A 20 kiloparsec bipolar Lyman α outflow from a radio galaxy at z = 2.95

Puga, M. Coloma; Balmaverde, B.; Capetti, A.; Ramos Almeida, C.; Massaro, F.; Venturi, G.
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Astronomy and Astrophysics

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The study of ionized gas kinematics in high-z active galaxies plays a key part in our understanding of galactic evolution, in an age where nuclear activity was widespread and star formation close to its peak. We present a study of TXS 0952−217, a radio galaxy at z = 2.95, using VLT/MUSE integral field optical spectroscopy as part of a project aimed studying of the properties of ionized gas in high redshift radio galaxies (HzRGs). The Lyα line profile of this object presents various emission and absorption components. By utilizing Voronoi binning, we obtained a comprehensive map of the kinematic properties of these components. These observations revealed the presence of a redshifted, high velocity (v ∼ 500 km s−1) bipolar structure of Lyα emission, most likely corresponding to an outflow of ionized gas. The outflow extends beyond the compact radio source on both sides, with a total size of ∼21 kpc. Its kinetic power (1042.1 erg s−1) is about five orders of magnitude smaller than its radio power. Additional ionized lines, including HeIIλ1640, CIVλ1550 and CIII]λ1908 were detected and their line flux ratios determined. The presence of HeII allowed for a precise redshift measurement (z = 2.945 ± 0.002). Along with the recent discovery of a similar structure in TN J1049−1258, another HzRG, it displays the feasibility of using Lyα as a tracer of outflowing gas in high redshift sources, and particularly so when supported by non-resonant ionized lines such as HeII, which allow for accurate redshift and velocity measurements.