The clustering and bias of radio-selected AGN and star-forming galaxies
  in the COSMOS field
  Dark matter haloes in which galaxies reside are likely to have a significant
impact on their evolution. We investigate the link between dark matter haloes
and their constituent galaxies by measuring the angular two-point correlation
function of radio sources, using recently released 3 GHz imaging over $\sim 2 \
\mathrm{deg}^2$ of the COSMOS field. We split the radio source population into
Star Forming Galaxies (SFGs) and Active Galactic Nuclei (AGN), and further
separate the AGN into radiatively efficient and inefficient accreters.
Restricting our analysis to $z<1$, we find SFGs have a bias, $b = 1.5
^{+0.1}_{-0.2}$, at a median redshift of $z=0.62$. On the other hand, AGN are
significantly more strongly clustered with $b = 2.1\pm 0.2$ at a median
redshift of 0.7. This supports the idea that AGN are hosted by more massive
haloes than SFGs. We also find low-accretion rate AGN are more clustered ($b =
2.9 \pm 0.3$) than high-accretion rate AGN ($b = 1.8^{+0.4}_{-0.5}$) at the
same redshift ($z \sim 0.7$), suggesting that low-accretion rate AGN reside in
higher mass haloes. This supports previous evidence that the relatively hot gas
that inhabits the most massive haloes is unable to be easily accreted by the
central AGN, causing them to be inefficient. We also find evidence that
low-accretion rate AGN appear to reside in halo masses of $M_{h} \sim 3-4
\times 10^{13}h^{-1}$M$_{\odot}$ at all redshifts. On the other hand, the
efficient accreters reside in haloes of $M_{h} \sim 1-2 \times
10^{13}h^{-1}$M$_{\odot}$ at low redshift but can reside in relatively lower
mass haloes at higher redshifts. This could be due to the increased prevalence
of cold gas in lower mass haloes at $z \ge 1$ compared to $z<1$.
