The kiloparsec-scale gas kinematics in two star-forming galaxies at z ∼ 1.47 seen with ALMA and VLT-SINFONI
Bibliographic record
Abstract
We present Atacama Large Millimeter/submillimeter Array (ALMA) CO(J = 2–1) observations of two main-sequence star-forming galaxies at z ∼ 1.47 taken from the High-Z Emission Line Survey (HiZELS). These two systems have been previously reported to be molecular gas-rich |$f_{\rm H_2} \equiv M_{\rm H_2}/(M_{\rm H_2} + M_\star) \sim 0.8$|. We carried out a follow-up study to resolve, at ∼kpc-scales, the CO emission. These new observations are combined with our earlier ALMA observations (sensitive to diffuse CO emission) and compared with our previous H α-based study at matched spatial resolution. One target is marginally resolved in CO(2–1), showing complex dynamics with respect to the ionized gas traced by H α. While the other source is spatially resolved, enabling a detailed exploration of its internal dynamical properties. In this system, both gaseous phases show similar spatial extension, rotation velocities, and velocity dispersions (Vrot ∼ σv ∼ 100 km s−1) suggesting a rotational velocity to velocity dispersion ratio consistent with unity. By comparing the ionized and molecular gas tracers through the use of a two-dimensional kinematic model, we estimate a median depletion time τdep = 2.3 ± 1.2 Gyr for the galaxy as a whole. This value is in agreement with the average τdep value observed in local star-forming galaxies at similar spatial scales. Using a thick-disc dynamical modelling, we derive a dynamical mass Mdyn = (1.59 ± 0.19) × 1011 M⊙ within ≈6 kpc. This suggests a dark matter fraction (fDM ≡ MDM/Mdyn of 0.59 ± 0.10), in agreement with the average fDM value derived from stacked rotation curve analysis of galaxies at similar redshift range.
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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 | 0.001 | 0.000 |
| 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) | 0.000 | 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 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".