Astronomers from the Max Planck Institute for Astrophysics and elsewhere have analyzed an image taken by the NASA/ESA/CSA James Webb Space Telescope of SMACS J0723.3-7327, a massive cluster of galaxies within the southern constellation of Volans.
This Webb image shows multiply lensed background galaxies around SMACS J0723.3-7327 (cyan indicates already known multiple image systems; green indicates new multiply lensed sources); the insets show enlarged images of a very distant galaxy with some substructure indicated by the green arrows. Image credit: NASA / ESA / CSA / STScI / Max Planck Institute for Astrophysics.
Galaxy clusters contain thousands of galaxies of all ages, shapes and sizes.
These structures have a mass of about one million billion times the mass of the Sun and form over billions of years as smaller groups of galaxies slowly come together.
Albert Einstein predicted in his theory of general relativity that massive objects will deform the fabric of space itself.
When light passes one of these objects, such as a massive galaxy cluster, its path is changed slightly.
Called gravitational lensing, this effect is only visible in rare cases and only world’s best telescopes can observe the related phenomena.
The magnifying properties of gravitational lensing allow astronomers to study objects that would not be visible otherwise and to directly compare local galaxies with much more remote ones, seen when the Universe was significantly younger.
“In the first step towards the road opened by Webb, we used recent data from this brand new telescope to model the lensing effect of the galaxy cluster SMACS J0723.3-7327 (also known as SMACS 0723 or PSZ1 G284.97-23.69) with great accuracy,” said Dr. Gabriel Bartosch Caminha, an astronomer at the Max Planck Institute for Astrophysics, the Technical University Munich, and the German Centre for Cosmological Lensing.
In their study, Dr. Bartosch Caminha and colleagues used data from the NASA/ESA Hubble Space Telescope and the Multi Unit Spectroscopic Explorer (MUSE) instrument on ESO’s Very Large Telescope to build a ‘pre-Webb’ lens model and then refined it with the recently released near-infrared images of SMACS J0723.3-7327.
“The Webb imaging is absolutely astounding and beautiful, showing many more multiply lensed background sources, which allowed us to substantially refine our lens mass model,” Dr. Bartosch Caminha said.
This Webb image shows the galaxy cluster SMACS J0723.3-7327. Image credit: NASA / ESA / CSA / STScI.
Before Webb, 19 multiple images of six background sources were known in SMACS J0723.3-7327.
The new Webb data revealed 27 additional multiple images from 10 previously undetcted gravitationally lensed objects.
“Many of these new sources do not yet have distance estimates, and we used our mass model to predict how far away these lensed galaxies are most likely to be,” the astronomers said.
“One of them was found to be probably at the amazing distance of 13 billion years (redshift > 7.5), i.e. its light was emitted during the Universe’s early stages.”
“This galaxy is multiply lensed into three images and its luminosity is magnified by a factor of 20 in total.”
“Our accurate mass model forms the foundation for the exploration of the Webb data,” said Dr. Sherry Suyu, an astronomer at the Max Planck Institute for Astrophysics, the Technical University Munich, and the Academia Sinica Institute of Astronomy and Astrophysics.
“The spectacular Webb images show a great variety of strongly lensed galaxies, which can be studied in detail thanks to our accurate model.”
“We are very excited about this; we are eagerly awaiting future Webb observations of other strong lensing galaxy clusters.”
“These will not only allow us to better constrain the mass distributions of galaxy clusters, but also to study high-redshift galaxies.”
The team’s paper will be published in the journal Astronomy & Astrophysics.
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G.B. Caminha et al. 2022. First JWST observations of a gravitational lens: Mass model of new multiple images with near-infrared observations of SMACS J0723.3-7327. A&A, in press; arXiv: 2207.07567
