In fall of 2019, astronomers with The Cosmic Dawn Center (DAWN) at the Niels Bohr Institute, discovered an ancient cluster of galaxies at the dawn of the cosmos, the most distant ever found at 13.0 billion light years away, suggesting that the “the dark skeleton of the universe” existed at a time when the cosmos was only about 800 million years old or 6 percent of its present age.
But these ancient clusters make up only a minute fraction of what actually exist. Astronomers have concluded that the volume of space-time within range of our telescopes—‘the universe’—is only a tiny fraction of the aftermath of the big bang. “We’d expect far more galaxies located beyond the horizon, unobservable,” says the renowned astrophysicist, Martin Rees, “each of which (along with any civilizations it hosts) will evolve rather like our own.”
The Dark Skeleton
In the universe we see today, there are clusters of galaxies that encompass hundreds of member galaxies including tens of massive galaxies. These massive clusters are the largest astronomical objects in the universe making up a huge network of galaxies that form the “large-scale structure” –the dark skeleton–of the universe.How these clusters of galaxies formed and evolved through the 13,8 billion years long history of the universe has been an enduring mystery.
The Phoenix Cluster
In an important result for understanding the coevolution of galaxies, gas, and black holes in galaxy clusters, radio astronomers at the National Astronomical Observatory of Japan (NAO) have detected jets of hot gas blasted out by a black hole in the galaxy at the heart of the Phoenix Galaxy Cluster, located 5.9 billion light-years away in the constellation Phoenix. The object was was detected by X-ray observations. of very dilute gas that pervades throughout a cluster.
If this intra-cluster gas cooled, the NAOJreports” it would condense under its own gravity to form stars at the center of the cluster. However, cooled gas and stars are not usually observed in the hearts of nearby clusters, indicating that some mechanism must be heating the intra-cluster gas and preventing star formation. One potential candidate for the heat source is jets of high-speed gas accelerated by a super-massive black hole in the central galaxy.”
The Phoenix Cluster raises the question “does the central galaxy have black hole jets as well” because it is unusual in that it does show signs of dense cooled gas and massive star formation around the central galaxy.
The composite image above shows powerful radio jets from the supermassive black hole at the center of a galaxy in the Phoenix Cluster inflating huge ‘bubbles’ in the hot, ionized gas surrounding the galaxy (the cavities inside the blue region imaged by NASA’s Chandra X-ray observatory). Hugging the outside of these bubbles, ALMA discovered an unexpected trove of cold gas, the fuel for star formation (red). The background image is from the NASA/ESA Hubble Space Telescope.)ALMA / ESO / NAOJ / NRAO / NASA / ESA / Hubble / CXC / MIT / H. Russell et al / M. McDonald et al / B. Saxton)
Search for Black Hole Jets
The NAO team led by Takaya Akahori used the Australia Telescope Compact Array (ATCA) to search for black hole jets in the Phoenix Cluster with the highest resolution to date. They have announced that they detected matching structures extending out from opposite sides of the central galaxy. Comparing with observations of the region taken from the Chandra X-ray Observatory archive data shows that the structures detected by ATCA correspond to cavities of less dense gas, indicating that they are a pair of bipolar jets emitted by a black hole in the galaxy. Therefore, the team discovered the first example, in which intra-cluster gas cooling and black hole jets coexist, in the distant Universe.
Further details of the galaxy and jets could be elucidated through higher-resolution observations with next generation observational facilities, such as the Square Kilometre Array scheduled to start observations in the late 2020s.
The Daily Galaxy, Max Goldberg, via University of Tokyo
Hubble Image at the top of the page: was made by combining data from Chandra, Hubble and the VLA. X-rays from Chandra depict hot gas in purple and radio emission from the VLA features jets in red. Optical light data from Hubble show galaxies (in yellow), and filaments of cooler gas where stars are forming (in light blue).