A Star-Forming Shock Front in Radio Galaxy 4C+41.17 Resolved with Laser-Assisted Adaptive Optics Spectroscopy

TL;DR

This study uses laser-assisted adaptive optics spectroscopy to resolve a star-forming shock front in a high-redshift radio galaxy, revealing detailed nebular emission and kinematics linked to jet activity and star formation regions.

Contribution

First high-resolution near-infrared integral-field spectroscopy of z=3.8 radio galaxy 4C+41.17, providing detailed spatial, spectral, and kinematic insights into jet-induced star formation.

Findings

Resolved nebular emission associated with the jet

Identified a bow shock structure inducing star formation

Mapped kinematic and diagnostic line information

Abstract

Near-infrared integral-field spectroscopy of redshifted [O III], H-beta and optical continuum emission from z=3.8 radio galaxy 4C+41.17 is presented, obtained with the laser-guide-star adaptive optics facility on the Gemini North telescope. Employing a specialized dithering technique, a spatial resolution of 0.10 arcsec or 0.7 kpc is achieved in each spectral element, with velocity resolution of ~70 km/s. Spectra similar to local starbursts are found for bright knots coincident in archival Hubble Space Telescope (HST) restframe-ultraviolet images, which also allows a key line diagnostic to be mapped together with new kinematic information. There emerges a clearer picture of the nebular emission associated with the jet in 8.3 GHz and 15 GHz Very Large Array maps, closely tied to a Ly-alpha-bright shell-shaped structure seen with HST. This supports a previous interpretation of that arc tracing a bow shock, inducing 10^10-11 M_solar star-formation regions that comprise the clumpy broadband optical/ultraviolet morphology near the core.