Central molecular zones in galaxies:<sup>12</sup>CO-to-<sup>13</sup>CO ratios, carbon budget, and<i>X</i>factors
Bibliographic record
Abstract
We present ground-based measurements of 126 nearby galaxy centers in12CO and 92 in13CO in various low-Jtransitions. More than 60 galaxies were measured in at least four lines. The average relative intensities of the first fourJ12CO transitions are 1.00:0.92:0.70:0.57. In the first threeJtransitions, the average12CO-to-13CO intensity ratios are 13.0, 11.6, and 12.8, with individual values in any transition ranging from 5 to 25. The sizes of central CO concentrations are well defined in maps, but poorly determined by multi-aperture photometry. On average, theJ = 1−012CO fluxes increase linearly with the size of the observing beam. CO emission covers only a quarter of the HI galaxy disks. Using radiative transfer models (RADEX), we derived model gas parameters. The assumed carbon elemental abundances and carbon gas depletion onto dust are the main causes of uncertainty. The new CO data and published [CI] and [CII] data imply that CO, C°, and C+each represent about one-third of the gas-phase carbon in the molecular interstellar medium. The mean beam-averaged molecular hydrogen column density isN(H2) = (1.5 ± 0.2)×1021cm−2. Galaxy center CO-to-H2conversion factors are typically ten times lower than the “standard” Milky WayX°disk value, with a meanX(CO) = (1.9 ± 0.2)×1019cm−2/K km s−1and a dispersion 1.7. The corresponding [CI]-H2factor is five times higher thanX(CO), withX[CI] = (9 ± 2)×1019cm−2/K km s−1. No unique conversion factor can be determined for [CII]. The low molecular gas content of galaxy centers relative to their CO intensities is explained in roughly equal parts by high central gas-phase carbon abundances, elevated gas temperatures, and large gas velocity dispersions relative to the corresponding values in galaxy disks.
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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 | 0.001 | 0.001 |
| 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".