We investigate the ionised gas kinematics , physical properties and chemical abundances of SDSS J 142947 , a Green Pea galaxy at redshift z \sim 0.17 with strong , double-peak Ly \alpha emission and indirect evidence of Lyman continuum ( LyC ) leakage .
Using high-dispersion spectroscopy , we perform a multi-component analysis of emission-line profiles .
Our model consistently fits all lines as a narrow component with intrinsic velocity dispersion \sigma \sim 40 km s ^ { -1 } , and two broader blue-shifted components with \sigma \sim 90 km s ^ { -1 } and \sim 250 km s ^ { -1 } .
We find electron densities and temperatures , ionisation conditions , and direct O/H and N/O abundances for each component .
A highly ionised , metal-poor , young and compact starburst dominates narrow emission , showing evidence of hard radiation fields and elevated N/O .
The blue-shifted broader components are consistent with highly turbulent , possibly clumpy ionised gas at the base of a strong photoionised outflow , which accounts for \gtrsim 50 % of the integrated emission-line fluxes .
The outflow is dense and metal-enriched compared to the H ii regions , with expansion velocities larger than those obtained from UV interstellar absorption lines under standard assumptions .
Some of these metals may be able to escape , with outflows loading factors comparable to those found in high- z galaxies of similar SFR/Area .
Our findings depict a two-stage starburst picture ; hard radiation fields from young star clusters illuminate a turbulent and clumpy ISM that has been eroded by SNe feedback .
While UV data suggest an extended Ly \alpha halo with high average H i column density , LyC photons could only escape from SDSS J 142947 through low H i density channels or filaments in the ISM approaching density-bounded conditions , traced by outflowing gas .