Realistic multitemperature dust: How well can we constrain the dust properties of high-redshift galaxies?

Abstract

Determining the dust properties of high-redshift galaxies from their far-infrared continuum emission is challenging due to limited multifrequency data. As a result, the dust spectral energy distribution (SED) is often modelled as a single-temperature modified blackbody. We assess the accuracy of the single-temperature approximation by constructing realistic dust SEDs using a physically motivated prescription where the dust temperature probability distribution function (PDF) is described by a skewed normal distribution. This approach captures the complexity of the mass-weighted and luminosity-weighted temperature PDFs of simulated galaxies and quasars, and yields far-infrared SEDs that match high-redshift observations. We explore how varying the mean temperature (), width, and skewness of the temperature PDF affects the recovery of the dust mass, infrared (IR) luminosity, and dust emissivity index () at. Fitting the dust SEDs with a single-temperature approximation, we find that dust masses are generally well recovered, although they may be underestimated by up to for broad temperature distributions with a low, as seen in some high-redshift quasars and/or evolved galaxies. IR luminosities are generally recovered within the uncertainty (dex), except at K, where the peak shifts well beyond ALMA's wavelength coverage. The inferred dust emissivity index is consistently shallower than the input one () due to the effect of multitemperature dust, suggesting that a steep may probe dust composition and grain size variations. With larger galaxy samples and well-sampled dust SEDs, systematic errors from multitemperature dust may dominate over fitting uncertainties and should thus be considered.