Sub-millimetre galaxies in cosmological hydrodynamic simulations: Source number counts and the spatial clustering

TL;DR

This study uses cosmological hydrodynamic simulations to model sub-millimetre galaxies, successfully reproducing observed number counts and clustering, and predicts the existence of numerous faint SMGs at high redshifts detectable by ALMA.

Contribution

The paper presents a self-consistent simulation-based model that reproduces observed SMG properties and provides new predictions for high-redshift SMG populations.

Findings

Model reproduces submm source counts and clustering amplitude.

Bright SMGs reside in halos of about 10^13 solar masses.

Hundreds of SMGs with flux >0.1 mJy exist at z > 5 per square degree.

Abstract

We use large cosmological Smoothed-Particle-Hydrodynamics simulations to study the formation and evolution of sub-millimetre galaxies (SMGs). In our previous work, we studied the statistical properties of ultra-violet selected star-forming galaxies at high redshifts. We populate the same cosmological simulations with SMGs by calculating the reprocess of stellar light by dust grains into far-infrared to millimetre wavebands in a self-consistent manner. We generate light-cone outputs to compare directly the statistical properties of the simulated SMGs with available observations. Our model reproduces the submm source number counts and the clustering amplitude. We show that bright SMGs with flux $S > 1$ mJy reside in halos with mass of $\sim 10^{13} M_{\odot}$ and have stellar masses greater than $10^{11}\sim \rm M_{\odot}$. The angular cross-correlation between the SMGs and Lyman-$\alpha$ emitters is significantly weaker than that between the SMGs and Lyman-break galaxies. The cross-correlation is also weaker than the auto-correlation of the SMGs. The redshift distribution of the SMGs shows a broad peak at $z \sim 2$, where Bright SMGs contribute significantly to the global cosmic star formation rate density. Our model predicts that there are hundreds of SMGs with $S > 0.1$ mJy at $z > 5$ per 1 square degree field. Such SMGs can be detected by ALMA.