Astronomers discover far-off galaxies using neural networks

It’s similar to how paleontologists use certain known fossils Indexed Fossil Until assessing rock formations and ancient environments so far, astronomers look for specific patterns of light emissions from space to mark the age of space history. For example, early galaxies give the UV rays that originate from electrons in hydrogen atoms to the type of ultraviolet rays that exert from the second lowest to the lowest energy state. Lyman Alpha or ly⍺ Emission.

For decades, astronomers have associated ly⍺ emissions with periods within billions of years of a big bang called the Big Bang. The era of reionizationwhen the average speed of star formation in galaxies was much higher than today. When they find a galaxy that emits light strongly, they classify it into ly⍺Emitter or Lae And we can be sure that it goes back to the era of reionization. Observing Laes, astronomers talk more about the history of the Milky Way and other galaxies like us.

However, researchers face confounding factors when looking for Laes. The expansion of the universe distorts light in a process called Cosmological redshift. However, more prominently Dustboth Intergalacticcovers the light. While astronomers can analyze the full light of light from the galaxy to find evidence of ly⍺ emissions, it would be much faster to develop tools to predict whether a galaxy is likely to be a LAE based on more readily available measurements.

One team of astronomers developed a model for this problem only Machine Learning A technique known as a Neural Networks. This technique replicates how neurons in the brain function, with several interconnected layers receiving and transmitting signals based on initial inputs and generating final outputs.. The trick is that the programmer knows what inputs to input and what output they expect in the end. The algorithm itself needs to know how best to set up a central connection, what to look for, and how to rank the importance of each input.

The team began with data from two surveys of light sources in space: 926 galaxies VanderOf these, only 520 are laes, starting from 507 Musethey were all laes. They trained the algorithm using 80% of this data to explicitly communicate which sources are actual LAES and which sources are not. They saved the remaining 20% ​​of the data for testing.

Through this initial test, the team identified six parameters of neural networks to focus on evaluating galaxies for LAE potential. These parameters were the rate of star formation, total star mass, UV brightness, UV emission patterns, age, and dust. They programmed the network to output an estimate of the probability that a particular galaxy is a LAE, and thought that what was above 70% meant that the algorithm classified it as an LAE.

When we created a neural network using training data, the team tested several additional rounds. Using early test data, their networks found that they correctly identified the network in 77% of the time, as there was only a 14% chance of false positives. When they looked at what their network prioritized to make these predictions, they found that the most important factors were the galaxy’s UV emission pattern, its UV brightness, and the mass of its star.

Following this initial success, the team applied the network to another investigation. cosmos2020and a subset of that raise, SC4Kwith fewer details than the training data survey. From these datasets, the team’s neural network identified true Laes for 72% of the time.

The team’s final results came when they applied neural networks to data from NASA’s new telescope. jwst. The ultimate goal in their model is to study the distant past of the universe, and JWST aims to see better-looking sources than ever before, so the success of the test is Already checking the results of LAE from JWST It will be a good sign of future success. They found a true positive rate of 91% in JWST data, showing the validity of their approach and illuminated the path to know more about the history of the universe.


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Source: sciworthy.com

Astronomers find previously unknown quasar in far-off galaxy cluster

Astronomers used NASA’s Chandra X-ray Observatory and NSF’s Carl G. Jansky Very Large Array (VLA) to locate H1821+643, the closest quasar hosted by a galaxy cluster, about 3.4 billion light years away. The quasar was found to be more powerful than many supermassive black holes in other galaxy clusters.



This composite image shows quasar H1821+643.Image credit: NASA / CXC / University of Nottingham / Russell other. / NSF / NRAO / VLA / SAO / N. Walk.

Quasars are a rare and extreme class of supermassive black holes that violently pull matter inward, producing intense radiation and sometimes powerful jets.

This quasar, known as H1821+643, is about 3.4 billion light-years from Earth and contains a black hole with a mass of 4 billion solar masses.

Most growing supermassive black holes pull matter in at a slower rate than quasars.

Astronomers have been studying the effects of these more common black holes by observing black holes at the centers of galaxy clusters.

Periodic explosions from such black holes prevent the massive amount of superheated gas embedded in the black hole from cooling down, increasing the number of stars forming in its host galaxy and the fuel pouring toward the black hole. limit the amount of

Little is known about how much influence quasars within galaxy clusters have on their surroundings.

“Our research shows that quasars appear to have given up much of the control imposed by slower-growing black holes. The appetite of black holes is unmatched in their influence,” Nottingham said. University astronomer Dr Helen Russell said.

To reach this conclusion, Russell and his colleagues used Chandra to study the hot gas surrounding H1821+643 and its host galaxy.

But the bright X-rays from quasars have made it difficult to study the weaker X-rays from hot gases.

“To reveal the effects of a black hole, we had to carefully remove the X-ray glare. Then we found that it actually had little effect on its surroundings,” says Harvard University. said Dr. Paul Nalsen, an astronomer at the Smithsonian Center for Astrophysics.

Using Chandra, astronomers discovered that the density of gas near the black hole at the center of a galaxy is much higher than in more distant regions, and the temperature of the gas is much cooler.

Researchers believe that when there is little or no energy input (usually from an explosion from a black hole), hot gas behaves this way to prevent it from cooling and flowing toward the center of the cluster. Expect.

