Emission-line Wings Driven by Lyman Continuum in the Green Pea Analog Mrk 71

TL;DR

This paper investigates the origin of broad emission-line wings in Mrk 71, attributing them to a radiation-driven superwind powered by Lyman continuum and Lyα radiation, revealing a radiation-dominated environment with high-velocity outflows.

Contribution

It introduces a model where clumpy, radiation-driven superwinds explain extreme emission-line wings in Green Pea analogs, emphasizing the role of LyC and Lyα opacity in wind acceleration.

Findings

Broad wings originate from super star cluster Knot A.

Radiation pressure dominates over gas pressure in the environment.

Power-law fits suggest a common wind-acceleration mechanism.

Abstract

We propose that the origin of faint, broad emission-line wings in the Green Pea (GP) analog Mrk 71 is a clumpy, LyC and/or Ly$\alpha$-driven superwind. Our spatially-resolved analysis of Gemini-N/GMOS-IFU observations shows that these line wings with terminal velocity $>3000~\rm{km~s^{-1}}$ originate from the super star cluster (SSC) Knot A, and propagate to large radii. The object's observed ionization parameter and stellar surface density are close to their theoretical maxima, and radiation pressure dominates over gas pressure. Together with a lack of evidence for supernova feedback, these imply a radiation-dominated environment. We demonstrate that a clumpy, radiation-driven superwind from Knot A is a viable model for generating the extreme velocities, and in particular, that Lyman continuum and/or Ly$\alpha$ opacity must be responsible. We find that the Mrk 71 broad wings are best fitted with power laws, as are those of a representative extreme GP and a luminous blue variable star, albeit with different slopes. This suggests that they may share a common wind-acceleration mechanism. We propose that high-velocity, power-law wings may be a distinctive signature of radiation feedback, and of radiatively-driven winds, in particular.