[论文解读] pop-cosmos: A comprehensive picture of the galaxy population from COSMOS data

Justin Alsing, Stephen Thorp+5 more|arXiv (Cornell University)|Feb 1, 2024

Astronomy and Astrophysical Research被引用 5

一句话总结

pop-cosmos 提出一个前向建模框架，并使用基于仿真的推断，从 COSMOS 光度测量中联合推断 galaxy 属性的完整联合分布，使用 SPS 模型及不确定性/选择性处理进行校准。

ABSTRACT

We present pop-cosmos: a comprehensive model characterizing the galaxy population, calibrated to $140,938$ ($r<25$ selected) galaxies from the Cosmic Evolution Survey (COSMOS) with photometry in $26$ bands from the ultra-violet to the infra-red. We construct a detailed forward model for the COSMOS data, comprising: a population model describing the joint distribution of galaxy characteristics and its evolution (parameterized by a flexible score-based diffusion model); a state-of-the-art stellar population synthesis (SPS) model connecting galaxies' instrinsic properties to their photometry; and a data-model for the observation, calibration and selection processes. By minimizing the optimal transport distance between synthetic and real data we are able to jointly fit the population- and data-models, leading to robustly calibrated population-level inferences that account for parameter degeneracies, photometric noise and calibration, and selection. We present a number of key predictions from our model of interest for cosmology and galaxy evolution, including the mass function and redshift distribution; the mass-metallicity-redshift and fundamental metallicity relations; the star-forming sequence; the relation between dust attenuation and stellar mass, star formation rate and attenuation-law index; and the relation between gas-ionization and star formation. Our model encodes a comprehensive picture of galaxy evolution that faithfully predicts galaxy colors across a broad redshift ($z<4$) and wavelength range.

研究动机与目标

• Characterize the joint distribution and evolution of galaxy properties using a large, deep COSMOS sample.
• Develop a forward model linking intrinsic galaxy properties to observed photometry via SPS and emission-line corrections.
• Calibrate photometry and uncertainties, and account for selection effects to enable unbiased population inferences.
• Apply simulation-based inference to jointly fit population and data-model parameters with robust handling of degeneracies.

提出的方法

• Use a score-based diffusion model to parameterize the population distribution P(phi, z | psi).
• Construct a forward model that connects SPS-generated rest-frame SEDs to observed photometry with emission-line corrections and dust attenuation.
• Incorporate zero-point calibration and emission-line corrections to SPS photometry, producing f_b(phi,z).
• Model photometric uncertainties with a mixture density network conditioned on flux, and include emission-line uncertainty contributions to the total noise.
• Add correlated noise via independent Student-t errors across bands and apply COSMOS-like selection to generate mock catalogs (D).
• Perform simulation-based inference by minimizing optimal transport distance W2 between observed and simulated catalogs to jointly constrain population and data-model parameters.

实验结果

研究问题

• RQ1 What is the joint, redshift-evolving distribution of galaxy properties in the COSMOS sample?
• RQ2 How do SPS, dust, emission lines, and AGN components shape the observed photometry across 26 bands?
• RQ3 Can forward-modeling with SBI recover unbiased population-level inferences accounting for photometric noise and selection effects?
• RQ4 What are the predicted relations and functions (e.g., mass function, mass-metallicity-redshift, star-forming sequence) implied by the calibrated population model?

主要发现

• A robustly calibrated population model (pop-cosmos) describing the joint distribution and evolution of galaxy properties from COSMOS data is obtained.
• The model yields predictions for the stellar mass function, redshift distribution, and the mass-metallicity-redshift and fundamental metallicity relations.
• It characterizes the star-forming sequence and the relation between dust attenuation, stellar mass, star formation rate, and attenuation-law index.
• The framework also constrains the gas-ionization and star-formation connection within galaxies across z < 4.