Clustering of Extremely Red Objects in Elais-N1 from the UKIDSS DXS with
  optical photometry from Pan-STARRS1 and Subaru
  We measure the angular clustering of 33 415 extremely red objects (EROs) in
the Elais-N1 field covering 5.33 deg$^{2}$, which cover the redshift range
$z=0.8$ to $2$. This sample was made by merging the UKIDSS Deep eXtragalactic
Survey (DXS) with the optical Subaru and Pan-STARRS PS1 datasets. We confirm
the existence of a clear break in the angular correlation function at $\sim
0.02^{\circ}$ corresponding to $1 h^{-1}$ Mpc at $z\sim1$. We find that redder
or brighter EROs are more clustered than bluer or fainter ones. Halo Occupation
Distribution (HOD) model fits imply that the average mass of dark matter haloes
which host EROs is over $10^{13} h^{-1} M_{\odot}$ and that EROs have a bias
ranging from 2.7 to 3.5. Compared to EROs at $z\sim1.1$, at $z\sim1.5$ EROs
have a higher bias and fewer are expected to be satellite galaxies.
Furthermore, EROs reside in similar dark matter haloes to those that host
$10^{11.0} M_{\odot}<M_{*}<10^{11.5} M_{\odot}$ galaxies. We compare our new
measurement and HOD fits with the predictions of the GALFORM semi-analytical
galaxy formation model. Overall, the clustering predicted by GALFORM gives an
encouraging match to our results. However, compared to our deductions from the
measurements, GALFORM puts EROs into lower mass haloes and predicts that a
larger fraction of EROs are satellite galaxies. This suggests that the
treatment of gas cooling may need to be revised in the model. Our analysis
illustrates the potential of clustering analyses to provide observational
constraints on theoretical models of galaxy formation.
