dorsal/arxiv
View SchemaRelatively Fast and Reasonably Furious: Evidence for Increased Burstiness in Smaller Halos at Cosmic Dawn
| Authors | Julian B. Muñoz, John Chisholm, Guochao Sun, Jenna Samuel, Jordan Mirocha, Emily Bregou, Alessandra Venditti, Mahdi Qezlou, Charlotte Simmonds, Ryan Endsley |
|---|---|
| Categories | |
| ArXiv ID | 2601.07912vv1 |
| URL | https://arxiv.org/abs/2601.07912 |
| License | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ |
Abstract
We introduce an effective framework to model star-formation burstiness and use it to jointly fit galaxy UV luminosity functions (UVLFs), clustering, and H$\alpha$/UV ratios, providing the first robust empirical evidence that early galaxies hosted in lower-mass halos are burstier. Using $z\sim 4-6$ observations, we find that galaxies show approximately $0.6$ dex of SFR variability if hosted in halos of $M_h = 10^{11}\, M_\odot$ (typical of $M_{\rm UV}\approx -19$ galaxies at $z = 6$). This translates into a scatter of $\sigma_{M_{\rm UV}}\approx 0.75$ in the UVLF, in line with past findings. Strikingly, we find that burstiness grows for galaxies hosted in smaller halos, reaching $\gtrsim 1$ dex for $M_h \leq 10^{9}\, M_\odot$ (corresponding to $\sigma_{M_{\rm UV}} \approx 1.5$ for faint $M_{\rm UV} \gtrsim -15$ galaxies). Extrapolating to higher redshifts, when small halos were more prevalent, the inferred mass-dependent burstiness can reproduce observed UVLFs up to $z\sim 17$ within 1$\sigma$, potentially alleviating the tension between pre- and post-JWST galaxy-formation models. Current observations allow us to constrain burst timescales to approximately $20$ Myr, consistent with expectations from supernova feedback, and suggest broad distributions of ionizing efficiencies at fixed $M_{\rm UV}$. Our results demonstrate that mass-dependent burstiness, as predicted by hydrodynamical simulations, is critical for understanding the mass assembly of early galaxies.
{
"annotation_id": "a597201d-e8bd-4135-932b-feeb67675605",
"date_created": "2026-02-17T05:53:12.333000Z",
"date_modified": "2026-02-17T05:53:12.333000Z",
"file_hash": "526d4a5d9389b177800fe49c29c80abf4d6da6fde11333a39f1aea3dbe295102",
"private": false,
"record": {
"abstract": "We introduce an effective framework to model star-formation burstiness and use it to jointly fit galaxy UV luminosity functions (UVLFs), clustering, and H$\\alpha$/UV ratios, providing the first robust empirical evidence that early galaxies hosted in lower-mass halos are burstier. Using $z\\sim 4-6$ observations, we find that galaxies show approximately $0.6$ dex of SFR variability if hosted in halos of $M_h = 10^{11}\\, M_\\odot$ (typical of $M_{\\rm UV}\\approx -19$ galaxies at $z = 6$). This translates into a scatter of $\\sigma_{M_{\\rm UV}}\\approx 0.75$ in the UVLF, in line with past findings. Strikingly, we find that burstiness grows for galaxies hosted in smaller halos, reaching $\\gtrsim 1$ dex for $M_h \\leq 10^{9}\\, M_\\odot$ (corresponding to $\\sigma_{M_{\\rm UV}} \\approx 1.5$ for faint $M_{\\rm UV} \\gtrsim -15$ galaxies). Extrapolating to higher redshifts, when small halos were more prevalent, the inferred mass-dependent burstiness can reproduce observed UVLFs up to $z\\sim 17$ within 1$\\sigma$, potentially alleviating the tension between pre- and post-JWST galaxy-formation models. Current observations allow us to constrain burst timescales to approximately $20$ Myr, consistent with expectations from supernova feedback, and suggest broad distributions of ionizing efficiencies at fixed $M_{\\rm UV}$. Our results demonstrate that mass-dependent burstiness, as predicted by hydrodynamical simulations, is critical for understanding the mass assembly of early galaxies.",
"arxiv_id": "2601.07912",
"authors": [
"Julian B. Mu\u00f1oz",
"John Chisholm",
"Guochao Sun",
"Jenna Samuel",
"Jordan Mirocha",
"Emily Bregou",
"Alessandra Venditti",
"Mahdi Qezlou",
"Charlotte Simmonds",
"Ryan Endsley"
],
"categories": [
"astro-ph.GA",
"astro-ph.CO"
],
"license": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
"title": "Relatively Fast and Reasonably Furious: Evidence for Increased Burstiness in Smaller Halos at Cosmic Dawn",
"url": "https://arxiv.org/abs/2601.07912",
"version": "v1"
},
"schema_id": "dorsal/arxiv",
"source": {
"execution_id": "6990e24a-7457-40ee-a05c-81e6a70e4cd5",
"id": "arXiv Dataset",
"type": "Model",
"variant": "snapshot-2026-01-17",
"version": "0.1.0"
},
"user_id": 1000002
}