A Survey for Infall Motions toward Starless Cores. III. CS (3–2) and DCO <sup>+</sup> (2–1) Observations
Bibliographic record
Abstract
We present CS (3-2) and DCO + (2-1) observations of 94 starless cores and compare the results with previous CS (2-1) and N 2 H + (1-0) observations to study inward motions in starless cores. Eighty-four cores were detected in both CS and DCO + lines. A significant number of CS (3-2) profiles and a small number of DCO + (2-1) lines show the classical "infall asymmetry" similar to that seen in CS (2-1) observations. The DCO + (2-1) lines, however, usually show a single Gaussian peak. The integrated intensity of N 2 H + correlates well with that of DCO + (2-1) but poorly with that of CS (2-1) and CS (3-2), suggesting that CS suffers significantly more depletion onto grains than do either DCO + or N 2 H + . Despite these depletion effects, there is evidently enough optical depth for the CS (3-2) and CS (2-1) spectral lines to exhibit infall asymmetries. The velocity shifts of the CS (3-2) and (2-1) lines with respect to N 2 H + correlate well with each other and have similar distributions. This implies that, in many cores, systematic inward motions of gaseous material may occur over a range of density of at least a factor ∼4. We identify 18 infall candidates based on observations of CS (3-2), CS (2-1), DCO + (2-1) and N 2 H + (1-0). The eight best candidates, L1355, L1498, L1521F, L1544, L158, L492, L694-2, and L1155C-1, each show at least four indications of infall asymmetry and no counterindications. Fits of the spectra to a two-layer radiative transfer model in ten infall candidates suggest that the median effective line of sight speed of the inward-moving gas is ∼0.07 km s -1 for CS (3-2) and ∼0.04 km s -1 for CS (2-1). Considering that the optical depth obtained from the fits is usually smaller in CS (3-2) than in (2-1) line, this may imply that CS (3-2) usually traces inner denser gas in higher inward motions than CS (2-1). However, it is also possible that this conclusion is not representative of all starless core infall candidates, because of the statistically small number analyzed here. Further line observations will be useful to test this conclusion.
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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 | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 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".