Accelerating Redshift-Conditioned Galaxy Image Synthesis with One-step Generative Modeling

TL;DR

This paper explores efficient redshift-conditioned galaxy image synthesis using diffusion models and pixel-MeanFlow, demonstrating that one-step generative models can produce realistic galaxy morphologies with significantly reduced computational costs.

Contribution

It introduces and evaluates one-step generative modeling techniques for galaxy images, achieving a balance between accuracy and efficiency in astrophysical image synthesis.

Findings

Pixel-MeanFlow enables single-step galaxy image generation with competitive morphology statistics.

Second-order samplers improve efficiency over traditional DDIM sampling.

One-step models recover key galaxy morphology statistics at much lower computational cost.

Abstract

Understanding galaxy morphology evolution across cosmic time requires models that can generate realistic galaxy populations conditioned on redshift. In this work, we study efficient redshift-conditioned generative modeling for astrophysical image synthesis using diffusion models and pixel-MeanFlow. We first review the connections between score-based diffusion models, Flow Matching, one-step generative models, and modern diffusion samplers. We then evaluate DDPM, DDIM, DEIS-AB2, DPM++2M, and one-step pixel-MeanFlow on the GalaxiesML-64 dataset using morphology-based metrics, including ellipticity, semi-major axis, S\'ersic index, and isophotal area. Our results show a clear accuracy-efficiency trade-off: standard DDPM sampling achieves the best distributional fidelity but requires high computational cost, while second-order samplers substantially improve efficiency over DDIM. Pixel-MeanFlow enables single-step generation and achieves competitive performance on several morphology statistics, though it remains weaker than many-step DDPM for fine-grained structure. Our results demonstrate that one-step generative models can recover key galaxy morphology statistics at orders-of-magnitude lower computational cost, opening a path toward efficient conditional simulators for large cosmological surveys and simulation-based scientific inference.