RESOLVING THE FAR-IR LINE DEFICIT: PHOTOELECTRIC HEATING AND FAR-IR LINE COOLING IN NGC 1097 AND NGC 4559
Bibliographic record
Abstract
The physical state of interstellar gas and dust is dependent on the processes which heat and cool this medium. To probe heating and cooling of the interstellar medium over a large range of infrared surface brightness, on sub-kiloparsec scales, we employ line maps of [C ii ] 158 μm, [O i ] 63 μm, and [N ii ] 122 μm in NGC 1097 and NGC 4559, obtained with the Photodetector Array Camera & Spectrometer on board Herschel . We matched new observations to existing Spitzer Infrared Spectrograph data that trace the total emission of polycyclic aromatic hydrocarbons (PAHs). We confirm at small scales in these galaxies that the canonical measure of photoelectric heating efficiency, ([C ii ] + [O i ])/TIR, decreases as the far-infrared (far-IR) color, ν f ν (70 μm) ν f ν (100 μm), increases. In contrast, the ratio of far-IR cooling to total PAH emission, ([C ii ] + [O i ])/PAH, is a near constant ∼6% over a wide range of far-IR color, 0.5 < ν f ν (70 μm) ν f ν (100 μm) ≲ 0.95. In the warmest regions, where ν f ν (70 μm) ν f ν (100 μm) ≳ 0.95, the ratio ([C ii ] + [O i ])/PAH drops rapidly to 4%. We derived representative values of the local ultraviolet radiation density, G 0 , and the gas density, n H , by comparing our observations to models of photodissociation regions. The ratio G 0 / n H , derived from fine-structure lines, is found to correlate with the mean dust-weighted starlight intensity, 〈 U 〉, derived from models of the IR spectral energy distribution. Emission from regions that exhibit a line deficit is characterized by an intense radiation field, indicating that small grains are susceptible to ionization effects. We note that there is a shift in the 7.7/11.3 μm PAH ratio in regions that exhibit a deficit in ([C ii ] + [O i ])/PAH, suggesting that small grains are ionized in these environments.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".