Cosmic Sands. II. Challenges in Predicting and Measuring High-z Dust Temperatures

Abstract

In the current era of high-z galaxy discovery with JWST and the Atacama Large Millimeter/submillimeter Array, our ability to study the stellar populations and interstellar medium conditions in a diverse range of galaxies at Cosmic Dawn has rapidly improved. At the same time, the need to understand the current limitations in modeling galaxy formation processes and physical properties in order to interpret these observations is critical. Here, we study the challenges in modeling galaxy dust temperatures, both in the context of forward modeling galaxy spectral properties from a hydrodynamical simulation and via backwards modeling galaxy physical properties from mock observations of far-infrared dust emission. Using the simba model for galaxy formation combined with powderday radiative transfer, we can accurately predict the evolution of dust at high redshift, though several aspects of the model are essentially free parameters (dust composition, subresolution dust in star-forming regions) that dull the predictive power of the model dust temperature distributions. We also highlight the uncertainties in the backwards modeling methods, where we find the commonly used models and assumptions to fit far-infrared spectral energy distributions and infer dust temperatures (e.g., single temperature, optically thin modified blackbody) largely fail to capture the complexity of high-z dusty galaxies. We caution that conclusions inferred from both simulations—limited by resolution and post-processing techniques—and observations—limited by sparse data and simplistic model parameterizations—are susceptible to unique and nuanced uncertainties that can limit the usefulness of current high-z dust measurements.

Modeling Dust Production, Growth, and Destruction in Reionization-era Galaxies with the CROC Simulations. II. Predicting the Dust Content of High-redshift Galaxies

“…The rest-frame IR luminosity from each cell is calculated as a modified blackbody (i.e., in the optically thin limit) L λ = 4πM D κ D B λ (T D ) where M D is the dust mass, κ D is the same SMC (Weingartner & Draine 2001) opacity law assumed for the UV quantities, and B λ (T D ) is a blackbody of dust temperature T D . Since the calculation of the dust temperature is extremely complicated and relies on many other uncertain parameters such as the material properties of the dust grains (see, e.g., Lower et al 2024), we simply assume T D = 40 K throughout. See Esmerian & Gnedin (2022) for the effects of varying this parameter.…”