Linking galaxies to dark matter haloes at $zsim1$ : dependence of galaxy clustering on stellar mass and specific star formation rate

We study the dependence of angular two-point correlation functions on stellar mass ($M_{*}$) and specific star formation rate (sSFR) of $M_{*}>10^{10}M_{odot}$ galaxies at $zsim1$. The data from UKIDSS DXS and CFHTLS covering 8.2 deg$^{2}$ sample scales larger than 100 $h^{-1}$Mpc at $zsim1$, allowing us to investigate the correlation between clustering, $M_{*}$, and star formation through halo modeling. Based on halo occupation distributions (HODs) of $M_{*}$ threshold samples, we derive HODs for $M_{*}$ binned galaxies, and then calculate the $M_{*}/M_{rm halo}$ ratio. The ratio for central galaxies shows a peak at $M_{rm halo}sim10^{12}h^{-1}M_{odot}$, and satellites predominantly contribute to the total stellar mass in cluster environments with $M_{*}/M_{rm halo}$ values of 0.01--0.02. Using star-forming galaxies split by sSFR, we find that main sequence galaxies ($rm log,sSFR/yr^{-1}sim-9$) are mainly central galaxies in $sim10^{12.5} h^{-1}M_{odot}$ haloes with the lowest clustering amplitude, while lower sSFR galaxies consist of a mixture of both central and satellite galaxies where those with the lowest $M_{*}$ are predominantly satellites influenced by their environment. Considering the lowest $M_{rm halo}$ samples in each $M_{*}$ bin, massive central galaxies reside in more massive haloes with lower sSFRs than low mass ones, indicating star-forming central galaxies evolve from a low $M_{*}$--high sSFR to a high $M_{*}$--low sSFR regime. We also find that the most rapidly star-forming galaxies ($rm log,sSFR/yr^{-1}>-8.5$) are in more massive haloes than main sequence ones, possibly implying galaxy mergers in dense environments are driving the active star formation. These results support the conclusion that the majority of star-forming galaxies follow secular evolution through the sustained but decreasing formation of stars.

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 $zsim1$. 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 $zsim1.1$, at $zsim1.5$ 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.

Clustering properties of high redshift red galaxies in SA22 from the UKIDSS DXS

Deep, wide, near-infrared imaging surveys provide an opportunity to study the clustering of various galaxy populations at high redshift on the largest physical scales. We have selected $1<z<2$ extremely red objects (EROs) and $1<z<3$ distant red galaxies (DRGs) in SA22 from the near-infrared photometric data of the UKIDSS Deep eXtragalactic Survey (DXS) and $gri$ optical data from CTIO covering 3.3~deg$^2$. This is the largest contiguous area studied to sufficient depth to select these distant galaxies to date. The angular two-point correlation functions and the real space correlation lengths of each population are measured and show that both populations are strongly clustered and that the clustering cannot be parameterised with a single power law. The correlation function of EROs shows a double power law with the inflection at $sim$ 0.6$$--1.2$$ (0.6--1.2~h$^{-1}$~Mpc). The bright EROs ($K<18.8$) show stronger clustering on small scales but similar clustering on larger scales, whereas redder EROs show stronger clustering on all scales. Clustering differences between EROs that are old passively evolved galaxies (OGs) and dusty star-forming galaxies (DGs), on the basis of their $J-K$ colour, are also investigated. The clustering of $r-K$ EROs are compared with that of $i-K$ EROs and the differences are consistent with their expected redshift distributions. The correlation function of DRGs is also well described by a double power law and consistent with previous studies once the effects of the broader redshift distribution our selection of DRGs returns are taken into account. We also perform the same analysis on smaller sub-fields to investigate the impact of cosmic variance on the derived clustering properties. Currently this study is the most representative measurement of the clustering of massive galaxies at $z>1$ on large scales.