Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 2609.40233

Sub-kiloparsec Test of the Kennicutt-Schmidt Relation in a Strongly Lensed Dusty Star-Forming Galaxy at z~2.78

C. Cornil-Baïotto·J. Molina·G. Mahler·G. Rihtaršič·M. Boquien·M. Bradač·E. Ibar·A. H. Gonzalez·T. Verdugo·O. López-Cruz·J. Magaña·V. Motta
View original source ↗Read source document ↗Export metadata ↓

Abstract

[abridged] Star formation is a key process driving galaxy evolution, but understanding how it proceeds within the interstellar medium (ISM) requires resolving cold molecular gas and dust on sub-kpc scales. At z~2-3, near the peak of cosmic star formation, such resolution can generally only be achieved through strong gravitational lensing. We present an ALMA study of SMMJ0658, a 20x-magnified main-sequence star-forming galaxy at z=2.7768 +/- 0.0002, lensed by the Bullet Cluster (z=0.296) into three images. We use 0.2" and 0.6" ALMA Band-3 observations to test the Kennicutt-Schmidt (KS) relation at sub-kpc scales at cosmic noon. Using a JWST-based strong-lensing model of the Bullet Cluster, we reconstruct source-plane CO(3-2) and rest-frame 803um dust-continuum maps down to ~200pc scales. We derive spatially resolved molecular gas and star formation rate surface densities, depletion times, and the scale dependence of the CO-to-dust flux ratio over 200pc-3.2kpc apertures. The 0.2" ALMA data reveal massive, dense star-forming clumps, with Sigma_mol ~1.3-2.3 x 10^3 M_sun pc^-2, Sigma_SFR ~0.5-2.3 M_sun yr^-1 kpc^-2, and tau_dep ~0.82-2.56 Gyr. CO-dust spatial decorrelation produces a strong scale dependence in tau_dep. We find a KS-relation breakdown scale of 0.8 +/- 0.1 kpc, consistent with individual regions tracing distinct stages of the star-formation cycle. The ALMA and JWST data also reveal evidence for a lensed galaxy pair at z~2.78, although whether SMMJ0658 is undergoing an early-stage interaction remains uncertain. Our results show that the apparent universality of the KS relation breaks down once individual star-forming regions are spatially resolved, in line with observations from the local universe to z~1. We extend this picture to z~2.78, providing new insight into the resolved properties of the clumpy cold ISM and the star-formation cycle at cosmic noon.

Explore related subjects

astro-ph.GA

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

C. Cornil-Baïotto, J. Molina, G. Mahler, G. Rihtaršič, M. Boquien, M. Bradač, E. Ibar, A. H. Gonzalez, T. Verdugo, O. López-Cruz, J. Magaña, V. Motta. 2026-09-30. Sub-kiloparsec Test of the Kennicutt-Schmidt Relation in a Strongly Lensed Dusty Star-Forming Galaxy at z~2.78. https://arxiv.org/abs/2609.40233

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Spatio-Temporal Log-Gaussian Cox-Hawkes Processes with Inhibition and Excitation for Stochastic Star Formation

We establish a connection between the stochastic self-propagating star-formation (SSPSF) model and spatio-temporal point processes by showing that the SSPSF update law admits a conditional Poisson representation. Building on this connection, we propose a spatio-temporal log-Gaussian Cox-Hawkes process as a continuous point process model for stochastic star formation. The model represents star-formation events as point patterns driven jointly by deterministic galactic structure, latent spatio-temporal background variation, and dependence on past events. Its key feature is that the deterministic mean field, latent Gaussian random field, and history-dependent interaction field enter through a single log-intensity. This log-scale construction differs from additive Cox-Hawkes formulations and allows the history effect to be signed, past events may either increase or decrease future local intensity while the conditional intensity remains positive. The resulting framework provides an interpretable point-process model for representing latent clustering, self-excitation, local inhibition, and event-driven propagation in stochastic star formation. Further extensions replace the constant history coefficient with deterministic or random fields representing source influence, local response or both. Beyond linking SSPSF to spatio-temporal point-process theory, it offers a continuous stochastic formulation for analysing the propagation of star formation in galaxies and for interpreting observational surveys of star-forming regions within a unified statistical model.

astro-ph.GA↗
arXiv2026

The Einstein Gap: an unrecognised strong lensing feature in weak lensing mass density profiles

Magnification bias cross-correlations between galaxy clusters and high-redshift submillimetre galaxies have recently revealed a characteristic signal deficit at intermediate angular scales, termed the Einstein Gap, that appears consistently across all lens types and cannot be explained by any single theoretical mass density profile. In this work we identify for the first time the most plausible physical origin of this feature through a combination of observational tests and improved lensing simulations. Using galaxy clusters to characterise the satellite population and as the lens sample, we show that the gap is detected at high statistical significance, accounting for the full covariance of the stacked profile. Then, we demonstrate that the Einstein Gap is robust across three independent estimators of the angular cross-correlation function, strengthens as the positional smoothing is reduced, and scales systematically with the bright central galaxy stellar mass. Finally, we show that the projected radial distribution of satellite galaxies is smooth and continuous at all angular scales with no depression corresponding to the gap, disfavouring both a statistical artifact and a genuine absence of mass as its origin. An improved magnification bias simulator incorporating full ray-tracing via the lens equation and a NFW+Sersic mass density profile reproduces the observed signal deficit, strongly supporting that the Einstein Gap is a strong lensing feature: background sources within the Einstein radius are displaced outward, creating a characteristic empty annulus whose angular size scales. This feature is consistent with features visible in previously published weak-lensing profiles that were not, however, interpreted as a strong-lensing signature. Its identification opens new possibilities for constraining halo masses and concentrations from magnification bias measurements alone.

astro-ph.GA↗
arXiv2026

Starbursts hiding in the main sequence: a pathway toward quenching?

Star-forming galaxies spend most of their lifetimes on the star-forming main sequence, which establishes a tight empirical and statistical relation between stellar mass and star-formation rate. Occasional episodes of rapid star formation can push them temporarily above this sequence, turning them into starbursts. Yet some galaxies display starburst-like traits -- rapid, dense, and compact star formation -- while still remaining within the scatter of the main sequence. These "starbursts in the main sequence" (SBMSs) reveal the complexity and diversity of star formation modes, making them crucial for understanding how galaxies evolve and transition between different regimes. In this paper, we identify SBMSs in the cosmological simulation NewHorizon and follow their evolution across time to uncover their physical origins and the role of this special regime in shaping galaxy evolution. We explain the existence of SBMSs by a comparatively earlier assembly of their stellar mass, driven in particular by more frequent and repeated mergers as the other galaxies, as well as exceptionally productive starburst events triggered by these interactions. As a result, this regime appears preferentially -- though not exclusively -- in the most massive galaxies. The SBMS behavior is not continuous within individual galaxies but instead arises intermittently as a short-lived (~ 30 Myr) evolutionary mode. Nevertheless, such SBMS episodes exist throughout cosmic time across the galaxy population... [abridged]

astro-ph.GA↗