galaxies in other tracers. The features extend as far as 6.5 kpc from the plane but scale heights of 3.5 kpc are more typical. The λ11.3/λ7.7 ratio also appears to increase with distance from the major axis. To our knowledge, this is the first time PAHs have been seen in the halo of an external galaxy. Just as significantly, they are seen in a low SFR galaxy, suggesting that strong SNe and winds are not necessary for these large molecules to reach high latitudes.
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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 | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 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".