Double or nothing—astronomers rethink quasar environment

"Luminous Quasars Do Not Live in the Most Overdense Regions of Galaxies at z~4",
Galaxy distribution and close-ups of some protoclusters revealed by HSC. Higher- and lower-density regions are represented by redder and bluer colors, respectively. In the close-ups, white circles indicate the positions of distant galaxies. The red regions are expected to evolve into galaxy clusters. From the close-ups, we can see various morphologies of the overdense regions: some have another neighboring overdense region, or are elongated like a filament, while there are also isolated overdense regions. Credit: NAOJ

Using Hyper Suprime-Cam (HSC) mounted on the Subaru Telescope, astronomers have identified nearly 200 "protoclusters," the progenitors of galaxy clusters, in the early universe, about 12 billion years ago, about ten times more than previously known. They also found that quasars don't tend to reside in protoclusters; but if there is one quasar in a protocluster, there is likely a second nearby. This result raises doubts about the relation between protoclusters and quasars.

In the , are not distributed uniformly. There are some places, known as clusters, where dozens or hundreds of galaxies are found close together. Other galaxies are isolated. To determine how and why clusters formed, it is critical to investigate not only mature as seen in the present universe but also observe protoclusters, galaxy clusters in the process of forming.

Because the speed of light is finite, observing distant objects allows us to look back in time. For example, the light from an object 1 billion light-years away was actually emitted 1 billion years ago and has spent the time since then traveling through space to reach us. By observing this light, astronomers can see an image of how the universe looked when that light was emitted.

Even when observing the distant (early) universe, protoclusters are rare and difficult to discover. Only about 20 were previously known. Because distant protoclusters are difficult to observe directly, are sometimes used as a proxy. When a large volume of gas falls towards the super in the center of a galaxy, it collides with other gas and is heated to extreme temperatures. This hot gas shines brightly and is known as a quasar. The thought was that when many galaxies are close together, a merger, two galaxies colliding and melding together, would create instabilities and cause gas to fall into the super massive black hole in one of the galaxies, creating a quasar. However, this relationship was not confirmed observationally due to the rarity of both quasars and protoclusters.

In order to understand protoclusters in the distant universe a larger observational sample was needed. A team including astronomers from the National Astronomical Observatory of Japan, the University of Tokyo, the Graduate University for Advanced Studies, and other institutes is now conducting an unprecedented wide-field systematic survey of protoclusters using the Subaru Telescope's very wide-field camera, Hyper Suprime-Cam (HSC). By analyzing the data from this survey, the team has already identified nearly 200 regions where galaxies are gathering together to form protoclusters in the 12 billion years ago.

Double or nothing: Astronomers rethink quasar environment
Stars indicate quasars and bright (faint) galaxies at the same epoch are shown as circles (dots). The galaxy overdensity with respect to the average density is shown by the contour. The pair members are associated with high density regions of galaxies. Credit: NAOJ

The team also addressed the relationship between protoclusters and quasars. The team sampled 151 luminous quasars at the same epoch as the HSC protoclusters and to their surprise found that most of those quasars are not close to the overdense regions of galaxies. In fact, their most luminous quasars even avoid the densest regions of galaxies. These results suggest that quasars are not a good proxy for protoclusters and more importantly, mechanisms other than galactic mergers may be needed to explain quasar activity. Furthermore, since they did not find many galaxies near the brightest quasars, that could mean that hard radiation from a quasar suppresses galaxy formation in its vicinity.

On the other hand, the team found two "pairs" of quasars residing in protoclusters. Quasars are rare and pairs of them are even rarer. The fact that both pairs were associated with protoclusters suggests that quasar activity is perhaps synchronous in protocluster environments. "We have succeeded in discovering a number of protoclusters in the for the first time and have witnessed the diversity of the quasar environments thanks to our wide-and-deep observations with HSC," says the team's leader Nobunari Kashikawa (NAOJ).

