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We discuss the spectral energy distributions and physical properties of sixgalaxies whose photometric redshifts suggest they lie beyond a redshift$z\simeq$9. Each was selected on account of a prominent excess seen in theSpitzer/IRAC 4.5$\mu$m band which, for a redshift above $z=9.0$, likelyindicates the presence of a rest-frame Balmer break and a stellar componentthat formed earlier than a redshift $z\simeq10$. In addition to constrainingthe earlier star formation activity on the basis of fits using stellarpopulation models with BAGPIPES, we have undertaken the necessary, butchallenging, follow-up spectroscopy for each candidate using variouscombinations of Keck/MOSFIRE, VLT/X-shooter, Gemini/FLAMINGOS2 and ALMA. Basedon either Lyman-$\alpha$ or [OIII] 88 $\mu$m emission, we determine aconvincing redshift of $z$=8.78 for GN-z-10-3 and a likely redshift of $z$=9.28for the lensed galaxy MACS0416-JD. For GN-z9-1, we conclude the case remainspromising for a source beyond $z\simeq$9. Together with earlier spectroscopicdata for MACS1149-JD1, our analysis of this enlarged sample provides furthersupport for a cosmic star formation history extending beyond redshifts$z\simeq$10. We use our best-fit stellar population models to reconstruct thepast rest-frame UV luminosities of our sources and discuss the implications fortracing earlier progenitors of such systems with the James Webb SpaceTelescope.

Probing Cosmic Dawn : Ages and Star Formation Histories of Candidate $z\geq$9 Galaxies