Synthetic observations of spiral arm tracers of a simulated Milky Way analog
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Bibliographic record
Abstract
Context. The Faraday rotation measure (RM) is often used to study the magnetic field strength and orientation within the ionized medium of the Milky Way. Recent observations indicate an RM magnitude in the spiral arms that exceeds the commonly assumed range. This raises the question of how and under what conditions spiral arms create such strong Faraday rotation.<br/>Aims. We investigate the effect of spiral arms on Galactic Faraday rotation through shock compression of the interstellar medium. It has recently been suggested that the Sagittarius spiral arm creates a strong peak in Faraday rotation where the line of sight is tangent to the arm, and that enhanced Faraday rotation follows along side lines which intersect the arm. Here, we seek to understand the physical conditions that may give rise to this effect and the role of viewing geometry.<br/>Methods. We apply a magnetohydrodynamic simulation of the multi-phase interstellar medium in a Milky Way type spiral galaxy disk in combination with radiative transfer in order to evaluate different tracers of spiral arm structures. For observers embedded in the disk, dust intensity, synchrotron emission and the kinematics of molecular gas observations are derived to identify which spiral arm tangents are observable. Faraday rotation measures are calculated through the disk and evaluated in the context of different observer positions. The observer’s perspectives are related to the parameters of the local bubble surrounding the observer and their contribution to the total Faraday rotation measure along the line of sight.<br/>Results. We reproduce a scattering of tangent points for the different tracers of about 6° per spiral arm similar to the Milky Way. As for the RM, the model shows that compression of the interstellar medium and associated amplification of the magnetic field in spiral arms enhances Faraday rotation by a few hundred rad m¯<sup>2</sup> on top of the mean contribution of the disk. The arm-inter-arm contrast in Faraday rotation per unit distance along the line of sight is approximately ∼ 10 in the inner Galaxy, fading to ∼ 2 in the outer Galaxy in tandem with the waning contrast of other tracers of spiral arms. We identify a shark-fin like pattern in the RM Milky Way observations as well as the synthetic data that is characteristic for a galaxy with spiral arms.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| 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 | 0.000 | 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 it