Probing the Star Formation Main Sequence down to 10$^{7} M_\odot$ at $1 < z < 9$
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| Format: | Preprint |
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2025
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| author | Mérida, Rosa M. Sawicki, Marcin Iyer, Kartheik G. Noirot, Gaël Willott, Chris J. Bradač, Maruša Desprez, Guillaume Martis, Nicholas S. Muzzin, Adam Rihtaršič, Gregor Sarrouh, Ghassan T. E. Favaro, Jeremy Gaspar, Gaia Harshan, Anishya Judež, Jon |
| author_facet | Mérida, Rosa M. Sawicki, Marcin Iyer, Kartheik G. Noirot, Gaël Willott, Chris J. Bradač, Maruša Desprez, Guillaume Martis, Nicholas S. Muzzin, Adam Rihtaršič, Gregor Sarrouh, Ghassan T. E. Favaro, Jeremy Gaspar, Gaia Harshan, Anishya Judež, Jon |
| contents | The Main Sequence of Star-Forming Galaxies (SFGMS or MS) is a fundamental scaling relation that provides a global framework for studying galaxy formation and evolution, as well as insight into the complex star formation histories (SFHs) of individual galaxies. In this work, we combine large-area pre-JWST surveys (COSMOS2020, CANDELS), which probe high-$M_\star$ sources (${>10^9\,M_\odot}$), with SHARDS/CANDELS FAINT and JWST data from CANUCS, CEERS, JADES, and UNCOVER, to obtain a high-$z$, star formation rate (SFR) and stellar mass ($M_\star$) complete sample spanning both high- and low-$M_\star$ regimes. Completeness in both $M_\star$ and SFR is key to avoiding biases introduced by low-mass, highly star-forming objects. Our combined data set is 80% complete down to $10^{7.6}\,M_\odot$ at $z\sim1$ ($10^{8.8}\,M_\odot$ at $z\sim9$). The overall intrinsic MS slope (based on the SFR$_{100}$ and $M_\star$ derived with Dense Basis and nonparametric SFHs) shows little evolution up to $z\sim5$, with values $\sim0.7 - 0.8$. The slope in the low-$M_\star$ regime becomes steeper than that in the high-$M_\star$ end at least up to $z\sim5$, but the strength of this change is highly dependent on the assumptions made on the symmetry of the uncertainties in $M_\star$ and SFR. If real, the steepening suggests reduced star formation efficiency or declining gas content with decreasing $M_\star$. The transition between the low-$M_\star$ regime and the canonical MS occurs around $10^{9.5}\,M_\odot$, independent of $z$. This critical value may coincide with the assembly of galaxies' disks, which can provide a mechanism for self-regulation that stabilizes them against feedback. The intrinsic scatter is compatible with canonical estimates, also at low-$M_\star$, ranging from $0.2-0.3$ dex. This is indicative of rapid variations in star formation being averaged out over $\lesssim100$ Myr. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2509_22871 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Probing the Star Formation Main Sequence down to 10$^{7} M_\odot$ at $1 < z < 9$ Mérida, Rosa M. Sawicki, Marcin Iyer, Kartheik G. Noirot, Gaël Willott, Chris J. Bradač, Maruša Desprez, Guillaume Martis, Nicholas S. Muzzin, Adam Rihtaršič, Gregor Sarrouh, Ghassan T. E. Favaro, Jeremy Gaspar, Gaia Harshan, Anishya Judež, Jon Astrophysics of Galaxies The Main Sequence of Star-Forming Galaxies (SFGMS or MS) is a fundamental scaling relation that provides a global framework for studying galaxy formation and evolution, as well as insight into the complex star formation histories (SFHs) of individual galaxies. In this work, we combine large-area pre-JWST surveys (COSMOS2020, CANDELS), which probe high-$M_\star$ sources (${>10^9\,M_\odot}$), with SHARDS/CANDELS FAINT and JWST data from CANUCS, CEERS, JADES, and UNCOVER, to obtain a high-$z$, star formation rate (SFR) and stellar mass ($M_\star$) complete sample spanning both high- and low-$M_\star$ regimes. Completeness in both $M_\star$ and SFR is key to avoiding biases introduced by low-mass, highly star-forming objects. Our combined data set is 80% complete down to $10^{7.6}\,M_\odot$ at $z\sim1$ ($10^{8.8}\,M_\odot$ at $z\sim9$). The overall intrinsic MS slope (based on the SFR$_{100}$ and $M_\star$ derived with Dense Basis and nonparametric SFHs) shows little evolution up to $z\sim5$, with values $\sim0.7 - 0.8$. The slope in the low-$M_\star$ regime becomes steeper than that in the high-$M_\star$ end at least up to $z\sim5$, but the strength of this change is highly dependent on the assumptions made on the symmetry of the uncertainties in $M_\star$ and SFR. If real, the steepening suggests reduced star formation efficiency or declining gas content with decreasing $M_\star$. The transition between the low-$M_\star$ regime and the canonical MS occurs around $10^{9.5}\,M_\odot$, independent of $z$. This critical value may coincide with the assembly of galaxies' disks, which can provide a mechanism for self-regulation that stabilizes them against feedback. The intrinsic scatter is compatible with canonical estimates, also at low-$M_\star$, ranging from $0.2-0.3$ dex. This is indicative of rapid variations in star formation being averaged out over $\lesssim100$ Myr. |
| title | Probing the Star Formation Main Sequence down to 10$^{7} M_\odot$ at $1 < z < 9$ |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2509.22871 |