The slope and scatter of the star forming main sequence at z~5 : reconciling observations with simulations
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2025
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| author | Di Cesare, Claudia Matthee, Jorryt Naidu, Rohan P. Torralba, Alberto Kotiwale, Gauri Kramarenko, Ivan G. Blaizot, Jeremy Rosdahl, Joakim Leja, Joel Iani, Edoardo Adamo, Angela Covelo-Paz, Alba Furtak, Lukas J. Heintz, Kasper E. Mascia, Sara Navarrete, Benjamín Oesch, Pascal A. Romano, Michael Shivaei, Irene Tacchella, Sandro |
| author_facet | Di Cesare, Claudia Matthee, Jorryt Naidu, Rohan P. Torralba, Alberto Kotiwale, Gauri Kramarenko, Ivan G. Blaizot, Jeremy Rosdahl, Joakim Leja, Joel Iani, Edoardo Adamo, Angela Covelo-Paz, Alba Furtak, Lukas J. Heintz, Kasper E. Mascia, Sara Navarrete, Benjamín Oesch, Pascal A. Romano, Michael Shivaei, Irene Tacchella, Sandro |
| contents | Galaxies exhibit a tight correlation between their star-formation rate and stellar mass over a wide redshift range known as the star-forming main sequence (SFMS). With JWST, we can now investigate the SFMS at high redshifts down to masses of $\sim10^6$ M$_{\odot}$, using sensitive star-formation rate tracers such as H$α$ emission -- which allow us to probe the variability in star formation histories. We present inferences of the SFMS based on 316 H$α$-selected galaxies at $z\sim4$-$5$ with $\log(\rm M_\star/M_\odot) = 6.4$ -$10.6$. These galaxies were identified behind the Abell 2744 lensing cluster with NIRCam grism spectroscopy from the ``All the Little Things'' (ALT) survey. At face value, our data suggest a shallow slope of the SFMS (SFR $\propto \mathrm{M}_\star^α$, with $α=0.45$). After correcting for the H$α$-flux limited nature of our survey using a Bayesian framework, the slope steepens to $α= 0.59^{+0.10}_{-0.09}$, whereas current data on their own are inconclusive on the mass dependence of the scatter. These slopes differ significantly from the slope of $\approx1$ expected from the observed evolution of the galaxy stellar mass function and from simulations. When fixing the slope to $α=1$, we find evidence for a decreasing intrinsic scatter with stellar mass (from $\approx 0.5$ dex at M$_\star=10^8$ M$_\odot$ to $0.4$ dex at M$_\star=10^{10}$ M$_\odot$). This tension might be explained by a (combination of) luminosity-dependent SFR(H$α$) calibration, a population of (mini)-quenched low-mass galaxies, or underestimated dust attenuation in high-mass galaxies. Future deep observations across facilities can quantify these processes, enabling better insights into the variability of star formation histories. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2510_19044 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | The slope and scatter of the star forming main sequence at z~5 : reconciling observations with simulations Di Cesare, Claudia Matthee, Jorryt Naidu, Rohan P. Torralba, Alberto Kotiwale, Gauri Kramarenko, Ivan G. Blaizot, Jeremy Rosdahl, Joakim Leja, Joel Iani, Edoardo Adamo, Angela Covelo-Paz, Alba Furtak, Lukas J. Heintz, Kasper E. Mascia, Sara Navarrete, Benjamín Oesch, Pascal A. Romano, Michael Shivaei, Irene Tacchella, Sandro Astrophysics of Galaxies Galaxies exhibit a tight correlation between their star-formation rate and stellar mass over a wide redshift range known as the star-forming main sequence (SFMS). With JWST, we can now investigate the SFMS at high redshifts down to masses of $\sim10^6$ M$_{\odot}$, using sensitive star-formation rate tracers such as H$α$ emission -- which allow us to probe the variability in star formation histories. We present inferences of the SFMS based on 316 H$α$-selected galaxies at $z\sim4$-$5$ with $\log(\rm M_\star/M_\odot) = 6.4$ -$10.6$. These galaxies were identified behind the Abell 2744 lensing cluster with NIRCam grism spectroscopy from the ``All the Little Things'' (ALT) survey. At face value, our data suggest a shallow slope of the SFMS (SFR $\propto \mathrm{M}_\star^α$, with $α=0.45$). After correcting for the H$α$-flux limited nature of our survey using a Bayesian framework, the slope steepens to $α= 0.59^{+0.10}_{-0.09}$, whereas current data on their own are inconclusive on the mass dependence of the scatter. These slopes differ significantly from the slope of $\approx1$ expected from the observed evolution of the galaxy stellar mass function and from simulations. When fixing the slope to $α=1$, we find evidence for a decreasing intrinsic scatter with stellar mass (from $\approx 0.5$ dex at M$_\star=10^8$ M$_\odot$ to $0.4$ dex at M$_\star=10^{10}$ M$_\odot$). This tension might be explained by a (combination of) luminosity-dependent SFR(H$α$) calibration, a population of (mini)-quenched low-mass galaxies, or underestimated dust attenuation in high-mass galaxies. Future deep observations across facilities can quantify these processes, enabling better insights into the variability of star formation histories. |
| title | The slope and scatter of the star forming main sequence at z~5 : reconciling observations with simulations |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2510.19044 |