Quasars provide some of the most spectacular light shows in the universe. However, they are typically exceedingly rare since they are caused by massive astrophysical forces that don’t happen very often. So it came as quite a surprise when scientists found a group of 11 of them hanging on in the same general area, in what appeared to be equivalent to the galactic countryside. A new paper from Yongming Liang and their co-authors at the University of Tokyo and the National Astronomical Observatory of Japan describes this finding, which they dubbed the Cosmic Himalayas, and some of the weird astronomical circumstances that place the discovery in context.
Quasars are formed when large amounts of matter fall into a supermassive black hole - typically one at the center of a galaxy. That doesn’t happen often, but galaxy collisions where large amounts of matter are running into each other is one such instance where they can form. However, that was much more common in the early universe, so quasars close to use in time are a relative rarity.
So imagine the surprise of the researchers when they found 11 of these supermassive lighthouses within a few megaparsecs of each other. That might sound like a far distance, but ultimately it's a relative eye-blink in universal terms. That being said, they are still the equivalent of 10.5 billion years old, though that is much newer than many other quasars that formed in the early universe.
Fraser discusses what a quasar is and how they form.The researchers collected data on them using the Sloan Digital Sky Survey, and in particular were looking at one part of the universe where there are two distinct galactic “nodes” (i.e. an area with a high density of galaxies) that have very different characteristics. “Node-A”, as it’s called in the paper, is “more mature”, which means it contains brighter Lyman-alpha emitters, a type of young, low-mass galaxy. Whereas, Node-B contains more “blobs”, which are typically associated with a gas build up indicative of the early stages of star formation.
It wasn’t just about the quasars and the galactic nodes though - the intergalactic medium (IGM) played an important part in the study as well. Data was collected using the GALEX satellite and then used to analyze active galactic nuclei, which can be easily obscured by the IGM. That obfuscation was obvious in the data, but only on one side of the “Cosmis Himalayas” - hence the name. Node-A’s IGM was noticeably more transparent than Node-B’s, which was much more opaque. The authors thought that this split was similar to how the Himalayas affected cloud cover on Earth, with a noticeable difference between one side of the mountain range and the other.
Perhaps even more interestingly, the group of quasars didn’t actually fit into either node of dense galaxies - they were about equi-distant to each, with a separation of about 25 million parsecs. That places them square in the intergalactic boondocks, with not enough mass around either of them to warrant the sheer number of quasars that had formed - which was more than double the previous discovery is so small a space.
Fraser discusses where we believe the first quasars came from.Such a mystery requires explanation, and the researcher put forth two of them, pending more research and data collection of course. First, there could be active galaxies that are obscured by the IGM in the general area, making it so that we can’t see these potential sources of these quasars. But a more intriguing answer is that Node-A and Node-B could be colliding, and the rampant quasar formation could be the equivalent of their interface, where massive amounts of matter are coming together between these two dense sections of the universe.
No matter the explanation, finding this many quasars so close to each other is a welcome surprise. It will allow scientists to probe more deeply into how they formed, and what the evolution of some of the most massive structures in the universe actually looks like. All that’s needed is, of course, some more funding, and some more telescope time.
Learn More:
National Astronomical Observatory of Japan - Newly discovered 'Cosmic Himalayas' quasar cluster defies explanation
UT - This New Map of 1.3 Million Quasars Is A Powerful Tool
UT - 860 Million-Year-Old Quasar Had Already Amassed 1.4 Billion Times the Mass of the Sun
UT - Hubble Sees Two Quasars Side by Side in the Early Universe