From James Webb Space Telescope: “Simulations Show Webb Telescope Can Reveal Distant Galaxies Hidden in Quasars’ Glare”

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NASA Webb Telescope

From James Webb Space Telescope

October 14, 2020

Media Contact:
Christine Pulliam
Space Telescope Science Institute, Baltimore, Maryland

Science Contact:
Madeline Marshall
University of Melbourne, Melbourne, Australia

This artist’s illustration portrays two galaxies that existed in the first billion years of the universe. The larger galaxy at left hosts a brilliant quasar at its center, whose glow is powered by hot matter surrounding a supermassive black hole. Scientists calculate that the resolution and infrared sensitivity of NASA’s upcoming James Webb Space Telescope will allow it to detect a dusty host galaxy like this despite the quasar’s searchlight beam. Credit: J. Olmsted (STScI).

These simulated images show how a quasar and its host galaxy would appear to NASA’s upcoming James Webb Space Telescope (top) and Hubble Space Telescope (bottom) at infrared wavelengths of 1.5 and 1.6 microns, respectively. Webb’s larger mirror will provide more than 4 times the resolution, enabling astronomers to separate the galaxy’s light from the overwhelming light of the central quasar. The individual images span about 2 arcseconds on the sky, which represents a distance of 36,000 light-years at a redshift of 7. Credit: M. Marshall University of Melbourne (AU).

Webb observations will seek dusty galaxies from the first billion years of the universe.

The brightest objects in the distant, young universe are quasars. These cosmic beacons are powered by supermassive black holes consuming material at a ferocious rate. Quasars are so bright that they can outshine their entire host galaxy, making it difficult to study those galaxies and compare them to galaxies without quasars.

A new theoretical study examines how well NASA’s upcoming James Webb Space Telescope, slated for launch in 2021, will be able to separate the light of host galaxies from the bright central quasar. The researchers find that Webb could detect host galaxies that existed just 1 billion years after the big bang.

Quasars are the brightest objects in the universe and among the most energetic.

Now iconic image of a quasar.

They outshine entire galaxies of billions of stars. A supermassive black hole lies at the heart of every quasar, but not every black hole is a quasar. Only the black holes that are feeding most voraciously can power a quasar. Material falling into the supermassive black hole heats up, and causes a quasar to fiercely shine across the universe like a lighthouse beacon.

Although quasars are known to reside at the centers of galaxies, it’s been difficult to tell what those galaxies are like and how they compare to galaxies without quasars. The challenge is that the quasar’s glare makes it difficult or impossible to tease out the light of the surrounding host galaxy. It’s like looking directly into a car headlight and trying to figure out what kind of automobile it is attached to.

A new study [MNRAS] suggests that NASA’s James Webb Space Telescope, set to launch in 2021, will be able to reveal the host galaxies of some distant quasars despite their small sizes and obscuring dust.

“We want to know what kind of galaxies these quasars live in. That can help us answer questions like: How can black holes grow so big so fast? Is there a relationship between the mass of the galaxy and the mass of the black hole, like we see in the nearby universe?” said lead author Madeline Marshall of the University of Melbourne in Australia, who conducted her work within the ARC Centre of Excellence in All Sky Astrophysics in 3D (AU).

Answering these questions is challenging for a number of reasons. In particular, the more distant a galaxy is, the more its light has been stretched to longer wavelengths by the expansion of the universe. As a result, ultraviolet light from the black hole’s accretion disk or the galaxy’s young stars gets shifted to infrared wavelengths.

In a recent study [The Astrophysical Journal], astronomers used the near-infrared capabilities of NASA’s Hubble Space Telescope to study known quasars in hopes of spotting the surrounding glow of their host galaxies, without significant detections. This suggests that dust within the galaxies is obscuring the light of their stars. Webb’s infrared detectors will be able to peer through the dust and uncover the hidden galaxies.

“Hubble simply doesn’t go far enough into the infrared to see the host galaxies. This is where Webb will really excel,” said Rogier Windhorst of Arizona State University in Tempe, a co-author on the Hubble study.

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

“BlueTides is designed to study the formation and evolution of galaxies and quasars in the first billion years of the universe’s history. Its large cosmic volume and high spatial resolution enables us to study those rare quasar hosts on a statistical basis,” said Yueying Ni of Carnegie Mellon University, who ran the BlueTides simulation. BlueTides provides good agreement with current observations and allows astronomers to predict what Webb should see.

The team found that the galaxies hosting quasars tended to be smaller than average, spanning only about 1/30 the diameter of the Milky Way despite containing almost as much mass as our galaxy. “The host galaxies are surprisingly tiny compared to the average galaxy at that point in time,” said Marshall.

