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We study galaxies in JADES Deep to study the evolution of the ionising photonproduction efficiency, $\xi_{\rm{ion}}$, observed to increase with redshift. Weestimate $\xi_{\rm{ion}}$ for a sample of 677 galaxies at $z \sim 4 - 9$ usingNIRCam photometry. Specifically, combinations of the medium and wide bandsF335M-F356W and F410M-F444W to constrain emission lines that trace$\xi_{\rm{ion}}$: H$\alpha$ and [OIII]. Additionally, we use the spectralenergy distribution fitting code \texttt{Prospector} to fit all availablephotometry and infer galaxy properties. The flux measurements obtained viaphotometry are consistent with FRESCO and NIRSpec-derived fluxes. Moreover, theemission-line-inferred measurements are in tight agreement with the\texttt{Prospector} estimates. We also confirm the observed $\xi_{\rm{ion}}$trend with redshift and M$_{\rm{UV}}$, and find: $\log \xi_{\rm{ion}}(z,\text{M}_{\rm{UV}}) = (0.05 \pm 0.02)z + (0.11 \pm 0.02) \text{M}_{\rm{UV}}+ (27.33 \pm 0.37)$. We use \texttt{Prospector} to investigate correlations of$\xi_{\rm{ion}}$ with other galaxy properties. We see a clear correlationbetween $\xi_{\rm{ion}}$ and burstiness in the star formation history ofgalaxies, given by the ratio of recent to older star formation, whereburstiness is more prevalent at lower stellar masses. We also convolve our$\xi_{\rm{ion}}$ relations with luminosity functions from the literature, andconstant escape fractions of 10 and 20\%, to place constraints on the cosmicionising photon budget. By combining our results, we find that if our sample isrepresentative of the faint low-mass galaxy population, galaxies with burstystar formation are efficient enough in producing ionising photons and could beresponsible for the reionisation of the Universe.

Low-mass bursty galaxies in JADES efficiently produce ionising photons and could represent the main drivers of reionisation