Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have discovered a rotating dwarf galaxy 1/100th the size of the Milky Way in the early Universe.
This composite image, taken by the NASA/ESA Hubble Space Telescope and ALMA, shows the galaxy cluster RXCJ0600-2007 and lensed images of the galaxy RXCJ0600-z6 (red). Image credit: ALMA / ESO / NAOJ / NRAO / Fujimoto et al. / NASA / ESA / Hubble Team.
The newfound lensed galaxy is located in the constellation of Lepus and is seen at a time when the Universe was only 7% of its current age, just 900 million years after Big Bang.
Named RXCJ0600-z6, the galaxy has a mass between 2 and 3 billion solar masses.
“Many of the galaxies that existed in the early Universe were so small that their brightness is well below the limit of the current largest telescopes on Earth and in space, making difficult to study their properties and internal structure,” said Dr. Nicolas Laporte, an astronomer at the University of Cambridge.
“However, the light coming from RXCJ0600-z6 was highly magnified by gravitational lensing, making it an ideal target for studying the properties and structure of a typical baby galaxies.”
During the ALMA Lensing Cluster Survey (ALCS), Dr. Laporte and colleagues searched for galaxies in the early Universe that are magnified by gravitational lensing.
They performed a large-scale program that took 95 hours to observe the central regions of 33 galaxy clusters that could cause gravitational lensing.
They discovered a multiply-imaged galaxy, RXCJ0600-z6, strongly magnified by the massive galaxy cluster RXCJ0600-2007.
By combining data from the NASA/ESA Hubble Space Telescope and ESO’s Very Large Telescope with a theoretical model, they succeeded in reconstructing the actual shape of the distant galaxy.
What astonished the astronomers is that RXCJ0600-z6 is rotating.
“Our study demonstrates, for the first time, that we can directly measure the internal motion of such faint (less massive) galaxies in the early Universe and compare it with the theoretical predictions,” said Professor Kotaro Kohno, an astronomer at the University of Tokyo.
“The fact that RXCJ0600-z6 has a very high magnification factor also raises expectations for future research,” said Dr. Seiji Fujimoto, an astronomer at the Niels Bohr Institute.
The findings appear in two papers in the Astrophysical Journal and the Monthly Notices of the Royal Astronomical Society.
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Seiji Fujimoto et al. 2021. ALMA Lensing Cluster Survey: Bright [CII] 158 μm Lines from a Multiply Imaged Sub-L* Galaxy at z=6.0719. ApJ 911, 99; doi: 10.3847/1538-4357/abd7ec
N. Laporte et al. ALMA Lensing Cluster Survey: a strongly lensed multiply imaged dusty system at z ≥6. MNRAS, published online January 28, 2021; doi: 10.1093/mnras/stab191
