Probing the warm dark matter mass with [C II] intensity mapping

Marcuzzo, Elena, Porciani, Cristiano, Romano-Díaz, Emilio, Moradinezhad Dizgah, Azadeh, Khatri, Prachi and Viel, Matteo 2026. Probing the warm dark matter mass with [C II] intensity mapping. Astronomy & Astrophysics 707 , A148. 10.1051/0004-6361/202558473

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Abstract

Context. The nature of dark matter (DM) is still debated. While cold DM (CDM) is the standard paradigm, warm DM (WDM) composed of thermal relics may ease some small-scale tensions in the ΛCDM framework. Line-intensity mapping (LIM) offers a novel probe of DM properties. Aims. To explore the potential of LIM surveys in constraining the WDM particle mass ( m WDM ) by means of the [C II ] power spectrum (PS), we provide forecasts for the Deep Spectroscopic Survey (DSS) to be performed with the Fred Young Submillimeter Telescope at z ≃ 3.6 and extend the analysis to larger sky coverage, higher sensitivity, and/or increased spectral resolution. Methods. We developed a formulation for the [C II ] PS based on the halo-model approach, incorporating the uncertainty in the luminosity function (LF) through two alternative parameterisations, one optimistic and the other more conservative. We performed a Bayesian analysis on mock data to derive constraints on m WDM . Results. In a CDM universe, the DSS yields lower limits on m WDM , at a 95% credibility level, of 1.10 keV and 0.58 keV when considering the optimistic and pessimistic LF ( α = −1.1), respectively. Ambitious surveys can improve these figures to 5.82 keV and 1.90 keV, and assuming a steeper faint-end slope ( α = −1.9) further boosts the constraints even beyond those obtained in the optimistic scenario. A fivefold increase in spectral resolution enhances sensitivity to the damping scale associated with redshift-space distortions, tightening the constraints on m WDM by a factor of up to ∼1.8. Finally, Bayesian inference on mock data with m WDM = 3 keV results in a well-constrained and unbiased posterior only in futuristic survey setups. Conclusions. Upcoming LIM surveys can provide meaningful limits on m WDM , although the negligible contribution from small haloes reduces the constraining power of the [C II ] PS. Future progress will benefit from combining multiple redshifts and emission lines, opening the way to competitive constraints on the nature of DM.

Item Type:	Article
Date Type:	Published Online
Status:	Published
Schools:	Schools > Physics and Astronomy
Additional Information:	License information from Publisher: LICENSE 1: URL: https://creativecommons.org/licenses/by/4.0, Start Date: 2026-03-04
Publisher:	EDP Sciences
ISSN:	0004-6361
Date of First Compliant Deposit:	16 March 2026
Date of Acceptance:	12 January 2026
Last Modified:	16 Mar 2026 10:45
URI:	https://orca.cardiff.ac.uk/id/eprint/185757

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