The Molecular Outflow in NGC 253 at a Resolution of Two Parsecs
Bibliographic record
Abstract
Abstract We present 0.″15 (∼2.5 pc) resolution ALMA CO(3–2) observations of the starbursting center in NGC 253. Together with archival ALMA CO(1–0) and CO(2–1) data, we decompose the emission into disk and nondisk components. We find ∼7%–16% of the CO luminosity to be associated with the nondisk component (1.2–4.2 × 10 7 K km s −1 pc 2 ). The total molecular gas mass in the center of NGC 253 is ∼3.6 × 10 8 M ⊙ with ∼0.5 × 10 8 M ⊙ (∼15%) in the nondisk component. These measurements are consistent across independent mass estimates through three CO transitions. The high-resolution CO(3–2) observations allow us to identify the molecular outflow within the nondisk gas. Using a starburst conversion factor, we estimate the deprojected molecular mass outflow rate, kinetic energy, and momentum in the starburst of NGC 253. The deprojected molecular mass outflow rate is in the range of ∼14–39 M ⊙ yr −1 with an uncertainty of 0.4 dex. The large spread arises due to different interpretations of the kinematics of the observed gas while the errors are due to unknown geometry. The majority of this outflow rate is contributed by distinct outflows perpendicular to the disk, with a significant contribution by diffuse molecular gas. This results in a mass-loading factor in the range η ∼ 8−20 for gas ejected out to ∼300 pc. We find the kinetic energy of the outflow to be ∼2.5–4.5 × 10 54 erg and a typical error of ∼0.8 dex, which is ∼0.1% of the total or ∼8% of the kinetic energy supplied by the starburst. The outflow momentum is 4.8–8.7 × 10 8 M ⊙ km s −1 (∼0.5 dex error) or ∼2.5%–4% of the kinetic momentum released into the ISM by the feedback. The unknown outflow geometry and launching sites are the primary sources of uncertainty in this study.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| 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".