Using the first scientific image released by the James Webb Space Telescope (JWST) this month, an international team led by scientists from the Max Planck Institute for Astrophysics (MPA) and the Technical University of Munich (TUM) has built an improved model for in the mass distribution of the galaxy cluster SMACS J0723.3−7327. They used dozens of multiple images of distant background galaxies revealed in the JWST image, some of which were too faint to be previously detected. Acting as a so-called gravitational lens, the foreground galaxy cluster produces multiple images of background galaxies and magnifies these images. One family of these multiple images belongs to a galaxy, which the model predicts is about 13 Gyrs away, meaning its light traveled about 13 billion years before reaching the telescope .
The first scientific image released by the James Webb Space Telescope (JWST) was of gravitational lensing, in particular of the galaxy cluster SMACS J0723.3−7327. Gravitational lensing, especially by galaxy clusters, magnifies the light of background galaxies and produces multiple images of them. Before JWST, 19 multiple images of six background sources were known in SMACS J0723.3−7327. The JWST data now revealed an additional 27 multiple images from ten other lensed sources.
“In this first step towards the road opened by JWST, we have used recent data from this new telescope, to model the lensing effect of SMACS0723 with great precision,” notes Gabriel Bartosch Caminha, postdoctoral researcher at the Max Planck Institute of Astrophysics (MPA), the Technical University of Munich and the German Center for Cosmological Lenses (GCCL). The collaboration first used data from the Hubble Space Telescope (HST) and the Multiple Unit Spectroscopic Explorer (MUSE) to build a “pre-JWST” lens model, then refined it with infrared images upcoming newly available JWSTs. “The JWST image is absolutely stunning and beautiful, showing many more multi-lensed background sources, which allowed us to substantially refine our lensing mass model,” he adds.
Many of these new lensed sources do not yet have distance estimates, and the scientists used their mass model to predict how far away these lensed galaxies are most likely to be. One of them was found to be probably at a surprising distance of 13 Gyrs (redshift > 7.5), meaning its light was emitted during the early stages of the Universe. This galaxy is multiplied in three images and its luminosity is magnified by a factor of μ≈20 in total.
However, to study these primordial objects, it is critical to accurately describe the lensing effect of the foreground galaxy cluster. “Our accurate mass model forms the basis for the exploration of the JWST data,” emphasizes Sherry Suyu, professor of observational cosmology at TUM, leader of the Max Planck research group at MPA and visiting researcher at the Institute of Astronomy and Astrophysics of the Sinica Academy. “The spectacular JWST images show a wide variety of strongly lensed galaxies, which can be studied in detail thanks to our accurate model.”
The new model for the mass distribution of the foreground cluster is able to reproduce the positions of all multiple images with high accuracy, making the model one of the most accurate available. For follow-up studies of these sources, lensing models, including magnification maps and redshifts (i.e. distances) estimated from the model, are made publicly available. “We are very excited about this,” adds Suyu, “we are looking forward to future JWST observations of other strong lensing galaxy clusters. This will not only allow us to better constrain the mass distributions of galaxy clusters, but also study the galaxies at high redshift”.
Title of the article
First JWST observations of a gravitational lens: new multi-image massive model with near-infrared observations of SMACS ~ J0723.3−7327
Publication date of the article
July 15, 2022
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