Ejection of High‐Velocity Stars from the Galactic Center by an Inspiraling Intermediate‐Mass Black Hole
Bibliographic record
Abstract
The presence of young stars near Sgr A* remains unexplained. One idea for their origin posits that the stars were brought in by an intermediate-mass black hole (IMBH) that inspiraled into the Galactic center a few million years ago. Yu & Tremaine have argued that in this case some old stars in the Sgr A* cusp would be ejected by hard gravitational collisions with the IMBH. We derive a general expression for the phase-space distribution of the ejected high-velocity stars, given the distribution function of the stars in the cusp. We compute it explicitly for the Peebles-Young distribution function of the cusp and model the time-dependent ejection of stars during the IMBH inspiral. We find that (1) the stars are ejected in a burst lasting a few dynamical friction timescales; if Gaia detects the ejected stars, they are likely to be produced by a single inspiral event. (2) If the inspiral is circular, then in the beginning of the burst the velocity vectors of the ejected stars cluster around the inspiral plane but rapidly isotropize as the burst proceeds. (3) If the inspiral is eccentric, then the stars are ejected in a broad jet roughly perpendicular to the IMBH orbit's Runge-Lenz vector. In a typical cusp the orbit will precess with a period of ~10 5 yr, and the rate of ejection into our part of the Galaxy (as defined by Gaia visibility) will be modulated periodically. Gaia , together with ground-based follow-up observations, will be able to clock many high-velocity stars back to their ejection, thus measuring some of the above phenomena. This would provide a clear signature of the IMBH inspiral in the past 10-20 Myr.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| 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".