The ALPINE-CRISTAL-JWST survey: Spatially resolved star formation relations at z ∼ 5

October 2025 • 2025A&A...702A.206A

Authors • Accard, C. • Béthermin, M. • Boquien, M. • Buat, V. • Vallini, L. • Renaud, F. • Kraljic, K. • Aravena, M. • Cassata, P. • da Cunha, E. • Dam, P. • de Looze, I. • Dessauges-Zavadsky, M. • Dubois, Y. • Faisst, A. • Fudamoto, Y. • Ginolfi, M. • Gruppioni, C. • Han, S. • Herrera-Camus, R. • Inami, H. • Koekemoer, A. M. • Lemaux, B. C. • Li, J. • Li, Y. • Mobasher, B. • Molina, J. • Nanni, A. • Palla, M. • Pozzi, F. • Relaño, M. • Romano, M. • Sawant, P. • Spilker, J. • Tsujita, A. • Veraldi, E. • Villanueva, V. • Wang, W. • Yi, S. K. • Zamorani, G.

Abstract • Context. Star formation governs galaxy evolution, shaping stellar mass assembly and gas consumption across cosmic time. The Kennicutt-Schmidt (KS) relation, linking the star formation rate (SFR) and gas surface densities, is fundamental to understand star formation regulation, yet remains poorly constrained at z > 2 due to observational limitations and uncertainties in locally calibrated gas tracers. The [CII] 158 μm line has recently emerged as a key probe of the cold ISM and star formation in the early Universe. Aims. We investigate whether the resolved [CII]─SFR and KS relations established at low redshift remain valid at 4 < z < 6 by analysing 13 main-sequence galaxies from the ALPINE and CRISTAL surveys, using multi-wavelength data (HST, JWST, ALMA) at ∼2 kpc resolution. Methods. We performed pixel-by-pixel spectral energy distribution (SED) modelling with CIGALE on resolution-homogenised images. We developed a statistical framework to fit the [CII]─SFR relation that accounts for pixel covariance and compare our results to classical fitting methods. We tested two [CII]-to-gas conversion prescriptions to assess their impact on inferred gas surface densities and depletion times. Results. We find a resolved [CII]─SFR relation with a slope of 0.87 ± 0.15 and intrinsic scatter of 0.19 ± 0.03 dex, which is shallower and tighter than previous studies at z ∼ 5. The resolved KS relation is highly sensitive to the [CII]-to-gas conversion factor: using a fixed global α_[CII] yields depletion times of 0.5─1 Gyr, while a surface brightness-dependent W_[CII], accounting for local ISM conditions, places some galaxies with high gas density in the starburst regime (< 0.1 Gyr). Conclusions. Future inputs from both simulations and observations are required to better understand how the [CII]-to-gas conversion factor depends on local ISM properties. We need to break this fundamental limit to properly study the KS relation at z ≳ 4.

Links

• POSTSCRIPT https://www.aanda.org/10.1051/0004-6361/202556140/postscript
• PDF https://www.aanda.org/10.1051/0004-6361/202556140/pdf
• PREPRINT http://arxiv.org/abs/2508.13136
• DATA https://archive.stsci.edu/mastbibref.php?bibcode=2025A%26A...702A.206A
• ELECTR https://doi.org/10.1051%2F0004-6361%2F202556140