The universe is full of massive galaxies like ours, but astronomers do not fully understand how they grew and evolved. They know that the first galaxies formed at least 670 million years after the Big Bang. They know that mergers play a role in the growth of galaxies. Astronomers also know that supermassive black holes are involved in galaxy growth, but they don’t know exactly how.
A new study of Hubble’s galaxies should help astronomers understand some of this.
The study is called 3D-Drift And SHift (3D-DASH.) 3D-DASH is a close-up infrared image and high-resolution spectrometric study of the sky that maps star-forming regions. This is the largest of its kind. The goal is to find rare galactic objects that the James Webb Space Telescope can target in subsequent observations.
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A paper entitled “3D-DASH: The Widest Exploration of the Hubble Space Telescope Near Infrared” presents the new mosaic. It will be published in The Astrophysical Journal and is currently available on the prepress site arxiv.org. The lead author is Lamia Moula, an associate of Dunlap at the Faculty of Arts and Sciences at the Dunlap Institute of Astronomy and Astrophysics at the University of Toronto.
“Since its launch more than 30 years ago, the Hubble Space Telescope has led to a renaissance in the study of how galaxies have changed over the last 10 billion years of the universe,” said lead author Maula. “The 3D-DASH program expands Hubble’s legacy into wide-area imagery so we can begin to unravel the mysteries of galaxies beyond our own.”
3D-DASH is an improvement on an earlier effort called COSMOS. COSMOS covers an equatorial field of 2 square degrees, using multiple space and ground-based telescopes, using spectroscopy, X-rays and radio images. It contains over 2 million galaxies, which cover 75% of the age of the universe.
This image shows the area of the sky covered by COSMOS, the forerunner of 3D-DASH. 3D-DASH will cover the same part of the sky, but will add almost infrared observations. Image credit: COSMOS / Caltech.
3D-DASH improves COSMOS by examining all its contents in near infrared. This is important because it allows astronomers to see the most distant, earliest galaxies.
The size of the study is crucial in the study of galaxies. To be productive, research must identify unique phenomena in the universe: the most massive galaxies, the oldest galaxies, and fringe-edge galaxies are crucial to expanding our understanding of galaxies. Such are the highly active black holes. But to find them, astronomers need huge images to view.
This is the 3D-DASH mosaic. The enlarged panels reveal a wealth of bright objects that astronomers can study in this shallow, high-resolution layer of the extragalactic wedding cake. Image credit: Mowla et al. 2022
Previous studies were less stable because they were terrestrial. They suffered from low resolution, limiting what astronomers could learn from them. 3D-DASH does not suffer from the same limitations.
“I’m curious about the giant galaxies, which are the most massive in the universe, formed by the merging of other galaxies. How have their structures grown and what has changed their shape? ”Says Maula, who began working on the project in 2015 while a student at Yale University. “It was difficult to study these extremely rare events using existing images, which motivated the design of this large study.”
3D-DASH allowed astronomers to create a census of rare close pairs of galaxies. They are crucial for studying the evolution of the degree of merging of galaxies. These pairs of galaxies are divided into less than 20 kiloparsecs. Image credit: Mowla et al. 2022
DASH stands for Drift And SHift, the name of the new imaging technique that Mowla and her colleagues. DASH is similar to capturing a panoramic image with a smartphone. The method captures multiple images, which are then merged into one huge image. DASH saves a lot of time and takes pictures in 250 hours, which would have taken 2,000 hours before.
He did this by capturing eight images in Hubble’s orbit, not one. Only the first of each of the eight images is aimed, and the next seven are unfocused and captured while Hubble “moves and moves.” The technique means that data reduction procedures are more demanding, but the result is worth it.
“3D-DASH adds a new layer of unique observations to the COSMOS field and is also a step towards space research over the next decade,” said Ivelina Momcheva, head of data science at the Max Planck Institute for Astronomy and lead researcher. “This gives us a brief overview of future scientific discoveries and allows us to develop new techniques for analyzing these large data sets.”
3D-DASH also allowed astronomers to create a census of the most active star-forming regions of rare massive star-forming galaxies over the past 5 Gyrs. Each of these images is 40 kiloparsecs square. Image credit: Mowla et al. 2022
3D-DASH provides a list of galactic targets for the James Webb Space Telescope, which is about to begin scientific observations. Early Universe and Time Galaxies are two of JWST’s overarching scientific goals. “The unprecedented infrared sensitivity of the Web will help astronomers compare the weakest, earliest galaxies to today’s huge spirals and ellipses, helping us understand how galaxies have assembled over billions of years,” NASA wrote. The list of 3D-DASH goals will help achieve these goals.
You can view the online version of the mosaic here.
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