“The supermassive black hole generates far less heat than other black holes at the center of galaxy clusters. This allows the hot gas to cool rapidly and form new stars, which fuel the black hole. It also acts as a source,” said Dr Lucy Crews, an astronomer at the Open University.

The researchers determined that the equivalent of about 3,000 solar masses per year of hot gas has cooled to the point where it is no longer visible in X-rays.

This rapid cooling easily supplies enough material for the 120 solar masses of new stars observed to form each year within the host galaxy and the 40 solar masses consumed by black holes each year. be able to.

The scientists also investigated the possibility that radiation from quasars directly causes cooling of the cluster's hot gases.

This involves photons of light from the quasar colliding with electrons in the hot gas, increasing the energy of the photons and causing the electrons to lose energy and cool down.

This study showed that this type of cooling is probably occurring within the cluster containing H1821+643, but is too weak to explain the large amount of gas cooling seen.

Dr Thomas Braben, an astronomer at the University of Nottingham, said: “This black hole may not be producing enough because it isn't pumping any heat into its surroundings, but the current situation won't last forever.'' ” he said.

“Ultimately, the rapid uptake of fuel by the black hole should increase the jet's power and strongly heat the gas.”

“After that, the growth of the black hole and its galaxy should slow down significantly.”

team's paper will be published in Royal Astronomical Society Monthly Notices.

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HR Russell other. 2024. Cooling flow around low-redshift quasar H1821+643. MNRAS, in press. arXiv: 2401.03022

Source: www.sci.news

Scientists observe massive outburst from supermassive black hole in far-off galaxy cluster

Some of the gas erupts from the supermassive black hole located at the center of galaxy cluster SDSS J1531+3414 (abbreviated SDSS J1531) until it reaches a temperature high enough to form numerous star clusters. Cooled down.

Multi-wavelength image of the massive galaxy cluster SDSS J1531+3414.Image credits: NASA / CXC / SAO / Omorui other. / STScI / Tremblay other. / Astron / Loafers / NASA / CXC / SAO / N. Walk.

SDSS J1531 is a huge galaxy cluster containing hundreds of individual galaxies and a huge reservoir of hot gas and dark matter.

At the center of SDSS J1531, two of the cluster's largest galaxies collide with each other.

Surrounding these merging giants are 19 large star clusters called superclusters, arranged in an “S” shape similar to beads on a string.

Dr. Osase Omoruyi and colleagues at Harvard University and the Smithsonian Center for Astrophysics are using NASA's Chandra X-ray Observatory, the LOFAR radio network, and other telescopes to discover how this chain of unusual star clusters formed. I found out what happened.

The discovery of evidence of an ancient mega-eruption in SDSS J1531 provided important clues.

The eruption may have occurred when a supermassive black hole at the center of one of the large galaxies produced a very powerful jet.

As the jet traveled through space, it pulled surrounding hot gas away from the black hole, creating a huge cavity.

“We're already observing this system as it existed 4 billion years ago, when the Earth was just forming,” Omoruyi said.

“This ancient cavity is a fossil of the black hole's influence on its host galaxy and its surroundings, and tells us about important events that occurred almost 200 million years ago in the history of this star cluster.”

Evidence for the cavity comes from bright X-ray emission “wings” seen on Chandra that track dense gas near the center of SDSS J1531.

These wings form the edges of the cavity, and the less dense gas between them is part of the cavity.

LOFAR shows radio waves from the remains of the jet's energetic particles filling a huge cavity.

Taken together, these data provide convincing evidence for an ancient great explosion.

Astronomers also discovered cold and warm gas near the cavity's opening, detected by the Atacama Large Millimeter and Submillimeter Array (ALMA) and Gemini North Telescope, respectively.

They argue that some of the hot gas pushed out of the black hole eventually cooled down to cold, warm gas.

They believe that the tidal effects of the two galaxies merging compressed the gas along a curved path, forming the star cluster in a “string-bead” pattern.

“We reconstructed the sequence of events that may have occurred within this cluster over a wide range of distances and times,” said Dr. Grant Tremblay, also of Harvard University and the Smithsonian Center for Astrophysics.

“It started when a black hole, just one light-year in diameter, formed a cavity about 500,000 light-years wide.”

“This single event triggered the formation of young star clusters almost 200 million years later, each several thousand light-years in diameter.”

Although the authors only looked at the radio waves and cavity from one jet, black holes typically fire two jets in opposite directions.

They also observed radio emissions further out from the galaxy that could be the remains of a second jet, but it was unrelated to the detected cavity.

They speculate that radio and X-ray signals from other eruptions may have diminished to the point where they could no longer be detected.

“We believe the evidence for this large-scale eruption is strong, but further observations from Chandra and LOFAR will confirm the case,” Dr. Omoruyi said.

“We hope to learn more about the origins of the cavities we have already detected and find the cavities we expect to find on the other side of the black hole.”

a paper Regarding the survey results, astrophysical journal.

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Omase Omorui other. 2024. A “string bead” star formation associated with one of the most powerful she-AGN outbursts observed in the Cool Core Galaxy Cluster. APJ, in press. arXiv: 2312.06762

Source: www.sci.news