Translators of galaxy morphology indicators between observation and simulation

TL;DR

This paper compares observational and simulation-based galaxy morphology indicators using high-resolution simulations and mock observations, revealing which indicators accurately reflect true galaxy structures.

Contribution

It introduces a method to translate between different galaxy morphology indicators and assesses their effectiveness in representing true galaxy structures.

Findings

Spectroscopic indicators like V/σ and λ_R closely match kinematic ratios.

Photometric ratios often fail to recover true structures, especially in small galaxies.

Provides equations to translate between various morphological indicators.

Abstract

Based on the recent advancements in the numerical simulations of galaxy formation, we anticipate the achievement of realistic models of galaxies in the near future. Morphology is the most basic and fundamental property of galaxies, yet observations and simulations still use different methods to determine galaxy morphology, making it difficult to compare them. We hereby perform a test on the recent NewHorizon simulation which has spatial and mass resolutions that are remarkably high for a large-volume simulation, to resolve the situation. We generate mock images for the simulated galaxies using SKIRT that calculates complex radiative transfer processes in each galaxy. We measure morphological indicators using photometric and spectroscopic methods following observer's techniques. We also measure the kinematic disk-to-total ratios using the Gaussian mixture model and assume that they represent the true structural composition of galaxies. We found that spectroscopic indicators such as $V/{\sigma}$ and ${\lambda}_{R}$ closely trace the kinematic disk-to-total ratios. In contrast, photometric disk-to-total ratios based on the radial profile fitting method often fail to recover the true kinematic structure of galaxies, especially for small galaxies. We provide translating equations between various morphological indicators.