A pilot sample of Planck-selected strongly lensed sub-mm galaxies: NOEMA observations and physical characterisation

Leonardo Trobbiani; Matteo Bonato; Ivano Baronchelli; Gianfranco De Zotti; Mattia Negrello; Marika Giulietti; Stefano Berta; Cristian Vignali; Marcella Massardi

arXiv · 2607.19478

A pilot sample of Planck-selected strongly lensed sub-mm galaxies: NOEMA observations and physical characterisation

Leonardo Trobbiani·Matteo Bonato·Ivano Baronchelli·Gianfranco De Zotti·Mattia Negrello·Marika Giulietti·Stefano Berta·Cristian Vignali·Marcella Massardi

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Abstract

The extreme brightness of high-$z$ strongly lensed galaxies detected by Planck surveys, thanks to their exceptionally large gravitational magnifications, offers a unique opportunity to investigate in extraordinary detail their structure and kinematics during their active star-formation phase. As a step in this direction, we present and analyse NOEMA imaging and spectroscopic data for four lensed high-z galaxy candidates. We performed continuum and line imaging of the sources at 2 and 3 mm bands down to $1''.2$ spatial resolution and 40 $\rm{km}\,{\rm s}^{-1}$ spectral resolution, reconstructed and fitted the line profiles, and produced moment maps of the line emission to investigate the spatial distribution and kinematics of the molecular gas. We also carried out the gravitational lens modelling for one of the sources. The continuum images showed multiple components for at least two of the sources, strongly supporting the strong lensing scenario. We detected with high S/N ratios two CO lines for all sources, at CO(3-2), CO(4-3) and CO(5-4) transitions; for one source, we also detected the [CI](1-0) line. We derived accurate spectroscopic redshifts $2.3 \lesssim z \lesssim 3.3$, with $1\sigma$ uncertainties $\delta z \approx 10^{-4}$ in redshift. All four sources lie well above the CO line luminosity-linewidth relation for unlensed galaxies, providing independent confirmation of their strongly lensed nature. Three sources exhibit broad (FWHM$\gtrsim 400\,{\rm km}\,{\rm s}^{-1}$), double-peaked line profiles and substantial velocity gradients, while the last one shows relatively narrow, single-peaked lines and no detectable velocity gradients, possibly indicating a nearly face-on geometry or intrinsically simple kinematics.

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Leonardo Trobbiani, Matteo Bonato, Ivano Baronchelli, Gianfranco De Zotti, Mattia Negrello, Marika Giulietti, Stefano Berta, Cristian Vignali, Marcella Massardi. 2026-07-21. A pilot sample of Planck-selected strongly lensed sub-mm galaxies: NOEMA observations and physical characterisation. https://arxiv.org/abs/2607.19478

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