ALMA Lensing Cluster Survey: An ALMA Galaxy Signposting a MUSE Galaxy Group at z=4.3 Behind "El Gordo"
Journal article, 2021

We report the discovery of a Multi Unit Spectroscopic Explorer (MUSE) galaxy group at z = 4.32 lensed by the massive galaxy cluster ACT-CL J0102-4915 (aka El Gordo) at z = 0.87, associated with a 1.2 mm source that is at a 2.07 0.88 kpc projected distance from one of the group galaxies. Three images of the whole system appear in the image plane. The 1.2 mm source has been detected within the Atacama Large Millimetre/submillimetre Array (ALMA) Lensing Cluster Survey (ALCS). As this ALMA source is undetected at wavelengths lambda < 2 mu m, its redshift cannot be independently determined, however, the three lensing components indicate that it belongs to the same galaxy group at z = 4.32. The four members of the MUSE galaxy group have low to intermediate stellar masses (similar to 10(7)-10(10) M) and star formation rates (SFRs) of 0.4-24 M yr(-1), resulting in high specific SFRs (sSFRs) for two of them, which suggest that these galaxies are growing fast (with stellar mass doubling times of only similar to 2 x 10(7) yr). This high incidence of starburst galaxies is likely a consequence of interactions within the galaxy group, which is compact and has high velocity dispersion. Based on the magnification-corrected sub-/millimeter continuum flux density and estimated stellar mass, we infer that the ALMA source is classified as an ordinary ultra-luminous infrared galaxy (with associated dust-obscured SFR similar to 200-300 M yr(-1)) and lies on the star formation main sequence. This reported case of an ALMA/MUSE group association suggests that some presumably isolated ALMA sources are in fact signposts of richer star-forming environments at high redshifts.

Submillimeter astronomy

Galaxy groups

Starburst galaxies

High-redshift galaxies


K. I. Caputi

University of Groningen

University of Copenhagen

G. B. Caminha

University of Groningen

S. Fujimoto

University of Copenhagen

K. Kohno

University of Tokyo

F. Sun

University of Arizona

E. Egami

University of Arizona

S. Deshmukh

University of Groningen

F. Tang

University of Groningen

Y. Ao

Chinese Academy of Sciences

University of Science and Technology of China

L. Bradley

Space Telescope Science Institute (STScI)

D. Coe

Space Telescope Science Institute (STScI)

D. Espada

SKA Organisation

C. Grillo

Istituto nazionale di astrofisica (INAF)

University of Milan

University of Copenhagen

B. Hatsukade

University of Tokyo

Kirsten Kraiberg Knudsen

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

M. M. Lee

Max Planck Society

G. E. Magdis

Technical University of Denmark (DTU)

University of Copenhagen

K. Morokuma-Matsui

University of Tokyo

P. Oesch

University of Geneva

M. Ouchi

National Astronomical Observatory of Japan

University of Tokyo

P. Rosati

INAF OAS Bologna

University of Ferrara

H. Umehata


University of Tokyo

F. Valentino

University of Copenhagen

E. Vanzella

INAF OAS Bologna

W. -H. Wang

Academia Sinica

J. F. Wu

Space Telescope Science Institute (STScI)

A. Zitrin

Ben-Gurion University of the Negev

Astrophysical Journal

0004-637X (ISSN) 1538-4357 (eISSN)

Vol. 908 2 146

Subject Categories

Astronomy, Astrophysics and Cosmology


Computer Vision and Robotics (Autonomous Systems)



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3/9/2021 3