The ionizing photon production efficiency of bright <i>z</i> ∼ 2 − 5 galaxies

We investigate the production efficiency of ionizing photons ($\xi_{ion}^*$) 1174 galaxies with secure redshift at z=2-5 from VANDELS survey to determine relation between emission and physical properties bright massive sources. constrain $\xi_{ion}^*$ galaxy parameters by means spectro-photometric fits performed BEAGLE code. The analysis exploits multi-band photometry in fields, measurement UV rest-frame lines (CIII]$\lambda 1909$, HeII$\lambda 1640$, OIII]$\lambda 1666$) deep VIMOS spectra. find no clear evolution within probed range. slightly increases fainter $M_{UV}$, bluer slopes, but these trends are less evident when restricting a complete subsample log(M$_{star}$/M$_{\odot}$)$>$9.5. significant trend increasing EW(Ly$\alpha$), an average log($\xi_{ion}^*$/Hz erg$^{-1}$)$>$25 EW$>$50\AA, higher for high-EW CIII]$\lambda 1909$ 1666$ emitters. most correlations found respect stellar mass, specific star-formation rate (sSFR) SFR surface density ($\Sigma_{SFR}$). sSFR shows monotonic increase erg$^{-1}$) $\sim$24.5 log(sSFR)$\sim$-9.5$yr^{-1}$ $\sim$25.5 log(sSFR)$\sim$-7.5$yr^{-1}$, low scatter little dependence on mass. objects above main-sequence consistently have higher-than-average $\xi_{ion}^*$. A $\Sigma_{SFR}$ is also found, $\Sigma_{SFR}>$10 M$_{\odot}/yr/kpc^2$.(Abridged)