The galaxies in the simulation also tended to be forming stars rapidly, up to 600 times faster than the current star formation rate in the Milky Way. “We found that these systems grow very fast. They’re like precocious children – they do everything early on,” explained co-author Di Matteo.

The team then used these simulations to determine what Webb’s cameras would see if the observatory studied these distant systems. They found that distinguishing the host galaxy from the quasar would be possible, although still challenging due to the galaxy’s small size on the sky.

“Webb will open up the opportunity to observe these very distant host galaxies for the first time,” said Marshall.

They also considered what Webb’s spectrographs could glean from these systems. Spectral studies, which split incoming light into its component colors or wavelengths, would be able to reveal the chemical composition of the dust in these systems. Learning how much heavy elements they contain could help astronomers understand their star formation histories, since most of the chemical elements are produced in stars.

Webb also could determine whether the host galaxies are isolated or not. The Hubble study found that most of the quasars had detectable companion galaxies, but could not determine whether those galaxies were actually nearby or whether they are chance superpositions. Webb’s spectral capabilities will allow astronomers to measure the redshifts, and hence distances, of those apparent companion galaxies to determine if they are at the same distance as the quasar.

Ultimately, Webb’s observations should provide new insights into these extreme systems. Astronomers still struggle to understand how a black hole could grow to weigh a billion times as much as our Sun in just a billion years. “These big black holes shouldn’t exist so early because there hasn’t been enough time for them to grow so massive,” said co-author Stuart Wyithe of the University of Melbourne.

Future quasar studies will also be fueled by synergies among multiple upcoming observatories. Infrared surveys with the European Space Agency’s Euclid mission, as well as the ground-based Vera C. Rubin Observatory, a National Science Foundation/Department of Energy facility currently under construction on Cerro Pachón in Chile’s Atacama Desert. Both observatories will significantly increase the number of known distant quasars. Those newfound quasars will then be examined by Hubble and Webb to gain new understandings of the universe’s formative years.

The Bluetides simulation (project PI: Tiziana Di Matteo at Carnegie Mellon University) was run at the Blue Waters sustained-petascale computing facility, which is supported by the National Science Foundation.

NCSA U Illinois Urbana-Champaign Blue Waters Cray Linux XE/XK hybrid machine supercomputer, at the National Center for Supercomputing Applications.

See the full article here .


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The James Webb Space Telescope will be a large infrared telescope with a 6.5-meter primary mirror. Launch is planned for later in the decade.

Webb telescope will be the premier observatory of the next decade, serving thousands of astronomers worldwide. It will study every phase in the history of our Universe, ranging from the first luminous glows after the Big Bang, to the formation of solar systems capable of supporting life on planets like Earth, to the evolution of our own Solar System.

Webb telescope was formerly known as the “Next Generation Space Telescope” (NGST); it was renamed in Sept. 2002 after a former NASA administrator, James Webb.

Webb is an international collaboration between NASA, the European Space Agency (ESA), and the Canadian Space Agency (CSA). The NASA Goddard Space Flight Center is managing the development effort. The main industrial partner is Northrop Grumman; the Space Telescope Science Institute will operate Webb after launch.

Several innovative technologies have been developed for Webb. These include a folding, segmented primary mirror, adjusted to shape after launch; ultra-lightweight beryllium optics; detectors able to record extremely weak signals, microshutters that enable programmable object selection for the spectrograph; and a cryocooler for cooling the mid-IR detectors to 7K.

There will be four science instruments on Webb: the Near InfraRed Camera (NIRCam), the Near InfraRed Spectrograph (NIRspec), the Mid-InfraRed Instrument (MIRI), and the Fine Guidance Sensor/ Near InfraRed Imager and Slitless Spectrograph (FGS-NIRISS). Webb’s instruments will be designed to work primarily in the infrared range of the electromagnetic spectrum, with some capability in the visible range. It will be sensitive to light from 0.6 to 28 micrometers in wavelength.


NASA Webb NIRspec.


CSA Webb Fine Guidance Sensor-Near InfraRed Imager and Slitless Spectrograph FGS/NIRISS.

Webb has four main science themes: The End of the Dark Ages: First Light and Reionization, The Assembly of Galaxies, The Birth of Stars and Protoplanetary Systems, and Planetary Systems and the Origins of Life.

Launch is scheduled for later in the decade on an Ariane 5 rocket. The launch will be from Arianespace’s ELA-3 launch complex at European Spaceport located near Kourou, French Guiana. Webb will be located at the second Lagrange point, about a million miles from the Earth.

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