Dual Signatures of Bursty Star Formation in High-Redshift UV Luminosity Functions
Abstract
The UV luminosity function (UVLF) encodes key information about galaxy formation. The slowly evolving bright-end UVLFs at z≳10 have made UV variability from bursty star formation a promising explanation, but the impact of such variability need not be restricted to the bright end. Motivated by ultra-deep measurements of the z≃7 UVLF, we investigate whether UV variability can provide a unified interpretation of the low-mass star formation efficiency (SFE) at z≃7 and the abundance of UV-bright galaxies at z≳12. Using abundance matching, we show that a steep faint-end UVLF at z≃7 admits a range of interpretations. For modest, mass-independent UV variability, the inferred median SFE starts flattening below Mh ∼1010.5 M⊙. If UV variability instead grows with decreasing halo mass---a possibility motivated by simulations and observations---the inferred median SFE is steeper and lower by a factor of about three at ∼109 M⊙, consistent with stronger feedback suppression in low-mass halos. Calibrated to the common target z≃7 UVLF, these two scenarios diverge strongly when extrapolated to 12≲ z≲17 under redshift-independent UV variability and SFE prescriptions. Strongly mass-dependent MUV scatter links the steep z≃7 faint-end slope and high z≳12 bright-end abundance as dual signatures of burstiness in similarly low-mass halos. Stronger variability makes bright galaxies contribute a larger fraction of the UV luminosity density, whereas weaker variability favors faint sources, despite their similar predicted reionization histories. At fixed MUV, UV variability broadens the halo mass distribution and lowers the clustering bias, which provides a useful diagnostic of burstiness for JWST and Roman.
Related
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- The THESAN-ZOOM project: the delayed rise of Lyman continuum escape fractions in bursty high-redshift galaxies
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- The Pandora project. II: how non-thermal physics drives bursty star formation and temperate mass-loaded outflows in dwarf galaxies
- HI Emission Recovery in the Low-Redshift Radio Population: Host-Galaxy and Radio-Luminosity Dependence in FASHI and LoTSS
BibTeX
@misc{sun2026dual,
title = {{Dual Signatures of Bursty Star Formation in High-Redshift UV Luminosity Functions}},
author = {Guochao Sun and Claude-André Faucher-Giguère and Steven R. Furlanetto and Adam Lidz},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.22431},
eprint = {2609.22431},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.22431},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Dual Signatures of Bursty Star Formation in High-Redshift UV Luminosity Functions
AU - Guochao Sun
AU - Claude-André Faucher-Giguère
AU - Steven R. Furlanetto
AU - Adam Lidz
PY - 2026
DA - 2026/09/18
PB - arXiv
DO - 10.48550/arxiv.2609.22431
UR - https://arxiv.org/abs/2609.22431
AB - The UV luminosity function (UVLF) encodes key information about galaxy formation. The slowly evolving bright-end UVLFs at z≳10 have made UV variability from bursty star formation a promising explanation, but the impact of such variability need not be restricted to the bright end. Motivated by ultra-deep measurements of the z≃7 UVLF, we investigate whether UV variability can provide a unified interpretation of the low-mass star formation efficiency (SFE) at z≃7 and the abundance of UV-bright galaxies at z≳12. Using abundance matching, we show that a steep faint-end UVLF at z≃7 admits a range of interpretations. For modest, mass-independent UV variability, the inferred median SFE starts flattening below M_h ∼10^10.5 M_⊙. If UV variability instead grows with decreasing halo mass---a possibility motivated by simulations and observations---the inferred median SFE is steeper and lower by a factor of about three at ∼10^9 M_⊙, consistent with stronger feedback suppression in low-mass halos. Calibrated to the common target z≃7 UVLF, these two scenarios diverge strongly when extrapolated to 12≲ z≲17 under redshift-independent UV variability and SFE prescriptions. Strongly mass-dependent M_UV scatter links the steep z≃7 faint-end slope and high z≳12 bright-end abundance as dual signatures of burstiness in similarly low-mass halos. Stronger variability makes bright galaxies contribute a larger fraction of the UV luminosity density, whereas weaker variability favors faint sources, despite their similar predicted reionization histories. At fixed M_UV, UV variability broadens the halo mass distribution and lowers the clustering bias, which provides a useful diagnostic of burstiness for JWST and Roman.
ER -