Nitrogen enrichment through stellar chemical feedback at parsec scale in NGC 5253 as seen with MUSE–NFM

ABSTRACT NGC 5253 is a nearby (D = 3.6 Mpc) Blue Compact Dwarf galaxy, notable for its three massive young super star clusters (SSCs) and nitrogen enrichment. Its similarity to extreme star-forming galaxies at high redshift makes it a good local analogue for studying chemical enrichment at high spatial resolution. We characterize the ionized gas and dust in the giant H ii region in the proximity of the three SSCs in the centre of NGC 5253 using new Multi-Unit Spectroscopic Explorer Narrow Field Mode adaptive optics-assisted data at unprecedented spatial resolution of 0${_{.}^{\prime\prime}}$15 ($\sim$2.3 pc). We derive the attenuation for the central SSCs and, for the first time, map the extinction parameter ($R_V$) in an extragalactic object. $R_V$ varies among SSCs, suggesting differences in dust physics. Electron temperature and density diagnostics yield flat temperature distributions $T_\mathrm{e,median}$([N ii])$=12000 \pm 1700$ K and $T_\mathrm{e,median}$([S iii])$= 11\,000 \pm 600$ K, and a structured $n_e$([S ii]) of maximum $1930 \pm 40$ cm$^{-3}$. The direct method gives a flat helium abundance ($10^3y^+ = 81 \pm 4$) and uniform oxygen abundance ($12 + \log (\text{O/H}) = 8.22 \pm 0.05$). N/O shows a factor 2–3 enhancement around the SSCs, mapped here for the first time at such high spatial resolution. The total excess nitrogen mass is $\sim$0.3 $\mathrm{ M}_\odot$, which we estimate is producible by the observed WN-type Wolf–Rayet (WR) stars. Since there is no direct spatial overlap between the enrichment and WR star positions, the N-rich material appears to have been expelled from the original sites.