The Clustering Evolution of Dusty Star-Forming Galaxies

TL;DR

This paper predicts the clustering behavior of dusty star-forming galaxies at FIR and sub-millimetre wavelengths, incorporating effects of telescope resolution and comparing with observations to improve understanding of galaxy-halo connections.

Contribution

It introduces a new galaxy formation model that predicts galaxy clustering and dust emission, accounting for observational biases and matching observed clustering and background anisotropies.

Findings

Galaxies at 850 μm reside in halos of 10^{11.5}-10^{12} h^{-1} M_sun across redshifts.

Bright 850 μm galaxies at z~2.5 have a correlation length of ~5.5 h^{-1} Mpc, consistent with observations.

Confusion effects can overestimate halo masses by an order of magnitude in measurements.

Abstract

We present predictions for the clustering of galaxies selected by their emission at far infra-red (FIR) and sub-millimetre wavelengths. This includes the first predictions for the effect of clustering biases induced by the coarse angular resolution of single-dish telescopes at these wavelengths. We combine a new version of the GALFORM model of galaxy formation with a self-consistent model for calculating the absorption and re-emission of radiation by interstellar dust. Model galaxies selected at $850$ $\mu$m reside in dark matter halos of mass $M_{\rm halo}\sim10^{11.5}-10^{12}$ $h^{-1}$ M$_{\odot}$, independent of redshift (for $0.2\lesssim z\lesssim4$) or flux (for $0.25\lesssim S_{850\mu\rm m}\lesssim4$ mJy). At $z\sim2.5$, the brightest galaxies ($S_{850\mu\rm m}>4$ mJy) exhibit a correlation length of $r_{0}=5.5_{-0.5}^{+0.3}$ $h^{-1}$ Mpc, consistent with observations. We show that these galaxies have descendants with stellar masses $M_{\star}\sim10^{11}$ $h^{-1}$ M$_{\odot}$ occupying halos spanning a broad range in mass $M_{\rm halo}\sim10^{12}-10^{14}$ $h^{-1}$ M$_{\odot}$. The FIR emissivity at shorter wavelengths ($250$, $350$ and $500$ $\mu$m) is also dominated by galaxies in the halo mass range $M_{\rm halo}\sim10^{11.5}-10^{12}$ $h^{-1}$ M$_{\odot}$, again independent of redshift (for $0.5\lesssim z\lesssim5$). We compare our predictions for the angular power spectrum of cosmic infra-red background anisotropies at these wavelengths with observations, finding agreement to within a factor of $\sim2$ over all scales and wavelengths, an improvement over earlier versions of the model. Simulating images at $850$ $\mu$m, we show that confusion effects boost the measured angular correlation function on all scales by a factor of $\sim4$. This has important consequences, potentially leading to inferred halo masses being overestimated by an order of magnitude.