http://arxiv.org/abs/2305.04944
We use the Cosmic Archaeology Tool (CAT) semi-analytical model to explore the contribution of Population (Pop) III/II stars and active galactic nuclei (AGNs) to the galaxy UV luminosity function (LF) evolution at $4 \leq z \leq 20$. We compare in particular with recent JWST data in order to explore the apparent tension between observations and theoretical models in the number density of bright galaxies at $z \gtrsim 10$. The model predicts a star formation history dominated by UV faint ($M_{\rm UV} > – 18$) galaxies, with a Pop III contribution of $\lesssim 10\%$ ($\lesssim 0.5\%$) at $z \simeq 20$ ($z \simeq 10$). Stars are the primary sources of cosmic reionization, with $5 – 10 \%$ of ionizing photons escaping into the intergalatic medium at $5 \leq z \leq 10$, while the contribution of unobscured AGNs becomes dominant only at $z \lesssim 5$. The predicted stellar and AGN UV LFs reproduce the observational data at $5 \lesssim z \lesssim 9 – 10$. At higher redshift, CAT predicts a steeper evolution in the faint-end slope ($M_{\rm UV} > – 18$), and a number density of bright galaxies ($M_{\rm UV} \simeq -20$) consistent with data at $z \sim 10 – 11$, but smaller by 0.8 dex at $z \sim 12 – 13$, and 1.2 dex at $z \sim 14 – 16$, when compared to the values estimated by recent studies. Including the AGN emission does not affect the above findings, as AGNs contribute at most to $\lesssim 10 \%$ of the total UV luminosity at $M_{\rm UV} < – 19$ and $z \gtrsim 10$. Interestingly, considering a gradual transition in the stellar IMF, modulated by metallicity and redshift as suggested by recent simulations, the model agrees with JWST data at $z \sim 12 – 13$, and the disagreement at $z \sim 14 – 16$ is reduced to 0.5 dex.
A. Trinca, R. Schneider, R. Valiante, et. al.
Wed, 10 May 23
24/65
Comments: 18 pages, 9 figures. Submitted to MNRAS. Comments are welcome
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