"HSC observations have enabled us to systematically study protoclusters for the first time." says Jun Toshikawa, lead author of the a paper reporting the discovery of the HSC protoclusters, "The HSC protoclusters will steadily increase as the survey proceeds. Thousands of protoclusters located 12 billion light-years away will be found by the time the observations finish. With those new observations we will clarify the growth history of protoclusters."

Explore further

Subaru telescope discovers the most distant protocluster of galaxies

More information: Jun Toshikawa et al. GOLDRUSH. III. A systematic search for protoclusters at z ∼ 4 based on the >100 deg2 area, Publications of the Astronomical Society of Japan (2017). DOI: 10.1093/pasj/psx102

Hisakazu Uchiyama et al. Luminous quasars do not live in the most overdense regions of galaxies at z ∼ 4, Publications of the Astronomical Society of Japan (2017). DOI: 10.1093/pasj/psx112

Masafusa Onoue et al. Enhancement of galaxy overdensity around quasar pairs at z < 3.6 based on the Hyper Suprime-Cam Subaru Strategic Program Survey, Publications of the Astronomical Society of Japan (2017). DOI: 10.1093/pasj/psx092

Citation: Double or nothing—astronomers rethink quasar environment (2018, March 13) retrieved 20 August 2019 from
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Mar 13, 2018
"When a large volume of gas falls towards the super massive black hole in the center of a galaxy, it collides with other gas and is heated to extreme temperatures."
In the universe there is no up and down. The same rules apply to the North or South Pole. Gathering = Movement. Why would the "downfall" be an extremely hot process? Why, this is not true for the movement? What heats the gas, in the author, gas furnace?Happy is he who does not think.
So spaceship that goes to the "black hole", becomes hot, 15,000 ly before entering into a black hole? The diameter of the center of the galaxy is ~ 30,000 ly from the north to the south pole.

Mar 13, 2018
In the universe there is no up and down.

But objects can still fall onto more massive objects.

Or, if you're close to an object with enough mass, every direction leads to 'down'.

Mar 13, 2018
Your statement: down = south and north pole, equator and every other point. How, you, distinguish the south and north poles (both are down). What is south and what is north?

Mar 13, 2018
That's interesting. Two ways:

First, why do quasars not show up in very many protoclusters?

Second, why, when they show up in protoclusters, are there two?

Still, the sample size is small so far. As this project continues we should get more data. If these trends keep up, this could be a big clue to galaxy dynamics.

Mar 14, 2018
".. But, when a cyclone, with a diameter of 1000 km or more, makes a turn in a second, the strong forces are created, which by the particles' friction create a light effect. A cyclone is a spiral thread, up to 30 000 of light years in length. The larger the speed of a cyclone, the stronger the friction inside the eye is. Also, the more intensive is the glow and more significant are different kinds of radiation. A visible trace that is related to the released matter is only the thrust of radiation waves from the eye of a cyclone on the gas and matter that exist outside of that event. .." http://www.svemir...html#14b

Mar 15, 2018
First, why do quasars not show up in very many proto-clusters?

Small sample. And it is a matter of enough time to grow sufficiently internally. See a newly forming quasar in my first post.

The growing core seen by Spitzer is dissipating the surrounding galaxy. And daughter galaxies are diverging therefrom. Eventually, all that will left is the bare growing core, a quasar.

Second, why, when they show up in protoclusters, are there two?

Because regions of high mass density provide the sub-quantum fertile conditions for more rapid formation of new matter, growing surrounding stars more rapidly. Hence, more likely a second rapid quasar forms.

Still, the sample size is small so far. As this project continues we should get more data. If these trends keep up, this could be a big clue to galaxy dynamics.

It already has, to those with a bit of logic. Sorry maniacs. You will never win.

Mar 15, 2018
...The ability of black holes to swallow gas is actually quite limited: the faster the gas is falling, the more radiation gets generated in accretion disk, the more gas gets blow out by radiational pressure.

This is an unstable feedback system, leading to a collapse of the very mechanism by which the intellectually challenged merger maniacs cling to as an explanation. Such a system has a very limited lifespan, so that the extremely luminous systems that we actually observe should be at best, very rare. But the maniacs still cling, since they got nothing!

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