Emergence and cosmic evolution of the Kennicutt–Schmidt relation driven by interstellar turbulence

¹ Observatoire Astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 67000 Strasbourg, France
e-mail: katarina.kraljic@astro.unistra.fr
² University of Strasbourg Institute for Advanced Study, 5 Allée du Général Rouvillois, 67083 Strasbourg, France
³ Lund Observatory, Division of Astrophysics, Department of Physics, Lund University, Box 43 221 00 Lund, Sweden
⁴ Institut d’Astrophysique de Paris, CNRS and Sorbonne Université, UMR 7095, 98 bis Boulevard Arago, 75014 Paris, France
⁵ IPhT, DRF-INP, UMR 3680, CEA, L’Orme des Merisiers, Bât 774, 91191 Gif-sur-Yvette, France
⁶ Korea Institute for Advanced Study, 85 Hoegi-ro, Dongdaemun-gu, Seoul 02455, Republic of Korea
⁷ Department of Astrophysics, American Museum of Natural History, 200 Central Park West, New York, NY 10024, USA
⁸ Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH, UK
⁹ Centre for Astrophysics Research, Department of Physics, Astronomy and Mathematics, University of Hertfordshire, Hatfield AL10 9AB, UK
¹⁰ Department of Astronomy and Yonsei University Observatory, Yonsei University, Seoul 03722, Republic of Korea
¹¹ Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Republic of Korea
¹² Steward Observatory, University of Arizona, 933 N. Cherry Ave, Tucson, AZ 85719, USA
¹³ School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD, UK
¹⁴ Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Bd de l’Observatoire, CS 34229, 06304 Nice Cedex 4, France

Received: 8 September 2023
Accepted: 16 November 2023

Abstract

The scaling relations between the gas content and star formation rate of galaxies provide useful insights into the processes governing their formation and evolution. We investigated the emergence and the physical drivers of the global Kennicutt–Schmidt (KS) relation at 0.25 ≤ z ≤ 4 in the cosmological hydrodynamic simulation NEWHORIZON, capturing the evolution of a few hundred galaxies with a resolution down to 34 pc. The details of this relation vary strongly with the stellar mass of galaxies and the redshift. A power-law relation Σ_SFR ∝ Σ_gas^a with a ≈ 1.4, like that found empirically, emerges at z ≈ 2 − 3 for the more massive half of the galaxy population. However, no such convergence is found in the lower-mass galaxies, for which the relation gets shallower with decreasing redshift. At galactic scales, the star formation activity correlates with the level of turbulence of the interstellar medium, quantified by the Mach number, rather than with the gas fraction (neutral or molecular), confirming the conclusions found in previous works. With decreasing redshift, the number of outliers with short depletion times diminishes, reducing the scatter of the KS relation, while the overall population of galaxies shifts toward low densities. Our results, from parsec-scale star formation models calibrated with local Universe physics, demonstrate that the cosmological evolution of the environmental (e.g., mergers) and internal conditions (e.g., gas fractions) conspire to shape the KS relation. This is an illustration of how the interplay of global and local processes leaves a detectable imprint on galactic-scale observables and scaling relations.