[OIII] emitters in the field of the MRC 0316-257 protocluster

TL;DR

This study identifies and characterizes [O III] emitters in a high-redshift protocluster, revealing galaxy properties, dynamics, and evidence of active galactic nuclei within a forming large-scale structure.

Contribution

It presents the first infrared narrow-band imaging survey of [O III] emitters in a protocluster, confirming new members and analyzing their properties and kinematics.

Findings

Thirteen [O III] candidates detected, with some confirmed by spectroscopy.

The confirmed galaxies are within a few hundred km/s, blueshifted relative to the radio galaxy.

Evidence suggests some galaxies host AGN, influencing their ionization.

Abstract

Venemans et al. (2005) found evidence for an overdensity of Ly-alpha emission line galaxies associated with the radio galaxy MRC 0316-257 at z=3.13 indicating the presence of a massive protocluster. Here, we present the results of a search for additional star-forming galaxies and AGN within the protocluster. Narrow-band infrared imaging was used to select candidate [O III] emitters in a 1.1 x 1.1 Mpc^2 region around the radio galaxy. Thirteen candidates have been detected. Four of these are among the previously confirmed sample of Ly-alpha galaxies, and an additional three have been confirmed through follow-up infrared spectroscopy. The three newly confirmed objects lie within a few hundred km/s of each other, but are blueshifted with respect to the radio galaxy and Ly-alpha emitters by ~2100 km/s. Although the sample is currently small, our results indicate that the radio-selected protocluster is forming at the centre of a larger, ~60 co-moving Mpc super-structure. On the basis of an HST/ACS imaging study we calculate dust-corrected star-formation rates and investigate morphologies and sizes of the [O III] candidate emitters. From a comparison of the star formation rate derived from UV-continuum and [O III] emission, we conclude that at least two of the [O III] galaxies harbour an AGN which ionized the O+ gas.