The far infra-red SEDs of main sequence and starburst galaxies

TL;DR

This study compares observed far-infrared/sub-millimetre galaxy spectral energy distributions with predictions from a new galaxy formation model, finding good agreement for main sequence galaxies across a wide redshift range and insights into dust temperature evolution.

Contribution

The paper introduces a self-consistent model for galaxy FIR SEDs based on radiative transfer and energy balance, and compares it with observations to validate its predictions.

Findings

Good agreement between model and observed SEDs for main sequence galaxies from z~0.5 to 4.

Model predicts larger scatter in sSFR at higher masses and redshifts.

Dust temperature evolution is driven by star formation activity being more burst-like at higher redshifts.

Abstract

We compare observed far infra-red/sub-millimetre (FIR/sub-mm) galaxy spectral energy distributions (SEDs) of massive galaxies ($M_{\star}\gtrsim10^{10}$ $h^{-1}$M$_{\odot}$) derived through a stacking analysis with predictions from a new model of galaxy formation. The FIR SEDs of the model galaxies are calculated using a self-consistent model for the absorption and re-emission of radiation by interstellar dust based on radiative transfer calculations and global energy balance arguments. Galaxies are selected based on their position on the specific star formation rate (sSFR) - stellar mass ($M_{\star}$) plane. We identify a main sequence of star-forming galaxies in the model, i.e. a well defined relationship between sSFR and $M_\star$, up to redshift $z\sim6$. The scatter of this relationship evolves such that it is generally larger at higher stellar masses and higher redshifts. There is remarkable agreement between the predicted and observed average SEDs across a broad range of redshifts ($0.5\lesssim z\lesssim4$) for galaxies on the main sequence. However, the agreement is less good for starburst galaxies at $z\gtrsim2$, selected here to have elevated sSFRs$>10\times$ the main sequence value. We find that the predicted average SEDs are robust to changing the parameters of our dust model within physically plausible values. We also show that the dust temperature evolution of main sequence galaxies in the model is driven by star formation on the main sequence being more burst-dominated at higher redshifts.