NASA’s Webb Will Use Quasars to Unlock the Secrets of the Early Universe

Quasars are very bright, distant and active supermassive black holes that are millions to billions of times the mass of the Sun. Typically located at the centers of galaxies, they prey on infalling matter and unleash fantastic torrents of radiation. Among the brightest objects within the universe, a quasar’s light outshines that of all the stars in its host galaxy combined, and its jets and winds shape the galaxy in which it resides.

Shortly after its launch later this year, a team of scientists will train NASA’s James Webb Space Telescope on six of the foremost distant and luminous quasars. They will study the properties of those quasars and their host galaxies, and the way they’re interconnected during the primary stages of galaxy evolution within the very early universe.

The team also will use the quasars to look at the gas within the space between galaxies, particularly during the amount of cosmic reionization, which ended when the universe was very young. They will accomplish this using Webb’s extreme sensitivity to low levels of sunshine and its superb angular resolution.

Webb: Visiting the Young Universe

As Webb peers deep into the universe, it’ll actually reminisce in time. Light from these distant quasars began its journey to Webb when the universe was very young and took billions of years to arrive. We will see things as they were way back , not as they’re today.

“All these quasars we are studying existed very early, when the universe was less than 800 million years old, or less than 6 percent of its current age. So these observations give us the chance to review galaxy evolution and supermassive black hole formation and evolution at these very early times,” explained team member Santiago Arribas, a research professor at the Department of Astrophysics of the Center for Astrobiology in Madrid, Spain. Arribas is also a member of Webb’s Near-Infrared Spectrograph (NIRSpec) Instrument Science Team.

The light from these very distant objects has been stretched by the expansion of space. This is known as cosmological redshift. The farther the light has to travel, the more it’s redshifted. In fact, the visible light emitted at the first universe is stretched so dramatically that it’s shifted out into the infrared when it arrives to us. With its suite of infrared-tuned instruments, Webb is uniquely suited to studying this type of light.

Studying Quasars, Their Host Galaxies and Environments, and Their Powerful Outflows

The quasars the team will study aren’t only among the foremost distant within the universe, but also among the brightest. These quasars typically have the very best black hole masses, and that they even have the highest accretion rates — the rates at which material falls into the black holes.

“We’re curious about observing the foremost luminous quasars because the very high amount of energy that they’re generating down at their cores should result in the largest impact on the host galaxy by the mechanisms such as quasar outflow and heating,” said Chris Willott, a research scientist at the Herzberg Astronomy and Astrophysics Research Centre of the National Research Council of Canada (NRC) in Victoria, British Columbia. Willott is additionally the Canadian Space Agency’s Webb project scientist. “We want to watch these quasars at the instant when they’re having the biggest impact on their host galaxies.”

An enormous amount of energy is liberated when matter is accreted by the supermassive black hole. This energy heats and pushes the surrounding gas outward, generating strong outflows that tear across interstellar space like a tsunami, wreaking havoc on the host galaxy.

Outflows play an important role in galaxy evolution. Gas fuels the formation of stars, so when gas is removed because of outflows, the star-formation rate decreases. In some cases, outflows are so powerful and expel such large amounts of gas that they will completely halt star formation within the host galaxy.

Scientists also think that outflows are the most mechanism by which gas, dust and elements are redistributed over large distances within the galaxy or can even be expelled into the space between galaxies – the intergalactic medium. This may provoke fundamental changes within the properties of both the host galaxy and therefore the intergalactic medium.

Examining Properties of Intergalactic Space During the Era of Reionization

More than 13 billion years ago, when the universe was very young, the view was far from clear. Neutral gas between galaxies made the universe opaque to some kinds of light. Over hundreds of millions of years, the neutral gas within the intergalactic medium became charged or ionized, making it transparent to ultraviolet .

This period is called the Era of Reionization. But what led to the reionization that created the “clear” conditions detected in much of the universe today? Webb will peer deep into space to collect more information about this major transition within the history of the universe. The observations will help us understand the era of Reionization, which is one among the key frontiers in astrophysics.

The team will use quasars as background light sources to study the gas between us and also the quasar. That gas absorbs the quasar’s light at specific wavelengths. Through a way called imaging spectroscopy, they’re going to search for absorption lines within the intervening gas.

The brighter the quasar is, the stronger those absorption line features are within the spectrum. By determining whether the gas is neutral or ionized, scientists will find out how neutral the universe is and the way much of this reionization process has occurred at that specific point in time.

“If you want to study the universe, you need very bright background sources. A quasar is that the perfect object within the distant universe, because it’s luminous enough that we will see it fine,” said team member Camilla Pacifici, who is affiliated with the Canadian Space Agency but works as an instrument scientist at the Space Telescope Science Institute in Baltimore. “We want to study the first universe because the universe evolves, and that we want to know how it got started.”

The Power of Webb

The team will analyze the light coming from the quasars with NIRSpec to appear for what astronomers call “metals,” which are elements heavier than hydrogen and helium. These elements were formed within the first stars and the first galaxies and expelled by outflows.

The gas moves out of the galaxies it had been originally in and into the intergalactic medium. The team plans to measure the generation of those first “metals,” as well as the way they’re being pushed out into the intergalactic medium by these early outflows.

Webb is a particularly sensitive telescope ready to detect very low levels of light. this is often important, because although the quasars are intrinsically very bright, those this team goes to observe are among the foremost distant objects within the universe.

In fact, they’re so distant that the signals Webb will receive are very, very low. Only with Webb’s exquisite sensitivity can this science be accomplished. Webb also provides excellent angular resolution, making it possible to disentangle the light of the quasar from its host galaxy.

The quasar programs described here are Guaranteed Time Observations involving the spectroscopic capabilities of NIRSpec.

The James Webb Space Telescope will be the world’s premier space science observatory when it launches in 2021. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is a world program led by NASA with its partners, ESA (European Space Agency) and therefore the Canadian Space Agency.