An Early Circular Galaxy

[Recusant]

Well, roughly circular, or course. Nearly 11 billion light years from here, so the collision event that is believed to have blown a hole through the center of what was likely an elliptical galaxy occurred rather early in the development of the Universe.

"Astronomers see 'cosmic ring of fire', 11 billion years ago" | Science in Public

An artist's impression of the ring galaxy.
Image Credit: James Josephides, Swinburne Astronomy Productions

Astronomers have captured an image of a super-rare type of galaxy – described as a "cosmic ring of fire" – as it existed 11 billion years ago.

The galaxy, which has roughly the mass of the Milky Way, is circular with a hole in the middle, rather like a titanic doughnut. Its discovery, announced in the journal Nature Astronomy, is set to shake up theories about the earliest formation of galactic structures and how they evolve.

"It is a very curious object that we've never seen before," said lead researcher Dr Tiantian Yuan, from Australia's ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D). "It looks strange and familiar at the same time."

The galaxy, named R5519, is 11 billion light-years from the Solar System. The hole at its centre is truly massive, with a diameter two billion times longer than the distance between the Earth and the Sun. To put it another way, it is three million times bigger than the diameter of the supermassive black hole in the galaxy Messier 87, which in 2019 became the first ever to be directly imaged.

"It is making stars at a rate 50 times greater than the Milky Way," said Dr Yuan, who is an ASTRO 3D Fellow based at the Centre for Astrophysics and Supercomputing at Swinburne University of Technology, in the state of Victoria.

"Most of that activity is taking place on its ring – so it truly is a ring of fire."

Working with colleagues from around Australia, US, Canada, Belgium and Denmark, Dr Yuan used spectroscopic data gathered by the WM Keck Observatory in Hawaii and images recorded by NASA's Hubble Space Telescope to identify the unusual structure.

The evidence suggests it is a type known as a "collisional ring galaxy", making it the first one ever located in the early Universe.

[Continues . . .]

A PDF of the paper is available here:

"A giant galaxy in the young universe with a massive ring" | Nature Astronomy

Abstract:

In the local (z ⇠ 0) universe, collisional ring galaxies make up only ⇠0.01% of galaxies and are formed by head-on galactic collisions that trigger radially propagating density waves. These striking systems provide key snapshots for dissecting galactic disks and are studied extensively in the local universe. However, not much is known about distant (z > 0.1) collisional rings. Here we present
a detailed study of a ring galaxy at a look-back time of 10.8 Gyr (z = 2.19). Compared with our Milky Way, this galaxy has a similar stellar mass, but is 1.5-2.2⇥ larger in stellar half-light radius and is forming stars 50⇥ faster. The large diffuse stellar light outside of the star-forming ring, combined with a radial velocity on the ring and an intruder galaxy nearby, provides evidence for this galaxy being the most distant collisional ring confirmed to date. If the ring is secularly evolved, the implied large bar in a giant disk would be inconsistent with the current understanding of the earliest formation of barred spirals. Contrary to previous predictions, this work suggests that massive collisional rings are as rare 11 Gyr ago as they are today. Our discovery offers a unique pathway for studying density waves in young galaxies, as well as constraining the cosmic evolution of spiral disks and galaxy groups.

[Randy]

This is the sort of thing that captivates me. It's a good find.

[Tank]

Fantastic

[Dark Lightning]

"Smoke Rings" made of stars! That's awesome!