James Webb Space Telescope identifies the farthest Milky Way-like galaxy ever observed

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Artistic representation of the barred spiral galaxy ceers-2112, with a structure
Artistic representation of the barred spiral galaxy ceers-2112, with a structure similar to the Milky Way, observed in the early Universe. Earth is reflected in a bubble surrounding ceers-2112, recalling the connection between our galaxy and ceers-2112. Credits: Luca Costantin (CAB/CSIC-INTA).

An international scientific team, led by the Center for Astrobiology (CAB), CSIC-INTA and including Cristina Cabello, postdoctoral researcher at the Institute of Particle Physics and Cosmos of the Complutense University of Madrid (IPARCOS-UCM), has discovered the most distant Milky Way-like barred galaxy known to date.

The current age of the Universe is around 13.8 billion years, and until now scientists thought that the structure of spiral galaxies like our Milky Way galaxy did not consolidate until the Universe was half its current age. "Contrary to expectations, this discovery reveals that galaxies similar to the Milky Way already existed 11.7 billion years ago," says Luca Costantin , CSIC postdoctoral researcher at the CAB in Madrid and lead author of the paper.

By studying the structure of galaxies at different distances (i.e., at different ages in the Universe), scientists are trying to reconstruct the formation and evolutionary history of the Milky Way. In the nearby Universe, most massive spiral galaxies show an elongated bar-shaped structure in their central regions, just like our own galaxy. On the contrary, according to the predictions of theoretical models, physical conditions

and dynamics of the early Universe inhibit or delay the formation of bars in the youngest and most distant galaxies. Galactic bars play a fundamental role in the evolution of galaxies, since they favor the mixing of elements, which is essential for the formation of stars (such as the Sun).

"Galaxies have not always been as we observe them around us, as they vary in mass and structure throughout their lifetimes. Although Milky Way-like barred galaxies are common in the nearby Universe, until now we thought they should be extremely rare when we look back in time," says Cristina Cabello, postdoctoral researcher at the Institute of Particle and Cosmos Physics of the Complutense University of Madrid (IPARCOS-UCM).

From the observational point of view, until now the knowledge about the morphology of distant galaxies has been based mainly on studies carried out with the Hubble space telescope, which revealed very irregular structures, the result of possible mergers between galaxies. However, the extraordinary capabilities of the James Webb Space Telescope (JWST) are revolutionizing astrophysics, revealing that the distant Universe is not exactly as scientists expected."With the James Webb Space Telescope we have for the first time the technology and instrumentation needed to study in detail the morphology of very distant galaxies. Investigating how galaxies acquire the structure that characterizes them today is essential to understand the formation and evolution of galaxies," says Pablo G. Pérez González, INTA research scientist at the CAB in Madrid and professor on leave of absence at the UCM.

Using the JWST, an international scientific team led by the CAB and involving the Universidad Complutense de Madrid, has discovered a galaxy in the early Universe that already has one of the most characteristic structures of the Milky Way, the so-called barred galaxy. The barred spiral galaxy (called ceers-2112) is at a redshift of 3, i.e., when the Universe was only 2.1 billion years old, which defies previous knowledge of galaxy formation.

The discovery together with the detailed analysis has been published in the journal Nature."ceers-2112 is considered a galaxy analogous to the Milky Way, since it presents a barred spiralstructure and the same mass that our galaxy must have had at that instant of the Universe," explains Luca Costantin. "Surprisingly, this finding proves that when the Universe was still very young, the evolution of this galaxy was dominated by baryons (the ordinary matter of which we are composed) and not by dark matter, although it is more abundant," adds Jairo Méndez Abreu, a researcher at the Instituto de Astrofísica de Canarias and the University of La Laguna.

The bar of the ceers-2112 galaxy has been identified thanks to the analysis of images taken with the NIRCam instrument of the JWST. The scientific data were taken during observations of the CEERS project(Cosmic Evolution Early Release Science, led by Steven L. Finkelstein of the University of Texas, USA) within the Extended Groth Strip, a region of the sky located between the constellations Ursa Major and Buoyant. The project involved 33 researchers from 29 institutions in 8 countries. The detection of the bar was carried out using several complex structure analysis methods, such as modeling the light of the galaxy at different wavelengths or studying the spatial variations of the symmetric components (Fourier analysis).

Article : "A Milky Way-like barred spiral galaxy at a redshift of 3", Costantin et al. 2023, Nature, ’ 023 -06636-x

Contacts: Cristina Cabello, postdoctoral researcher at IPARCOS-UCM: criscabe@ucm.es Luca Costantin, postdoctoral researcher at CAB CSIC-INTA: lcostantin@cab.inta-csic.es

Artistic representation of the barred spiral galaxy ceers-2112, with a structure similar to the Milky Way, observed in the early Universe. Earth is reflected in a bubble surrounding ceers-2112, recalling the connection between our galaxy and ceers-2112. Credits: Luca Costantin (CAB/CSIC-INTA).

Members of the research team responsible for the discovery, Dr. Cristina Cabello (IPARCOS-UCM) and Dr. Luca Costantin (CAB/CSIC-INTA).