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Home / Science / Global simulations show that the Webb telescope can detect distant galaxies hidden in the glare of Quasars

Global simulations show that the Webb telescope can detect distant galaxies hidden in the glare of Quasars



High-redshift quasar and associated galaxy

This artist’s illustration depicts two galaxies that existed in the first billions of years of the universe. In the larger galaxy on the left in the center is a brilliant quasar, the glow of which is provided by the hot matter surrounding the supermassive black hole. Scientists have estimated that the resolution and infrared sensitivity of the future James Webb Space Telescope will allow him to detect such a dusty galaxy, despite the beam of the quasar spotlight. Credit: J. Olmsted (STScI)

Webb’s observations will search for dust galaxies of the first billion years of the universe.

The brightest objects in the distant, young universe are quasars. These space beacons feed on supermassive black holes that waste material. Quasars are so bright that they can overshadow their entire host galaxy, making it difficult to study these galaxies and compare them to galaxies without quasars.

A new theoretical study explores how well NASAin future James Webb Space Telescope, scheduled for launch in 2021, will be able to separate the light of the host galaxies from the bright central quasar. Researchers have found that Webb could detect galaxies that existed only 1 billion years after the Big Bang.


This video enhances a large-scale modeling of the universe called BlueTides. Like the iconic Powers of Ten video, each step is 10 times shorter than the previous one. The first frame covers about 200 million light-years, while the fourth and last frame covers only 200,000 light-years and contains two galaxies. The researchers used this simulation to study the properties of galaxies containing quasars, bright galactic nuclei that feed by building supermassive black holes. Credit: Y. No (Carnegie Mellon University) and L. Hustak (STScI)

Quasars are the brightest objects in the universe and among the most energetic. They eclipse entire galaxies of billions of stars. Supermassive black hole underlies every quasar, but not every black hole is a quasar. Only black holes, which feed most greedily, can feed a quasar. The material that enters the supermassive black hole heats up and causes the quasar to glow in the universe like a lighthouse beacon.

Although quasars are known to live in the centers of galaxies, it was difficult to say what they are and how they compare to galaxies without quasars. The problem is that quasar reflections make it difficult or impossible to emit light from the surrounding host galaxy. It’s like looking straight into a car’s headlight and trying to figure out which car it’s attached to.

New study[1] suggests that NASA’s James Webb Space Telescope, due to be launched in 2021, will be able to detect galaxies of some distant quasars, despite their small size and obscuring dust.

Simulated infrared images from Webb and Hubble

These simulations show what the quasar and its host galaxy will look like on future James Webb Space Telescopes (top) and Hubble Space Telescopes (bottom) at 1.5 and 1.6 μm infrared wavelengths, respectively. The larger Webb mirror will provide more than 4 times the resolution, allowing astronomers to separate the light from the galaxy from the predominant light from the central quasar. Individual images cover about 2 arcseconds in the sky, representing a distance of 36,000 light-years at a redshift of 7. Credit: M. Marshall (University of Melbourne)

“We want to know in which galaxies these quasars live. This can help us answer questions like: How can black holes grow so fast? Is there a relationship between the mass of the galaxy and the mass of the black hole, as we see in the neighboring universe? “said lead author Madeleine Marshall of the University of Melbourne in Australia, who has worked at the ARC Center of Excellence in All Astrophysics of the Sky in 3 Dimensions.

Answering these questions is difficult for a number of reasons. In particular, the more distant the galaxy, the more its light is stretched to longer waves due to the expansion of the universe. As a result, ultraviolet light from the accretion disk of a black hole or young stars in the galaxy transitions to infrared wavelengths.

In a recent study[2], astronomers have used closer to NASA’s infrared capabilities Hubble Space Telescope to study known quasars in the hope of detecting the surrounding glow of host galaxies without significant discoveries. This suggests that the dust in galaxies obscures the light of their stars. Webb’s infrared detectors can peek through the dust and reveal hidden galaxies.

“Hubble just doesn’t go far enough into infrared light to see the host galaxies. Here, Webb will really excel, ”said Rogir Windhorst of the University of Arizona at Tempe, co-author of the Hubble study.

