Molecular gas and star formation activity in luminous infrared galaxies in clusters at intermediate redshifts

¹ Laboratoire d’Astrophysique, École Polytechnique Fédérale de Lausanne (EPFL), Observatoire de Sauverny, 1290 Versoix, Switzerland
e-mail: gianluca.castignani@epfl.ch
² Observatoire de Paris, GEPI, CNRS, Sorbonne University, PSL Research University, 75014 Paris, France
³ Observatoire de Paris, LERMA, CNRS, Sorbonne University, PSL Research University, 75014 Paris, France
⁴ Collège de France, 11 Place Marcelin Berthelot, 75231 Paris, France
⁵ Universidad de Atacama, Instituto de Astronomía y Ciencias Planetarias de Atacama, Av. Copayapu 485, Copiapó, Región de Atacama, Chile
⁶ ESA, Science Operations Department, STScI, Baltimore, MD 21218, USA
⁷ Centre for Extragalactic Astronomy, Durham University, South Road, Durham DH1 3LE, UK
⁸ Institute for Computational Cosmology, Durham University, South Road, Durham DH1 3LE, UK
⁹ Astrophysics and Cosmology Research Unit, School of Mathematical Sciences, University of KwaZulu-Natal, Durban 4041, South Africa
¹⁰ Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721, USA
¹¹ IRAM, Domaine Universitaire, 300 Rue de la Piscine, 38406 Saint-Martin-d’Hères, France
¹² Laboratoire AIM, IRFU/Service d’Astrophysique-CEA – CNRS, Université Paris Diderot, Gif-sur-Yvette, France
¹³ Observatorio Astronómico Nacional (OAN-IGN)-Observatorio de Madrid, Alfonso XII, 3, 28014 Madrid, Spain
¹⁴ MPI for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
¹⁵ Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany

Received: 26 November 2019
Accepted: 17 May 2020

Abstract

We investigate the role of dense megaparsec-scale environments in processing molecular gas of cluster galaxies as they fall into the cluster cores. We selected a sample of ∼20 luminous infrared galaxies (LIRGs) belonging to intermediate-redshift clusters, mainly from the Herschel Lensing Survey and the Local Cluster Substructure Survey. These galaxies include MACS J0717.5+3745 at z = 0.546 and Abell 697, 963, 1763, and 2219 at z = 0.2 − 0.3. We performed spectral energy distribution modeling from the far-infrared to ultraviolet of the LIRGs, which span cluster-centric distances within r/r₂₀₀ ≃ 0.2 − 1.6. We observed the LIRGs in CO(1→0) or CO(2→1) with the Plateau de Bure interferometer and its successor NOEMA, as part of five observational programs carried out between 2012 and 2017. We compared the molecular gas to stellar mass ratio M(H₂)/M_⋆, star formation rate (SFR), and depletion time (τ_dep) of the LIRGs with those of a compilation of cluster and field star-forming galaxies from the literature. The targeted LIRGs have SFR, M(H₂)/M_⋆, and τ_dep that are consistent with those of both main-sequence (MS) field galaxies and star-forming galaxies from the comparison sample. However we find that the depletion time, normalized to the MS value, tentatively increases with increasing r/r₂₀₀, with a significance of 2.8σ, which is ultimately due to a deficit of cluster-core LIRGs with τ_dep ≳ τ_dep, MS. We suggest that a rapid exhaustion of the molecular gas reservoirs occurs in the cluster LIRGs and is indeed effective in suppressing their star formation and ultimately quenching them. This mechanism may explain the exponential decrease of the fraction of cluster LIRGs with cosmic time. The compression of the gas in LIRGs, possibly induced by intra-cluster medium shocks, may be responsible for the short timescales that are observed in a large fraction of cluster-core LIRGs. Some of our LIRGs may also belong to a population of infalling filament galaxies.