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Studying galaxy growth spurts in the early universe with NASA’s Roman

Exploring growth spurts in the early Universe with NASA's Roman

This Hubble image shows four of the thousands of galaxies found in the Hubble Ultra Deep Field. All highlighted galaxies show signs of powerful star formation (blue regions filled with hot, young stars). The inset on the right shows the near infrared spectrum of each galaxy. By examining a galaxy’s spectrum, you can learn about the age of its stars, the history of star formation, how many heavy chemical elements it contains, and more. When the Nancy Grace Roman Space Telescope becomes operational in 2027, it will be able to collect spectra for every object in its field of view, more than 100 times larger than Hubble’s. As a result, it will enable research into rare galaxies from a period known as “cosmic midday,” when many galaxies were experiencing growth spurts. Credit: Science: NASA, ESA, Casey Papovich (TAMU); Image Processing: Alyssa Pagan (STScI)

In the American Wild West, noon was a time for duels and showdowns. When it comes to the history of the universe, cosmic afternoon fireworks were of a different kind. Some 2 to 3 billion years after the Big Bang, most galaxies went through a growth spurt and formed stars at a rate hundreds of times faster than we see today in our own galaxy, the Milky Way. When it launches in May 2027, NASA’s Nancy Grace Roman Space Telescope promises to bring new insights into the heyday of star formation.

The cosmic noon is an important moment in the history of the Universe because it has shaped what galaxies look like today. But many questions remain unanswered. Why did star formation peak and then decline? Why did some galaxies suddenly stop forming stars, while others gradually faded? How important were local influences such as the number of galactic neighbors in shaping this evolution?

To answer these questions, astronomers need to study a copious amount of galaxies from that period. Roman’s strength lies in his ability to capture thousands of interesting objects at a glance. With such a large study, scientists don’t have to pick their favorite targets ahead of time, which can lead to unintended bias.

“With a field of view 100 times wider than the Hubble Space Telescope, Roman can change the astronomical landscape by being so efficient,” said Kate Whitaker, an assistant professor of astronomy at the University of Massachusetts at Amherst. Whitaker’s research focuses on studying the regulation of star formation and extinction in massive galaxies in the early Universe.

Roman’s wide field of view also allows astronomers to contextualize individual galaxies by seeing how their growth spurts and subsequent slowdowns vary depending on their location within the cosmic “web” — the large-scale structure of the universe.

“You take one picture and you get everything. We’ll see what and where the objects of interest are,” said Casey Papovich, an astronomy professor at Texas A&M University in College Station, Texas. Papovich’s research involves quantifying the growth and assembly of stellar masses in galaxies in the early Universe.

NASA’s Nancy Grace Roman Space Telescope will be a powerful tool for studying galaxies in the cosmos. It will be able to provide spectra for every galaxy in its field of view. And with a field of view 200 times that of the Hubble Space Telescope at infrared wavelengths, Roman can capture thousands of interesting objects in a single observation. Credit: Video: Robert Hurt (IPAC/Caltech); Hubble Ultra Deep Field Visualization Courtesy of Frank Summers (STScI)/NASA’s Universe of Learning; Music: “Red Giant” by Stellardrone

Going beyond imagery

While images can help astronomers spot interesting galaxies, much more information can be gathered by scattering a galaxy’s light in a spectrum. Papovich, together with Vicente (Vince) Estrada-Carpenter of St. Mary’s University in San Antonio, Texas, and their colleagues have developed a technique to extract the light from all the stars in a combined galaxy.

By examining a galaxy’s spectrum, you can learn about the age of its stars, the history of star formation, how many heavy chemical elements it contains, and more. By doing this for a large number of early galaxies, astronomers can learn about the processes that drove and ultimately ended this period of rapid growth.

Roman’s power can be increased even further by observing distant galaxies whose light has been distorted by a phenomenon called gravitational lensing. The gravitational pull of an intermediate galaxy cluster can magnify and brighten the light from a more distant galaxy, allowing astronomers to study the background galaxy in more detail than would otherwise be possible.

Whitaker is already using this technique with Hubble to study the cores of young galaxies versus their suburbs. This work attempts to determine whether star formation is shutting down from the outside in or from the inside out — that is, from the galaxy’s outskirts to the center or vice versa.

“Galaxy extinction — a sudden end to star formation — can be a rapid process on cosmological timescales. As a result, it’s hard to catch one in the act because they’re so rare,” Whitaker said. “Roman will help us find those rare examples.”

While Roman’s space image will provide excellent sharpness and stability, ground observatories will also play a role in studying the cosmic noon. For example, the Atacama Large Millimeter/submillimeter Array can measure the gas and dust content of distant galaxies. And future 30-meter-class telescopes will be able to measure beautiful detail in galaxy spectra because of their ability to collect a lot of light.

“Roman and ground-based observatories will complement each other. Roman will single-handedly and efficiently identify and characterize the most interesting galaxies in large fields of view. We can then go back with ground-based telescopes to study them in more detail.” explained Papovich.

Supermassive black holes in dying galaxies detected in early universe

Provided by NASA’s Goddard Space Flight Center

Quote: Exploring early universe galaxy growth spurts with NASA’s Novel (2022, June 27) retrieved June 27, 2022 from https://phys.org/news/2022-06-galaxy-growth-spurts-early-universe.html

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