To determine what they expected to see Webb, the team used a state-of-the-art computer simulation called BlueTides, developed by a team led by Titian Di Matteo of Carnegie Mellon University in Pittsburgh, Pennsylvania.

“BlueTides is designed to study the formation and evolution of galaxies and quasars over the first billions of years of the universe’s history. Its large space volume and high spatial resolution allow us to study these rare Khazar quasars on a statistical basis, ”said Yuain Ni of Carnegie Mellon University, who led the BlueTides simulation. BlueTides agrees well with current observations and allows astronomers to predict what Webb should see.

The team found that galaxies containing quasars were generally smaller than the average, only about 1/30 of the diameter Milky Way despite the fact that it contains almost as much mass as our galaxy. “The host galaxies are surprisingly tiny compared to the average galaxy at the time,” Marshall said.

The modeling galaxies also typically formed stars rapidly, up to 600 times faster than the current rate of star formation in the Milky Way. “We have found that these systems are growing very fast. They look like precocious children – they do everything early, ”explained co-author Di Matteo.

The team then used these simulations to determine what Webb’s cameras would see if the observatory studied these remote systems. They found that it would be possible to distinguish the host galaxy from the quasar, although it is still difficult due to the small size of the galaxy in the sky.

“For the first time, Webb will be able to observe these very distant host galaxies,” Marshall said.

They also considered what Webb spectrographs could derive from these systems. Spectral studies that separate incoming light into component colors or wavelengths will be able to detect the chemical composition of dust in these systems. Finding out how many heavy elements they contain can help astronomers understand their history of star formation, as most chemical elements are produced in stars.

Webb could also determine whether or not isolated host galaxies. Hubble’s research showed that satellite quaternary galaxies were found in most quasars, but it was not possible to determine whether these galaxies were actually nearby or whether they were random superpositions. Webb’s spectral capabilities will allow astronomers to measure redshifts and, consequently, the distances of those obvious satellite galaxies to determine if they are at the same distance as a quasar.

Finally, Webb’s observations should give new insights into these extreme systems. Astronomers are still trying to figure out how a black hole can grow a billion times more in weight than our Sun in just a billion years. “These big black holes shouldn’t exist so early because they didn’t have enough time to grow so massive,” said co-author Stuart White of the University of Melbourne.

Further studies of quasars will also be fueled by synergies between several future observatories. Infrared research with the Euclid mission of the European Space Agency, as well as the Ground Observatory. Both observatories will significantly increase the number of known distant quasars. These newly formed quasars will then be studied by Hubble and Webb to gain new insights into the years of the universe’s existence.

List of references:

  1. “Host galaxies z = 7 quasars: predictions from BlueTides modeling”, Madeleine A Marshall, Yuain No, Titian Di Matteo, J. Stewart B. White, Stephen Wilkins, Rupert AK Croft and Jussy K. Kuusisto, October 5, 2020 ., Monthly reports of the Royal Astronomical Society.
    DOI: 10.1093 / mnras / staa2982
  2. “Limitation of ultraviolet radiation at rest from the far-infrared light of 6 quasar hosts” MA Marshall, M. Mechtli, RA Windhorst, SH Cohen, RA Yansen, L. Jiang, W. R. Jones, JSB Wyithe1, X. Fana. , N.P. Hutty, K. Janke, WC Kiel, A. M. Kekemoer, W. Marian, K. Wren, J. Robinson, H.A. Rettgering, R.E. Jan, August 27, 2020, Astrophysical Journal.
    DOI: 10.3847 / 1538-4357 / abaa4c

The modeling of Bluetides (project PI: Tiziana Di Matteo from Carnegie Mellon University) was performed on a computing device with a stable blue Waters petascal, supported by the National Science Foundation.

The James Webb Space Telescope will be the world’s first space science observatory when it opens in 2021. Webb will solve mysteries in our solar system, look into distant worlds around other stars and explore the mysterious structures and origins of our universe and our place in it. Webb is an international program run by NASA and its partners, ESA (European Space Agency) and the Canadian Space Agency.




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