Integral field spectroscopy of two radio galaxies at z ∼ 2.3

Aims. In this article we study the morphology, kinematics and ionization properties of the giant ionized gas nebulae surrounding two high redshift radio galaxies, 4C 40.36 (z = 2.27) and 4C 48.48 (z = 2.34). Methods. Integral field spectroscopy observations were taken using the PPAK bundle of the PMAS spectrograph, mounted on the 3.5 m on the Calar Alto Observatory, in order to cover a field-of-view of 64 '' x 72 '' centered in each radio galaxy. The observations spanned 5 nights, using two different spectral resolutions (with FWHM similar to 4 angstrom and similar to 8 angstrom respectively), covering the optical wavelength range from similar to 3700 angstrom to similar to 7100 angstrom, which corresponds to the rest-frame ultraviolet range from similar to 1100 angstrom to similar to 2000 angstrom. Various emission lines are detected within this wavelength range, including Ly alpha (1216 angstrom), NV (1240 angstrom), CIV (1549 angstrom), HeII (1640 angstrom), OIII] (1663 angstrom) and CIII] (1909 angstrom). The dataset was used to derive the spatial distribution of the flux intensity of each of these lines and the gas kinematics. The properties of the emission lines in the nuclear regions were studied in detail. Results. In agreement with previous studies, we find that both objects are embedded in a large ionized gas nebula, where Lya emission is extended across similar to 100 kpc or more. The CIV and HeII emission lines are also spatially extended. The nebulae are generally aligned with the radio axis, although we detect emission far from it. In 4C+ 48.48, there is a band of low Ly alpha/ CIV running perpendicular to the radio axis, at the location of the active nucleus. This feature might be the observational signature of an edge- on disk of neutral gas. The kinematics of both nebulae are inconsistent with stable rotation, although they are not inconsistent with infall or outflow.