[论文解读] Spatially resolved stellar-to-total dynamical mass relation: Radial variations, gradients and profiles of galaxy stellar populations

L. Scholz-Diaz, A. R. Gallazzi+2 more|arXiv (Cornell University)|Jan 22, 2026

Galaxies: Formation, Evolution, Phenomena被引用 0

一句话总结

该研究使用 CALIFA IFS 数据绘制在恒星到总动态质量关系（STDMR）上的空间分辨恒星年龄与金属丰度分布，揭示与恒星质量/总质量及形态相关的径向依赖与梯度。

ABSTRACT

Although galaxy evolution is governed by the interplay between baryonic physics and dark matter halo assembly, how halo properties shape observed galaxies remains unclear. With current challenges in measuring halo properties, the stellar-to-total dynamical mass relation is introduced as an alternative metric sensitive to the dark matter content within galaxies. We explore how spatially resolved stellar population properties vary across this relation using optical IFS data and photometry from 265 CALIFA galaxies. Spatially resolved ages and metallicities, [M/H], are derived using a Bayesian framework fed with a library of model spectra based on stochastic star formation and metallicity histories and dust attenuation. We study these properties in terms of both stellar and total dynamical mass, with the latter being enclosed mass within three effective radii from Jeans dynamical modeling. We find that ages and [M/H] measured at different annuli depend on both stellar and total mass, yet showing distinct radial trends. While the dependence of age on total mass is more prominent in the outskirts, that of [M/H] is significant in the inner parts. This behavior is reflected in the stellar population profiles and gradients, more strongly for age and connected to morphology. Intermediate-mass early-types have higher stellar-to-total mass ratios and flatter age profiles with older ages, and steep negative [M/H] profiles, whereas later-types have lower stellar-to-total mass ratios, negative age profiles with younger ages and shallower negative [M/H] profiles. Moreover, at fixed stellar mass galaxies have more negative age gradients and shallower [M/H] ones as total mass increases. Our results show that total dynamical mass is linked to systematic variations in stellar populations and radial gradients at fixed stellar mass, suggesting a relevant role of dark matter halos in shaping galaxy properties

研究动机与目标

• Investigate how spatially resolved stellar population properties vary across the stellar-to-total dynamical mass relation (STDMR).
• Quantify radial variations in ages and metallicities within different galactocentric annuli.
• Assess how inner and outer stellar population gradients relate to stellar mass and total dynamical mass.
• Explore how profiles depend on morphological type and relate to halo assembly histories.

提出的方法

• Analyze optical integral-field spectroscopic data from the CALIFA survey for a sample of 265 galaxies.
• Derive spatially resolved ages and metallicities via a Bayesian fitting framework with a large library of model spectra.
• Obtain total dynamical masses within 3 effective radii from detailed Jeans dynamical modeling of stellar kinematics.
• Use adaptive smoothing to reach target SNR, preserving spatial information while ensuring robust stellar population inferences.
• Employ partial correlation analysis to disentangle dependencies of stellar population properties on stellar mass and total mass.

Figure 1: Stellar-to-total dynamical mass relation for our CALIFA galaxies in terms of stellar population properties measured at different annul. Each column corresponds to a different annulus with increasing galactocentric distance from left to right (see text). Galaxies are shown as circles colore

实验结果

研究问题

• RQ1 How do median stellar ages and metallicities at different galactocentric radii depend on stellar mass and total dynamical mass?
• RQ2 What are the radial gradients of age and metallicity across the STDMR, and how do they vary with mass and morphology?
• RQ3 Do inner and outer stellar population properties show different dependencies on M★ and Mtot, and how is the STDMR scatter connected to stellar population gradients?
• RQ4 How do the observed radial trends relate to galaxy morphology and implied halo assembly histories?

主要发现

• Ages depend on both stellar mass and total mass, with a stronger dependence on stellar mass and a secondary anti-correlation with total mass, increasingly evident from inner to outer regions.
• Metallicity [M/H] in the inner regions mirrors the integrated 1 R_e trends, mainly depending on stellar mass with a weaker, sometimes significant, dependence on total mass that diminishes with radius.
• Outer regions show reduced correlations with total mass, and metallicity gradients become weaker at larger radii.
• Stellar population gradients (age and metallicity) vary across the STDMR and correlate with mass, morphology, and inferred halo assembly histories, e.g., intermediate-mass early-types having higher STDMR and flatter age profiles but steeper negative [M/H] gradients, while later-types have lower STDMR, negative age gradients, and less steep metallicity gradients.
• The scatter in the STDMR is connected to differences in stellar population gradients, particularly for age.
• Overall, total dynamical mass at fixed stellar mass associates with systematic changes in the radial stellar populations, suggesting halos influence galaxy properties.

Figure 2: Stellar population gradients across the stellar-to-total dynamical mass relation. Galaxies are shown as circles colored-coded by age gradient, $\nabla\log\rm Age$ , (upper panels), and metallicity gradient, $\nabla\rm[M/H]$ , (lower panels). Inner gradient (left panels), outer gradient (mi