Morphology and photometric redshift of Zhúlóng. Credit: Xiao et al., 2024.
An international team of astronomers used the James Webb Space Telescope (JWST) to detect a new grand design spiral galaxy as part of a panoramic survey. The newly discovered galaxy, named Zhúlóng, is so massive that it appears to be the most distant spiral galaxy yet identified. The findings are detailed in a paper published Dec. 17 on the preprint server arXiv.
Grand Design spiral galaxies are characterized by distinct, well-defined arms that swirl outward from a transparent core. It is thought that the arms of such galaxies are actually dense regions of the disk where incoming material is compressed, causing star formation.
It is still not well understood when and how spiral galaxies appeared in the early Universe, and such galaxies are generally rare at large redshifts. To date, only a few individual spirals with redshifts above 3.0 have been found.
Now, a group of astronomers led by Mengyuan Xiao at the University of Geneva in Switzerland report the serendipitous detection of a new high-redshift grand design spiral galaxy using JWST. This galaxy was named Zhúlóng, after the giant red sun dragon and god from Chinese mythology.
“Zhúlóng (α, δ (J2000) = 150.124874, 2.092919) was accidentally discovered in the field j100024p0208 in the recent data release of the JWST PANORAMIC survey, a pure parallel extragalactic NIRCam imaging program.” the researchers wrote.
According to the study, Zhúlóng was identified with a photometric redshift of approximately 5.2. Its mass was found to be comparable to that of the Milky Way, which is relatively large for a galaxy that formed less than a billion years after the Big Bang, as indicated by its redshift.
The study found that Zhúlóng has a classical bulge and a large face-on stellar disk with spiral arms extending over 62,000 light-years. Spectral energy distribution (SED) analysis shows a quiescent core and a star-forming stellar disk.
Furthermore, compared to the stellar disk, Zhúlóng’s core was found to be red and have the highest surface density of stellar mass measured among quiescent galaxies. The core is stationary, consistent with the expectation that galaxies grow and die from the inside out.
The study also found that although the disk is still forming stars, Zhúlóng’s overall star formation rate is relatively low, at the level of 66 solar masses per year.
The baryon-to-star conversion efficiency is calculated to be about 0.3, which is about 1.5 times higher than the most efficient galaxies of later epochs. These results suggest that Zhúlóng is forming stars very efficiently and is in the transition stage from star formation to quiescence.
In conclusion, the paper’s authors state that Zhúlóng appears to be the most distant spiral galaxy ever discovered. The properties of this galaxy seem to suggest that mature galaxies emerged much earlier than expected, in the first billion years after the Big Bang.
Further information: Mengyuan Xiao et al., Panoramic: Discovery of a supermassive grand design spiral galaxy in $z\sim5.2$, arXiv (2024). DOI: 10.48550/arxiv.2412.13264
Magazine information: arXiv
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Citation: Astronomers discover supermassive grand design spiral galaxy (December 28, 2024) from https://phys.org/news/2024-12-astronomers-ultra-massive-grand-spiral.html 2024.12 Retrieved on 30th of month
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