Stable but Wrong: An Inference Limit in Galactic Archaeology
TLDR
Galactic archaeology inferences can be "stable but wrong," showing systematic age offsets despite small uncertainties due to observational quality.
Key contributions
- Challenges the assumption that increased data quality always leads to accurate physical inferences.
- Demonstrates observational quality can introduce systematic bias in stellar age inference for Milky Way history.
- Identifies a "stable-but-wrong" state where inferred formation timescales are systematically off by 0.5-1 Gyr.
- This bias persists despite small statistical uncertainties, validated against an asteroseismic reference.
Why it matters
This paper reveals a critical limitation in statistical inference for galactic archaeology, showing that observational quality can lead to systematically biased results. It urges a re-evaluation of past conclusions about the Milky Way's formation history and emphasizes careful consideration of data quality in future studies.
Original Abstract
Statistical inference in observational science typically relies on a fundamental assumption: as sample size increases and uncertainties decrease, the inferred results should converge to the true physical quantities. This assumption underpins the notion that big data lead to more reliable conclusions. In Galactic archaeology, stellar ages inferred from spectroscopic surveys are widely used to reconstruct the formation history of the Milky Way disk. The age metallicity relation (AMR) and its derived formation timescale are often regarded as key physical diagnostics of early disk evolution. This interpretation carries an implicit premise: that observational quality does not introduce systematic bias into age inference. Here we show that this premise may fail. Using a large sample of subgiant stars, we identify a region in the observational quality parameter space (signal-to-noise ratio and parallax precision) where the inferred formation timescale exhibits a systematic offset of 0.5-1 Gyr relative to an independent asteroseismic reference, while the statistical uncertainties remain small, thus producing a stable-but-wrong inference state.
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