http://arxiv.org/abs/1403.5924
We present wide-field Lya imaging observations of the field around TN J1338-1942, a powerful radio galaxy associated with an extended Lya nebula (>100 kpc) at z=4.11, with Subaru Prime-focus Camera to probe the environment of the radio galaxy. We used a sample of Lya emitters (LAEs) down to the Lya luminosity of $\log(L_{\rm Lya}\rm [erg\, s^{-1}])\sim 42.8$ to measure the galaxy density of this field, calibrating by direct comparison with a control sample in a blank field taken with the same instrument. We found that the radio galaxy resides in a region with a peak overdensity of $\delta_{\rm LAE}=3.1\pm 0.5$, after being smoothed on $8\, h^{-1}$ Mpc scales on the sky and $160\, h^{-1}$ Mpc along the line of sight (both in comoving coordinates). Adjacent to this overdense region, we found a highly underdense region where virtually no LAEs are detected. We used a semi-analytical model of LAEs derived from the Millennium Simulation to compare our results with theoretical predictions. This comparison suggests that, while the density distribution of the simulation is consistent with that of the blank field, overdense regions such as the one found in the radio galaxy field are very rare, with the number density of $2\times 10^{-7}h^{3}$ Mpc$^{-3}$ (comoving), corresponding to the densest <0.1 percentile at these redshifts. We also found a difference in the Lya luminosity function in the radio galaxy field compared with the blank field: the number of bright LAEs ($\log(L_{\rm Lya}\rm [erg\, s^{-1}])<43.3$) is enhanced, while the number of fainter LAEs is relatively suppressed. These results suggest that some powerful radio galaxies associated with Lya nebulae reside in extreme overdensities on $\sim 10-20\, h^{-1}$ Mpc scales, where star-formation and AGN activities may be enhanced via more frequent galaxy mergers or higher rates of gas accretion from the surroundings.
T. Saito, Y. Matsuda, C. Lacey, et. al.
Tue, 25 Mar 14
32/79
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