Exploring the nature of UV-bright z ≳ 10 galaxies detected by JWST: star formation, black hole accretion, or a non-universal IMF?
arXiv (Cornell University)(2023)
摘要
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 ≤ z ≤ 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 ≳ 10. The model predicts a star formation history
dominated by UV faint (M_ UV > - 18) galaxies, with a Pop III
contribution of ≲ 10% (≲ 0.5%) at z ≃ 20 (z ≃
10). Stars are the primary sources of cosmic reionization, with 5 - 10 % of
ionizing photons escaping into the intergalatic medium at 5 ≤ z ≤ 10,
while the contribution of unobscured AGNs becomes dominant only at z ≲
5. The predicted stellar and AGN UV LFs reproduce the observational data at 5
≲ z ≲ 9 - 10. At higher redshift, CAT predicts a steeper
evolution in the faint-end slope (M_ UV > - 18), and a number density of
bright galaxies (M_ UV≃ -20) consistent with data at z ∼ 10 -
11, but smaller by 0.8 dex at z ∼ 12 - 13, and 1.2 dex at z ∼ 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
≲ 10 % of the total UV luminosity at M_ UV < - 19 and z
≳ 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 ∼ 12 - 13, and the disagreement at z
∼ 14 - 16 is reduced to 0.5 dex.
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关键词
black hole accretion,star formation,black hole,universal imf,jwst,uv-bright
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