A Thorough View of the Nuclear Region of NGC 253: Combined Herschel, SOFIA, and APEX Data Set
Bibliographic record
Abstract
Abstract We present a large set of spectral lines detected in the 40″ central region of the starburst galaxy NGC 253. Observations were obtained with the three instruments SPIRE, PACS, and HIFI on board the Herschel Space Observatory, upGREAT on board the SOFIA airborne observatory, and the ground-based Atacama Pathfinder EXperiment telescope. Combining the spectral and photometry products of SPIRE and PACS, we model the dust continuum spectral energy distribution (SED) and the most complete 12CO line SED reported so far toward the nuclear region of NGC 253. The properties and excitation of the molecular gas were derived from a three-component non-LTE radiative transfer model, using the SPIRE 13CO lines and ground-based observations of the lower-J 13CO and HCN lines, to constrain the model parameters. Three dust temperatures were identified from the continuum emission, and three components are needed to fit the full CO line SED. Only the third CO component (fitting mostly the HCN and PACS 12CO lines) is consistent with a shock-/mechanical-heating scenario. A hot core chemistry is also argued as a plausible scenario to explain the high-J 12CO lines detected with PACS. The effect of enhanced cosmic-ray ionization rates, however, cannot be ruled out and is expected to play a significant role in the diffuse and dense gas chemistry. This is supported by the detection of ionic species like OH+ and H2O+, as well as the enhanced fluxes of the OH lines with respect to those of H2O lines detected in both PACS and SPIRE spectra.
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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) | 0.001 | 0.001 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".