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Centro de Astrofísica da Universidade do Porto

MUSE 3D Spectroscopy and Kinematics of the gigahertz peaked spectrum Radio Galaxy PKS 1934-63: Interaction, Recently Triggered AGN and Star Formation

N. Roche, A. Humphrey, P. Lagos, P. Papaderos, M. S. Silva, L. S. M. Cardoso, J. M. Gomes


We observe the radio galaxy PKS 1934-63 (at z=0.1825) using MUSE (Multi Unit Spectroscopic Explorer) on the Very Large Telescope (VLT). The radio source is GigaHertz Peaked Spectrum and compact (0.13 kpc), implying an early stage of evolution (≤104 yr). Our data show an interacting pair of galaxies, projected separation 9.1 kpc, velocity difference Δ(v)=216 km s−1. The larger galaxy is a M∗≃1011M⊙ spheroidal with the emission-line spectrum of a high-excitation young radio AGN, e.g. strong [OI]6300 and [OIII]5007. Emission-line ratios indicate a large contribution to the line luminosity from high-velocity shocks (≃550 km s−1) . The companion is a non-AGN disk galaxy, with extended Hα emission from which its star-formation rate is estimated as 0.61 M⊙yr−1. 
Both galaxies show rotational velocity gradients in Hα and other lines, with the interaction being prograde-prograde. The SE-NW velocity gradient of the AGN host is misaligned from the E-W radio axis, but aligned with a previously discovered central ultraviolet source, and a factor 2 greater in amplitude in Hα than in other (forbidden) lines (e.g. [OIII]5007). This could be produced by a fast rotating (100-150 km s−1) disk with circumnuclear star-formation. We also identify a broad component of [OIII]5007 emission, blueshifted with a velocity gradient aligned with the radio jets, and associated with outflow. However, the broad component of [OI]6300 is redshifted. In spectral fits, both galaxies have old stellar populations plus ∼0.1% of very young stars, consistent with the galaxies undergoing first perigalacticon, triggering infall and star-formation from ∼40 Myr ago followed by the radio outburst.

Monthly Notices of the Royal Astronomical Society
Volume 459, Page 4259
April 2016

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