Discovery and properties of ultra-high redshift galaxies ($9<z<12$) in the JWST ERO SMACS 0723 Field

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We present a reduction and analysis of the \textit{James Webb Space Telescope} (JWST) SMACS~0723 field using new post-launch calibrations to conduct a search for ultra-high-redshift galaxies ($z > 9$) present within the Epoch of Reionisation.

• We conduct this search by modelling photometric redshifts in several ways for all sources and by applying conservative magnitude cuts ($m_{\rm F200W} < 28$) to identify strong Lyman breaks greater than 1 magnitude.
• We find four $z > 9$ candidate galaxies which have not previously been identified, with one object at $z = 11.5$, and another which is possibly a close pair of galaxies.
• We measure redshifts for candidate galaxies from other studies and find the recovery rate to be only 23 per cent, with many being assigned lower redshift, dusty solutions in our work.