Analytic models of dust temperature in high-redshift galaxies

Hiroyuki Hirashita; I-Da Chiang

doi:10.1093/mnras/stac2242

paper

Analytic models of dust temperature in high-redshift galaxies

arXiv:2208.04546 · doi:10.1093/mnras/stac2242

Abstract

We investigate physical reasons for high dust temperatures ( $T_{dust} ≳ 40$ K) observed in some high-redshift ( $z > 5$ ) galaxies using analytic models. We consider two models that can be treated analytically: the radiative transfer (RT) model, {where a broad distribution of values for $T_{dust}$ is considered}, and the one-tempearture (one- $T$ ) model, which assumes {uniform $T_{dust}$ }. These two extremes {serve to bracket the most realistic scenario}. We adopt the Kennicutt--Schmidt (KS) law to relate stellar radiation field to gas surface density, and vary the dust-to-gas ratio. As a consequence, our model is capable of predicting the relation between the surface density of star formation rate ( $Σ_{SFR}$ ) or dust mass ( $Σ_{dust}$ ) and $T_{dust}$ . We show that the high $T_{dust}$ observed at $z ≳ 5$ favour low dust-to-gas ratios ( $≲ 1 0^{- 3}$ ). An enhanced star formation compared with the KS law gives an alternative explanation for the high $T_{dust}$ . The dust temperatures are similar between the two (RT and one- $T$ ) models as long as we use ALMA Bands 6--8. We also examine the relation among $Σ_{SFR}$ , $Σ_{dust}$ and $T_{dust}$ without assuming the KS law, and confirm the consistency with the actual observational data at $z > 5$ . In the one- $T$ model, we also examine a clumpy dust distribution, which predicts lower $T_{dust}$ because of the leakage of stellar radiation. This enhances the requirement of low dust abundance or high star formation efficiency to explain the observed high $T_{dust}$ .

arXiv comment12 pages, 5 figures, Accepted for publication in MNRAS

Analytic models of dust temperature in high-redshift galaxies

Abstract

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