Science

Astronomers Study ‘Molten Einstein Ring’ in Detail

Located in the southern constellation of Fornax, GAL-CLUS-022058-38303 is a so-called Einstein ring — a distorted image of a gravitationally lensed distant galaxy. In December 2020, the Hubble team released the image of the object as an example of one of the largest, nearly complete Einstein rings ever seen. GAL-CLUS-022058-38303 was nicknamed the ‘Molten Ring’ by the Hubble astronomers, which alludes to its appearance and host constellation. Using data from Hubble and the FORS instrument on ESO’s Very Large Telescope, astronomers have now studied GAL-CLUS-022058-38303 in detail.

This Hubble image shows GAL-CLUS-022058-38303, the largest, nearly-complete Einstein ring known. The image is made up of observations from Hubble’s Wide Field Camera 3 (WFC3) in the infrared and optical parts of the spectrum. Three filters were used to sample various wavelengths. The color results from assigning different hues to each monochromatic image associated with an individual filter. Image credit: NASA / ESA / Hubble / Saurabh Jha, Rutgers the State University of New Jersey / L. Shatz.

This Hubble image shows GAL-CLUS-022058-38303, the largest, nearly-complete Einstein ring known. The image is made up of observations from Hubble’s Wide Field Camera 3 (WFC3) in the infrared and optical parts of the spectrum. Three filters were used to sample various wavelengths. The color results from assigning different hues to each monochromatic image associated with an individual filter. Image credit: NASA / ESA / Hubble / Saurabh Jha, Rutgers the State University of New Jersey / L. Shatz.

“In order to derive the physical properties of the lensed galaxy a lensing model is needed,” said Dr. Anastasio Díaz-Sánchez, an astronomer at the Universidad Politécnica de Cartagena.

“Such a model could only be obtained with the Hubble imaging.”

“In particular, Hubble helped us to identify the four counter images and the stellar clumps of the lensed galaxy.”

From this lensing model, Dr. Díaz-Sánchez and colleagues calculated the amplification factor, which is a valuable effect of gravitational lensing.

This allowed the astronomers to study the intrinsic physical properties of the lensed galaxy.

Of particular interest is the determination of the galaxy’s distance, which shows that the galaxy’s light has traveled approximately 9.4 billion light-years.

“The detection of molecular gas, of which new stars are born, allowed us to calculate the precise redshift and thus gives us confidence that we are truly looking at a very distant galaxy,” said Nikolaus Sulzenauer, a Ph.D. student at the Max Plank Institute for Radio Astronomy.

The researchers also determined the galaxy’s magnification factor to be 20, which effectively makes the Hubble’s observing capability equivalent to that of a 48-m telescope.

“The lensed galaxy is one of the brightest galaxies in the millimeter wavelength regime,” said Dr. Helmut Dannerbauer, an astronomer at the Institute of Astrophysics of the Canary Islands.

“Our research has also shown that it is a normal star-forming galaxy — a so-called main sequence galaxy — at the peak epoch of star formation in the Universe.”

“We can clearly see the spiral arms and the central bulge of the galaxy in the Hubble images,” added Dr. Susana Iglesias-Groth, also from the Institute of Astrophysics of the Canary Islands.

“This will help us to better understand star formation in distant galaxies using planned observations.”

A paper on the findings was published in the Astrophysical Journal.

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A. Díaz-Sánchez et al. 2021. The Einstein ring GAL-CLUS-022058s: a Lensed Ultrabright Submillimeter Galaxy at z=1.4796. ApJ, in press; doi: 10.3847/1538-4357/ac0f75

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