Astronomers have used the Dark Energy Camera's wide-field view to confirm that quasars powered by supermassive black holes in the early universe were clustered in dense neighborhoods. However, it seems these cosmic beasts weren't exactly the best neighbors.
The team behind this research discovered that quasars are “noisy neighbors” that emit radiation that can cut off star formationthus “killing” the galaxies that live in their nearby cosmic neighborhoods. As a result, the closest companion galaxies around some quasars do not grow and are therefore too small and faint to be seen.
The team says these results on the “urban density” of quasars and their companion galaxies could also explain why some previous studies of the density of the early Universe have shown tightly packed galaxies and quasars, while others have indicated a lack of companion galaxies around quasars.
To carry out their study, the researchers focused on the quasar VIK 2348-3054, located about 12.8 light years from Earth. The distance to this quasar is very well defined thanks to the Great Millimeter Set of Atacama (SOUL).
With its target selected, the Dark Energy Camera, or DECam, mounted on the Victor M. Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory in Chile, allowed the team to conduct the largest area-of-sky search ever conducted in a quasar of the early universeWhile DECam's three-square-degree field of view provided an expansive overview of VIK 2348–3054's cosmic neighborhood, its narrowband filter was the perfect complement to allowing the team to focus on The companion galaxies surrounding the quasar.
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“This quasar study really was the perfect storm,” said team leader Trystan Lambert, a postdoctoral researcher at the University of Western Australia node. from the International Centre for Radio Astronomy Research (ICRAR), said in a statement“We had a quasar with a well-known distance, and DECam on the Blanco telescope offered the huge field of view and exact filtering we needed.”
The first quasars had well-stocked pantries
Quasars are among the brightest sources of light in the known universe, often outshining the combined light of all the stars in galaxies. that surrounds them. The engine that drives these emissions is central supermassive black holes with masses millions of times greater than that of the Sun.
Like any engine, these cosmic monsters need fuel. In the case of quasars, this fuel comes in the form of gas and dust that orbit the respective black holes, called “quasars.”accretion diskwhich gradually feeds into the voids. The tremendous gravitational influence of the black hole causes an enormous amount of friction in the accretion disk, superheating this material and creating plasma and intense electromagnetic radiation that forms the quasar's emissions.
Black holes are messy eatersHowever, some of the material is channeled by powerful magnetic fields towards its poles, where it is accelerated to near-light speeds and ejected in collimated jets of plasma. These jets are also accompanied by bright electromagnetic emissions.
To facilitate their powerful emissions and allow their supermassive black holes to grow to enormous sizes in the relatively early universe, quasars must be surrounded by an abundance of material on which to feed.
The necessarily high feeding rate has led many astronomers to propose that quasars must be located in some of the densest regions of the universe where there is plenty of gas available. However, observations have not always supported that idea.
To investigate this, Lambert and his colleagues counted the companion galaxies around VIK J2348-3054 by measuring a specific emission called Lyman-alpha radiationThis is the sign of a form of hydrogen that has had its electrons stripped at high temperatures. The electrons and hydrogen nuclei recombine and the previously ionized hydrogen atoms regain some electrons. This is a typical indicator of star formation and therefore indicates that younger and smaller galaxies are giving rise to stellar bodies.
Fortunately, Lyman-alpha radiation is a good determinant of red shift values, The change in the frequency of light that we detect when a light source moves away from our observation point in the universe. This means that it serves as a good way to determine the distances to these small, young galaxies. These measurements can then be used to build a three-dimensional model of the region around a quasar.
Doing the same for the quasar VIK J2348-3054, the team found 38 companion galaxies, up to 60 million light-years away, indicating a dense region of space. To the surprise of Lambert and his colleagues, they also found a complete absence of companion galaxies within 15 million light-years of the quasar.
That could explain why previous research investigating the environments of quasars has yielded conflicting results about density. That’s because research indicating empty space around quasars might have focused on the immediate regions around these supermassive black holes. Those regions would have been populated by the undetectable galaxies that had quenched star formation. In contrast, research showing crowded regions of space around quasars looked at the big picture, but didn’t focus on the immediate vicinity around quasars. DECam provided a clearer picture because it facilitated the only study so far that included data from large areas to small areas.
“DECam's extremely wide view is necessary to study quasar neighborhoods in depth. You really have to open up to a larger area,” Lambert said. “This suggests a reasonable explanation for why previous observations are in conflict with each other.”
Researchers suspect they know the reason for the apparent scarcity of companion galaxies in the vicinity of this quasar. They suggest it could be the result of Intense radiation from the quasar This prevents star formation and therefore kills the growth of nearby galaxies. That means those galaxies are probably there, but they are too small and faint to see.
“Some quasars are not quiet neighbors,” Lambert concluded. “Stars in galaxies form from gas that is cold enough to collapse under its own gravity. Luminous quasars can potentially be so bright that they illuminate this gas in nearby galaxies and heat it up, preventing this collapse.”
The team's research appears in the journal Astronomy and Astrophysics.
