Let the show begin: APEX’s CONCERTO instrument sees first light

An exciting new instrument, a spectrometer called CONCERTO, has successfully produced its first observations: test images of the Cat’s Paw Nebula and the Crab Nebula. The instrument, installed on the ESO-operated Atacama Pathfinder Experiment (APEX), will help astronomers probe the mysterious, ancient cosmic epoch during which the first stars lit up.

The main goal of CONCERTO, which stands for CarbON CII line in post-rEionisation and ReionisaTiOn epoch, is to study the birth of the first generation of stars. To do so, it will look at cosmic objects that formed between 600 million and 1.2 billion years after the Big Bang. This era, known as cosmic reionisation, is poorly understood yet crucial in the history of the cosmos, as it marks the transition between the “dark ages” — a very obscure period in the life of the Universe in which stars had not formed yet — and the time when the most distant galaxies we see in the Universe today formed. CONCERTO will also map distant galaxy clusters and star-forming regions in our Milky Way.

As an instrument that is able to scan the sky at frequencies between infrared and radio waves, CONCERTO will look at radiation emitted by ionised carbon atoms, one of the most valuable tracers of star formation in the early cosmic ages. “The objective of shedding light on the reionisation period is very hard, as the signal we are searching for is very small,” says CONCERTO’s Principal Investigator Guilaine Lagache from the Laboratoire d’Astrophysique de Marseille, in France. “We will tackle this by using a totally innovative and experimental observing technique, called intensity mapping. CONCERTO will be the first instrument in the world to perform intensity mapping of the primordial carbon radiation on a large field of the sky.”

“CONCERTO is completely unique at APEX,” says ESO Astronomer and APEX Project Scientist Carlos De Breuck. “The other instruments either concentrate on imaging or spectroscopy, but not on both like CONCERTO is doing. And in terms of imaging, with a diameter of about 20 arcminutes on sky, it is by a margin the largest field-of-view ever used at APEX.” The new instrument has replaced the LArge APEX BOlometer CAmera (LABOCA), enabling a four-time improvement in terms of field of view.

CONCERTO’s first light marks the end of its installation process, which started with the delivery of the instrument to the APEX site in the Chanjantor plateau in the Chilean Atacama Desert in late March 2021.

The COVID-19 pandemic posed a considerable challenge to the CONCERTO team, who managed to prepare the instrument for fully remote operations, ship it to Chile, and install it at APEX under strict health and safety conditions. “A large part of this success comes from the team spirit and the fact that we all work with passion and determination,” says CONCERTO’s instrument scientist Alessandro Monfardini from Institut Néel in Grenoble, France. The team is also grateful to the local APEX staff for their dedication and help installing and testing the instrument.

More Information

CONCERTO received funding from the European Research Council under grant agreement No 788212, from the Aix-Marseille Initiative of Excellence (France) and LabEx FOCUS (France). The institutes involved in the CONCERTO consortium are the Laboratoire d’Astrophysique de Marseille (LAM; France), the Institut Néel (France), the Laboratoire de Physique Subatomique et de Cosmologie (LPSC; France), the Institut de Planétologie et d’Astrophysique (IPAG; France) and the Astronomy Instrumentation Group at the University of Cardiff (United Kingdom). The Institut Néel, LPSC and IPAG are laboratories of the Centre National de la Recherche Scientifique (CNRS) and the Université Grenoble Alpes (UGA). LAM is a laboratory of the CNRS and the Aix-Marseille University.

APEX is a collaboration between the Max Planck Institute for Radio Astronomy (MPIfR), the Onsala Space Observatory (OSO) and ESO. Operation of APEX at Chajnantor is entrusted to ESO.

Courtesy of European Southern Observatory