Tracing Red Giant Members of the Globular Cluster Palomar 5 with APOGEE and Gaia
Bibliographic record
Abstract
Abstract The globular cluster Palomar 5 (Pal 5) is in the process of being tidally shredded as it orbits the Milky Way. Its core is currently at a heliocentric distance of ∼21 kpc, near apogalacticon (∼18 kpc), and it reaches ∼5–7 kpc at perigalacticon. Pal 5’s leading and trailing arms stretch over 20° on the sky, making them sensitive probes of the Milky Way’s mass distribution. In this work, we search for red giant members of Pal 5 using spectroscopic data from APOGEE DR17 and photometric and astrometric data from Gaia data release 3. Based on position and proper motion, we identify eight members of Pal 5: six in the core and two in the stream. The clustering algorithm HDBSCAN finds these same eight. We then use chemical tagging with APOGEE abundances to search for additional members across five APOGEE fields overlapping Pal 5. While several dozen candidates are identified, most deviate (some significantly) from known kinematic and color–magnitude trends, suggesting that they are less likely to be true members. We estimate the expected number of giants in the APOGEE pointings based on the area and stellar mass of the streams. Given APOGEE’s limiting magnitude, we find that few, if any, new giants are expected, especially if the stream is more diffuse at these locations. Our results support the presence of density variations in Pal 5’s tidal streams, consistent with earlier studies attributing such features to baryonic perturbers in the Milky Way, dark matter subhalos, or interactions with passing globular clusters.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 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".