Lyα Halos And Accretion Flows In A High-Redshift Radio Galaxy At Z=3.pdf

Detecting Accretion Shocks in a 250 kpc Lyα Halo at z=3?

This manuscript presents deep integral-field spectroscopy of the high-redshift radio galaxy MRC 0316-257 using MUSE on ESO-VLT. The main findings include:

1. Extent and Morphology of Lyα Emission:

Detected Lyα emission out to approximately 250 kpc in projection from the active galactic nucleus (AGN).
The emission exhibits arc-like morphologies, with connected filamentary structures extending down into the circum-nuclear region.

2. Kinematic and Luminosity Analysis:

The most distant Lyα arcs are offset by ~700 km/s relative to circum-nuclear HeII λ1640 emission, suggesting a systemic velocity.
Line width ranges from 300-700 km/s as one moves closer to the nucleus, narrowing in projection on the sky.
High-speed (≳300 km/s) shocks into rare gas are proposed as a mechanism to explain the observed surface brightness of the extended emission.

3. Comparison with Simulations and Interpretation:

The Lyα morphology and surface brightness distribution resemble those predicted by simulations of gas accretion onto halos.
While the authors acknowledge potential for expectation bias, they find it instructive to compare their results with simulations.

4. Key Conclusions:

The study suggests that:

The observed Lyα arcs could represent accretion shocks into the halo.
* The filamentary emission may indicate gas flows into the halo.

Further analysis is needed to confirm these interpretations, but this work provides valuable insights into the complex interplay between AGN activity, halo gas, and galaxy evolution at high redshift.