We present a study of Fe ii emission in the near-infrared region (NIR) for 25 active galactic nuclei (AGNs) to obtain information about the excitation mechanisms that power it and the location where it is formed. We employ a NIR Fe ii template derived in the literature and found that it successfully reproduces the observed Fe ii spectrum. The Fe ii bump at 9200Å detected in all objects studied confirms that Lyα fluorescence is always present in AGNs. The correlation found between the flux of the 9200Å bump, the 1 µm lines and the optical Fe ii imply that Lyα fluorescence plays an important role in the Fe ii production. We determined that at least 18% of the optical Fe ii is due to this process while collisional excitation dominates the production of the observed Fe ii. The line profiles of Fe ii λ10502, O i λ11287, Ca ii λ8664 and Paβ were compared to gather information about the most likely location where they are emitted. We found that Fe ii, O i and Ca ii have similar widths and are, on average, 30% narrower than Paβ. Assuming that the clouds emitting the lines are virialized, we show that the Fe ii is emitted in a region twice as far from the central source than Paβ. The distance though strongly varies: from 8.5 light-days for NGC 4051 to 198.2 light-days for Mrk 509. Our results reinforce the importance of the Fe ii in the NIR to constrain critical parameters that drive its physics and the underlying AGN kinematics as well as more accurate models aimed at reproducing this complex emission.

We report the discovery of the most distant radio galaxy to date, TGSS J1530+1049 at a redshift of z = 5.72, close to the presumed end of the Epoch of Reionisation. The radio galaxy was selected from the TGSS ADR1 survey at 150 MHz for having an ultra-steep spectral index, α 150 MHz 1.4 GHz = −1.4 and a compact morphology obtained using VLA imaging at 1.4 GHz. No optical or infrared counterparts for the radio source were found in publicly available sky surveys. Follow-up optical spectroscopy at the radio position using GMOS on Gemini North revealed the presence of a single emission line. We identify this line as Lyman alpha at z = 5.72, because of its asymmetric line profile, the absence of other optical/UV lines in the spectrum and a high equivalent width. With a Lyα luminosity of 5.7 × 10 42 erg s −1 and a FWHM of 370 km s −1 , TGSS J1530+1049 is comparable to 'non-radio' Lyman alpha emitters (LAEs) at a similar redshift. However, with a radio luminosity of log L 150 MHz = 29.1 W Hz −1 and a deconvolved physical size 3.5 kpc, its radio properties are similar to other known radio galaxies at z > 4. Subsequent J and K band imaging using LUCI on the Large Binocular Telescope resulted in non-detection of the host galaxy down to 3σ limits of J > 24.4 and K > 22.4 (Vega). The K band limit is consistent with z > 5 from the K − z relation for radio galaxies and helps rule out low redshifts. The stellar mass limit derived using simple stellar population models is M stars < 10 10.5 M . Its relatively low stellar mass and small radio and Lyα sizes suggest that TGSS J1530+1049 may be a radio galaxy in an early phase of its evolution.

We have obtained three-dimensional maps of the universe in ∼ 200×200×80 comoving Mpc 3 (cMpc 3 ) volumes each at z = 5.7 and 6.6 based on a spectroscopic sample of 179 galaxies that achieves 80% completeness down to the Lyα luminosity of log(L Lyα /[erg s −1 ]) = 43.0, based on our Keck and Gemini observations and the literature. The maps reveal filamentary large-scale structures and two remarkable overdensities made out of at least 44 and 12 galaxies at z = 5.692 (z57OD) and z = 6.585 (z66OD), respectively, making z66OD the most distant overdensity spectroscopically confirmed to date with > 10 spectroscopically confirmed galaxies. We compare spatial distributions of submillimeter galaxies at z 4 − 6 with our z = 5.7 galaxies forming the large-scale structures, and detect a 99.97% signal of cross correlation, indicative of a clear coincidence of dusty star-forming galaxy and dust unobscured galaxy formation at this early epoch. The galaxies in z57OD and z66OD are actively forming stars with star formation rates (SFRs) 5 times higher than the main sequence, and particularly the SFR density in z57OD is 10 times higher than the cosmic average at the redshift (a.k.a. the Madau-Lilly plot). Comparisons with numerical simulations suggest that z57OD and z66OD are protoclusters that are progenitors of the present-day clusters with halo masses of ∼ 10 14 M .