Two radio supernova remnants discovered in the outer Galaxy
Bibliographic record
Abstract
Context.New and existing large-scale radio surveys of the Milky Way at centimetre wavelengths can play an important role in uncovering the hundreds of expected but missing supernova remnants in the Galaxy's interstellar medium.We report on the discovery of two supernova remnants (SNRs) designated G152.4-2.1 and G190.9-2.2, using Canadian Galactic Plane Survey data.Aims.The aims of this paper are, first, to present evidence that favours the classification of both sources as SNRs, and, second, to describe basic parameters (integrated flux density, spectrum, and polarization) as well as properties (morphology, line-of-sight velocity, distance and physical size) to facilitate and motivate future observations.Methods.Spectral and polarization parameters are derived from multiwavelength data from existing radio surveys carried out at wavelengths between 6 and 92 cm.In particular for the source G152.4-2.1 we also use new observations at 11 cm done with the Effelsberg 100 m telescope.The interstellar medium around the discovered sources is analyzed using 1-arcmin line data from neutral hydrogen (H i) and 45-arcsec 12 CO(J = 1 → 0).Results.G152.4-2.1 is a barrel shaped SNR with two opposed radio-bright polarized flanks on the north and south.The remnant, which is elongated along the Galactic plane is evolving in a more-or-less uniform medium.G190.9-2.2 is also a shell-type remnant with east and west halves elongated perpendicular to the plane, and is evolving within a low-density region bounded by dense neutral hydrogen in the north and south, and molecular ( 12 CO) clouds in the east and west.The integrated radio continuum spectral indices are -0.65 ± 0.05 and -0.66 ± 0.05 for G152.4-2.1 and G190.9-2.2 respectively.Both SNRs are approximately 1 kpc distant, with G152.4-2.1 being larger (32 × 30 pc in diameter) than G190.9-2.2 (18 × 16 pc).These two remnants are the lowest surface brightness SNRs yet catalogued at Σ 1 GHz < ∼ 5 × 10 -23 W m -2 Hz -1 sr -1 .
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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 | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".