Abstract
Context. According to the current paradigm of galaxy formation, the first galaxies likely formed within large dark matter haloes. The fragmentation of these massive haloes led to the formation of galaxy protoclusters, which are usually composed of one to a few bright objects, surrounded by numerous fainter (and less massive) galaxies. These early structures could have played a major role in reionising the neutral hydrogen within the first billion years of the Universe, especially if their number density is significant.
Aims. Taking advantage of the unprecedented sensitivity reached by the James Webb Space Telescope (JWST), galaxy protoclusters can now be identified and studied in increasing numbers beyond z ≥ 6. Characterising their contribution to the UV photon budget could supply new insights into the reionisation process.
Methods. We analysed the first JWST dataset behind SMACS0723−7327 to search for protoclusters at z ≥ 6, combining the available spectroscopic and photometric data. We then compared our findings with semi-analytical models and simulations.
Results. In addition to two bright galaxies (≤26.5 AB in F277W), separated by ∼11″and spectroscopically confirmed at zspec = 7.66, we identify six additional galaxies with similar colours within a θ ∼ 20″ radius (corresponding to R ∼ 60 − 90 kpc in the source plane). Using several methods, we estimate the mass of the dark matter halo of this protocluster as ∼3.3 × 1011 M⊙, accounting for magnification, consistent with various predictions. The physical properties of all protocluster members are also in excellent agreement with what has been previously found at lower redshifts: star formation main sequence and protocluster size. This detection adds to just a few protoclusters currently known in the first billion years of the universe. These z ≥ 7 galaxy protoclusters may play an important role in cosmic reionisation.
Subject
Space and Planetary Science,Astronomy and Astrophysics
Reference62 articles.
1. Protocluster detection in simulations of HSC–SSP and the 10-yr LSST forecast, using PCcones
2. Atek H., Shuntov M., Furtak L.J., et al. 2022, MNRAS, submitted [arXiv:2207.12338]
3. THE AVERAGE STAR FORMATION HISTORIES OF GALAXIES IN DARK MATTER HALOS FROMz= 0-8
4. Bouwens R. J., Illingworth G. D., Ellis R. S., Oesch P. A., & Stefanon M. 2022, A&AS, submitted [arXiv:2205.11526]
5. The First Galaxies
Cited by
22 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献