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تسجيل مستخدم جديدStellar Properties of z ~ 8 Galaxies in the Reionization Lensing Cluster Survey
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Measurements of stellar properties of galaxies when the universe was less than one billion years old yield some of the only observational constraints of the onset of star formation. We present here the inclusion of textit{Spitzer}/IRAC imaging in the spectral energy distribution fitting of the seven highest-redshift galaxy candidates selected from the emph{Hubble Space Telescope} imaging of the Reionization Lensing Cluster Survey (RELICS). We find that for 6/8 textit{HST}-selected $zgtrsim8$ sources, the $zgtrsim8$ solutions are still strongly preferred over $zsim$1-2 solutions after the inclusion of textit{Spitzer} fluxes, and two prefer a $zsim 7$ solution, which we defer to a later analysis. We find a wide range of intrinsic stellar masses ($5times10^6 M_{odot}$ -- $4times10^9$ $M_{odot}$), star formation rates (0.2-14 $M_{odot}rm yr^{-1}$), and ages (30-600 Myr) among our sample. Of particular interest is Abell1763-1434, which shows evidence of an evolved stellar population at $zsim8$, implying its first generation of star formation occurred just $< 100$ Myr after the Big Bang. SPT0615-JD, a spatially resolved $zsim10$ candidate, remains at its high redshift, supported by deep textit{Spitzer}/IRAC data, and also shows some evidence for an evolved stellar population. Even with the lensed, bright apparent magnitudes of these $z gtrsim 8$ candidates (H = 26.1-27.8 AB mag), only the textit{James Webb Space Telescope} will be able further confirm the presence of evolved stellar populations early in the universe.
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