COSMOS2020: UV-selected galaxies at z ≥ 7.5

Creators: Kauffmann, O. B.; Ilbert, O.; Weaver, J. R.; McCracken, H. J.; Milvang-Jensen, B.; Brammer, G.; Davidzon, I.; Le Fèvre, O.; Liu, D.; Mobasher, B.; Moneti, A.; Shuntov, M.; Toft, S.; Casey, C. M.; Dunlop, J. S.; Kartaltepe, J. S.; Koekemoer, A. M.; Sanders, D. B.; Tresse, L.

Abstract

This paper presents a new search for z ≥ 7.5 galaxies using the COSMOS2020 photometric catalogues. Finding galaxies at the reionisation epoch through deep imaging surveys remains observationally challenging. The larger area covered by ground-based surveys such as COSMOS enables the discovery of the brightest galaxies at these high redshifts. Covering 1.4 deg^2, our COSMOS catalogues were constructed from the latest UltraVISTA data release (DR4) combined with the final Spitzer/IRAC COSMOS images and the Hyper-Suprime-Cam Subaru Strategic Program DR2 release. We identified 17 new 7.5 < z < 10 candidate sources, and confirm 15 previously published candidates. Using deblended photometry extracted by fitting surface brightness models on multi-band images, we selected four candidates which would be rejected using fixed aperture photometry. We tested the robustness of all our candidates by comparing six different photometric redshift estimates. Finally, we computed the galaxy UV luminosity function in three redshift bins centred at z = 8, 9, 10. We find no clear evolution of the number density of the brightest galaxies M_(UV) < −21.5, in agreement with previous works. Rapid changes in the quenching efficiency or attenuation by dust could explain such a lack of evolution between z ∼ 8 and z ∼ 9. A spectroscopic confirmation of the redshifts, already planned with JWST and the Keck telescopes, will be essential to confirm our results.

Additional Information

We are grateful to the referee for a careful reading of the manuscript and useful suggestions. This paper is dedicated to Olivier Le Fèvre who initiated this work and devoted so much energy and passion to building the COSMOS survey. We warmly acknowledge the contributions of the entire COSMOS collaboration consisting of more than 100 scientists. The HST-COSMOS program was supported through NASA grant HST-GO-09822. More information on the COSMOS survey is available at https://cosmos.astro.caltech.edu. This research is also partly supported by the Centre National d'Etudes Spatiales (CNES). OI acknowledges the funding of the French Agence Nationale de la Recherche for the project "SAGACE". HJMcC acknowledges support from the PNCG. ID has received funding from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No. 896225. This work used the CANDIDE computer system at the IAP supported by grants from the PNC, DIM-ACAV and the CNES and maintained by S. Rouberol. BMJ is supported in part by Independent Research Fund Denmark grant DFF – 7014-00017. The Cosmic Dawn Center (DAWN) is funded by the Danish National Research Foundation under grant No. 140. ST, GB and JW acknowledge support from the European Research Council (ERC) Consolidator Grant funding scheme (project ConTExt, grant No. 648179). CMC thanks the National Science Foundation for support through grants AST-1814034 and AST-2009577, and the Research Corporation for Science Advancement from a 2019 Cottrell Scholar Award sponsored by IF/THEN, an initiative of Lyda Hill Philanthropies. CMC thanks the National Science Foundation for support through grants AST-1814034 and AST-2009577, and the Research Corporation for Science Advancement from a 2019 Cottrell Scholar Award sponsored by IF/THEN, an initiative of Lyda Hill Philanthropies. The authors wish to recognise and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This work is based on data products from observations made with ESO Telescopes at the La Silla Paranal Observatory under ESO program ID 179.A-2005 and on data products produced by CALET and the Cambridge Astronomy Survey Unit on behalf of the UltraVISTA consortium. This work is based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

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Resource type: Journal Article
Publisher: EDP Sciences
Published in: Astronomy and Astrophysics, 667, Art. No. A65, ISSN: 0004-6361.