Lyman Break Galaxies, Lyalpha Emitters, and a Radio Galaxy in a Protocluster at z = 4.1
Résumé
We present deep HST ACS observations in g475r625i775z850 toward the z=4.1 radio galaxy TN J1338-1942 and its overdensity of >30 spectroscopically confirmed Lyalpha emitters (LAEs). We select 66 g475 band dropouts to z850,5sigma=27, 6 of which are also LAEs. Although our color-color selection results in a relatively broad redshift range centered on z=4.1, the field of TN J1338-1942 is richer than the average field at the >5 sigma significance, based on a comparison with GOODS. The angular distribution is filamentary with about half of the objects clustered near the radio galaxy, and a small, excess signal (2 sigma) in the projected pair counts at separations of theta1014 Msolar structure, confirming that it is possible to find and study cluster progenitors in the linear regime at z>~4.