Letter to the Editor

A search for dust and molecular gas in enormous Lyα nebulae at z ≈ 2

¹ INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Gobetti 93/3, 40129 Bologna, Italy
e-mail: roberto.decarli@inaf.it
² Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str 1, 85748 Garching bei München, Germany
³ Department of Physics, Broida Hall, University of California, Santa Barbara, CA 93106-9530, USA
⁴ Max-Planck Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁵ UCO/Lick Observatory, University of California Santa Cruz, Santa Cruz, CA 95064, USA
⁶ Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), 5-1-5 Kashiwanoha, Kashiwa 277-8583, Japan
⁷ Department of Physics, ETH Zurich, Wolgang-Pauli-Strasse 27, 8093 Zürich, Switzerland
⁸ Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126 Milano, Italy

Received: 30 October 2020
Accepted: 8 December 2020

Abstract

Enormous Lyα nebulae, extending over 300−500 kpc around quasars, represent the pinnacle of galaxy and cluster formation. Here we present IRAM Plateau de Bure Interferometer observations of the enormous Lyα nebulae “Slug” (z = 2.282) and “Jackpot” (z = 2.041). Our data reveal bright, synchrotron emission associated with the two radio-loud active galactic nuclei embedded in the targeted nebulae as well as molecular gas, as traced via the CO(3−2) line, in three galaxies (two sources in Slug, and one in Jackpot). All of the CO emission is associated with galaxies detected in their rest-frame UV stellar emission. The total mass in molecular gas of these three galaxies [∼(3 − 5) × 10¹⁰ M_⊙] is comparable with the total ionized gas mass responsible for the diffuse nebular emission. Our observations place limits on the molecular gas emission in the nebulae: the molecular gas surface density is Σ_H2 <  12 − 25 M_⊙ pc⁻² for the Slug nebula and Σ_H2 <  34 − 68 M_⊙ pc⁻² for the Jackpot nebula. These are consistent with the expected molecular gas surface densities, as predicted via photoionization models of the rest-frame UV line emission in the nebulae, and via Lyα absorption in the Jackpot nebula. Compared to other radio-loud quasars at z >  1 and high-redshift radio-loud galaxies, we do not find any strong trends relating the molecular gas reservoirs, the radio power, and the Lyα luminosities of these systems. The significant step in sensitivity required to achieve a detection of the molecular gas from the nebulae, if present, will require a substantial time investment with JVLA, NOEMA, or ALMA.