The extreme starburst J1044+0353 blows kiloparsec-scale bubbles

Abstract We report the discovery of a kiloparsec-scale lacy filamentary structure in low-surface-brightness H$\alpha$ and [O iii]$\lambda 5007$ emission around the low-redshift, extremely metal-poor and compact reionization-era analogue SDSS J1044+0353. We identify seven elliptical arcs in H$\alpha$ emission at $\mathrm{SB}_\mathrm{H\alpha }$ $\sim$ 1–2 $\times$$10^{-18}$ erg s$^{-1}$ cm$^{-2}$ arcsec$^{-2}$. We interpret these features as limb-brightened giant shells that bound egg-shaped super-bubbles with 3–3.5 kpc radii. These shells are significantly larger than the known giant shells around nearby star-forming dwarfs. Kinematic maps reveal a gradient perpendicular to the major axis and line broadening in the outskirts. The latter, when interpreted due to line splitting of the expanding shells, suggests expansion velocities of $\sim$40 km s$^{-1}$. Notably, the properties of the giant shells evade description by simple analytic prescriptions for energy- and momentum-driven super-bubbles.