Abstract

When the first galaxies formed and starlight escaped into the intergalactic medium to reionize it, galaxy formation and reionization were both highly inhomogeneous in time and space, and fully coupled by mutual feedback. To show how this imprinted the UV luminosity function (UVLF) of reionization-era galaxies, we use our large-scale, radiation-hydrodynamics simulation CoDa II to derive the time- and space-varying halo mass function and UVLF, from z ≃ 6–15. That UVLF correlates strongly with local reionization redshift: earlier-reionizing regions have UVLFs that are higher, more extended to brighter magnitudes, and flatter at the faint end than later-reionizing regions observed at the same z. In general, as a region reionizes, the faint-end slope of its local UVLF flattens, and, by z = 6 (when reionization ended), the global UVLF, too, exhibits a flattened faint-end slope, ‘rolling-over’ at M_UV ≳ -17. CoDa II’s UVLF is broadly consistent with cluster-lensed galaxy observations of the Hubble Frontier Fields at z = 6–8, including the faint end, except for the faintest data point at z = 6, based on one galaxy at M_UV = -12.5. According to CoDa II, the probability of observing the latter is $$\sim 5~{{\ \rm per\ cent}}$$. However, the effective volume searched at this magnitude is very small, and is thus subject to significant cosmic variance. Here, we find that previous methods adopted to calculate the uncertainty due to cosmic variance underestimated it on such small scales by a factor of 2–4, primarily by underestimating the variance in halo abundance when the sample volume is small.

Authors:

Dawoodbhoy, Taha  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-4760-7016"

Shapiro, Paul R. ^[1]; Ocvirk, Pierre  ^[2];

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• Search DOE PAGES for ORCID "0000-0002-8488-504X"

Lewis, Joseph W.  ^[3];

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Aubert, Dominique ^[2]; Sorce, Jenny G.  ^[4];

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Ahn, Kyungjin ^[5]; Iliev, Ilian T.  ^[6];

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Park, Hyunbae ^[7]; Teyssier, Romain  ^[8];

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• Search DOE PAGES for ORCID "0000-0001-7689-0933"

Yepes, Gustavo  ^[9]

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• Search DOE PAGES for ORCID "0000-0001-5031-7936"

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+ Show Author Affiliations

1. Univ. of Texas, Austin, TX (United States)
2. Université de Strasbourg (France)
3. University of Heidelberg (Germany). Center for Astronomy; Max-Planck-Institut für Astronomie, Heidelberg (Germany)
4. Univ. Lille (France); Centre National de la Recherche Scientifique (CNRS) (France); Leibniz Institute for Astrophysics Potsdam (AIP), Potsdam (Germany); Univ. Paris-Saclay, Orsay (France)
5. Chosun University, Gwangju (Korea, Republic of)
6. Univ. of Sussex, Brighton (United Kingdom)
7. Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); Univ. of Tokyo, Kashiwa (Japan)
8. Princeton Univ., NJ (United States)
9. Univ. Autonoma de Madrid (Spain)

Publication Date:

Wed Aug 02 00:00:00 EDT 2023

Research Org.:

Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF)

Sponsoring Org.:

USDOE Office of Science (SC), High Energy Physics (HEP); National Science Foundation (NSF); National Aeronautics and Space Administration (NASA)

OSTI Identifier:

2305391

Grant/Contract Number:  

AC02-05CH11231; AC05-00OR22725; DGE-1610403; 80NSSC22K175

Resource Type:

Accepted Manuscript

Journal Name:

Monthly Notices of the Royal Astronomical Society

Additional Journal Information:

Journal Volume: 524; Journal Issue: 4; Journal ID: ISSN 0035-8711

Publisher:

Oxford University Press

Country of Publication:

United States

Language:

English

Subject:

79 ASTRONOMY AND ASTROPHYSICS; galaxies: high-redshift; galaxies: luminosity function; mass function; dark ages; reionization; first stars; cosmology: theory