The Galaxy's Guide to the Tokenizer: A Benchmark for Scientific Foundation Models

Hugging Face Daily Papers Papers

Summary

This paper compares four tokenization methods (Affine, AIM, JetFormer, VQ-VAE) for astronomical images within a unified transformer framework, using 640,000 galaxy images to evaluate reconstruction quality, physical property prediction, and morphological preservation. It finds that no single method excels across all tasks, highlighting trade-offs in representation learning.

Tokenization is central to adapting scientific data for transformer-based foundation models, yet its impact on learned representations remains poorly understood. We compare four tokenization strategies, Affine, AIM, JetFormer, and VQ-VAE, within a unified transformer framework for astronomical imaging. Using 640,000 galaxy images from the DESI Legacy Survey and a shared AstroPT backbone, we evaluate each method on reconstruction fidelity and prediction of physical properties. Our results reveal trade-offs across approaches. The flow-based JetFormer achieves higher reconstruction quality, while VQ-VAE yields strong probe performance for galaxy physical properties. Affine and AIM better preserve localized morphological information. We find that reconstruction and representation quality are decoupled, and no single method consistently performs best across the tasks considered here. By grounding our evaluation in independently measured physical quantities, we hope this study serves to highlight the potential of scientific data as a basis for constructing interpretable benchmarks for foundation models.
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Source: https://huggingface.co/papers/2606.25610

Abstract

Four tokenization methods for astronomical images show distinct strengths in reconstruction quality, physical property prediction, and morphological preservation, with no single approach excelling across all tasks.

Tokenizationis central to adapting scientific data fortransformer-based foundation models, yet its impact on learned representations remains poorly understood. We compare fourtokenizationstrategies, Affine, AIM, JetFormer, andVQ-VAE, within a unified transformer framework forastronomical imaging. Using 640,000 galaxy images from theDESI Legacy Surveyand a sharedAstroPT backbone, we evaluate each method onreconstruction fidelityand prediction ofphysical properties. Our results reveal trade-offs across approaches. Theflow-basedJetFormer achieves higher reconstruction quality, whileVQ-VAEyields strong probe performance for galaxyphysical properties. Affine and AIM better preserve localizedmorphological information. We find that reconstruction and representation quality are decoupled, and no single method consistently performs best across the tasks considered here. By grounding our evaluation in independently measured physical quantities, we hope this study serves to highlight the potential of scientific data as a basis for constructing interpretable benchmarks for foundation models.

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