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 fusions play a role in the growth of galaxies. Astronomers also know that supermassive black holes are involved in the growth of galaxies, but they do not know exactly how.
A new survey of Hubble galaxies should help astronomers find out.
The survey is called 3D-Drift And SHift (3D-DASH.) 3D-DASH is a survey of near-high-resolution near-infrared spectrometry and imaging that maps star-forming regions. It is the largest of its kind. The goal is to find rare galactic objects that the James Webb Space Telescope can orient in tracking observations.
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An article titled “3D-DASH: The Widest Near-Infrared Space Telescope Survey Hubble” features the new mosaic. It will be published in The Astrophysical Journal and is currently available on the press site arxiv.org. The lead author is Lamiya Mowla, a Dunlap Fellow at the Dunlap Institute of Astronomy and Astrophysics at the University of Toronto School of Arts and Sciences.
“Since its launch more than 30 years ago, the Hubble Space Telescope has led a renaissance in the study of how galaxies have changed in the last 10 billion years of the universe,” said lead author Mowla . “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 enhancement of a previous effort called COSMOS. COSMOS covered an equatorial field of 2 square degrees using multiple space and ground telescopes, using spectroscopy, X-rays, and radio imaging. It contains more than 2 million galaxies spanning 75% of the age of the Universe.
This image shows the patch of sky covered by COSMOS, the predecessor of 3D-DASH. 3D-DASH will cover the same part of the sky but add near-infrared observations. Image credit: COSMOS / Caltech.
3D-DASH enhances COSMOS by examining all of its near-infrared content. This is important because it allows astronomers to see the most distant and early galaxies.
The size of the survey is crucial in the study of galaxies. To be productive, surveys must identify phenomena unique to the Universe: the most massive galaxies, the oldest galaxies, and the fading galaxies are critical to broadening our understanding of galaxies. So are the highly active black holes. But to find them, astronomers need huge images that they can comb.
This is the 3D-DASH mosaic. The enlarged panels reveal the richness of bright objects that astronomers can study at this shallow high-resolution level of the extragalactic wedding cake. Image Credit: Mowla et al. 2022.
Previous surveys were not as robust because they were ground-based. They suffered from low resolution, limiting what astronomers could learn from them. 3D-DASH does not suffer from these same limitations.
“I am curious about the giant galaxies, which are the most massive in the universe formed by the fusion of other galaxies. How did their structures grow and what drove the changes in their shape? says Mowla, who began working on the project in 2015 while a graduate student at Yale University. “It was difficult to study these extremely rare events using existing images, which is what motivated the design of this large survey.”
3D-DASH allowed astronomers to create a census of rare pairs of nearby galaxies. They are critical to studying the evolution of galaxy fusion rates. These galaxy pairs are separated by 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 taking a panoramic image with a smartphone. The method captures multiple images which are then merged into a huge image. DASH is a great time saver and took pictures in 250 hours which would have taken 2000 hours before.
It does this by capturing eight Hubble orbit images instead of one. Only the first of each of the eight images is pointed, and the next seven are unguided and taken while Hubble “drifts and changes.” The technique makes data reduction procedures 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 stepping stone to space surveys for the next decade,” says Ivelina Momcheva, head of data science at the Max Planck Institute for Astronomy and principal investigator of the study. “It gives us a glimpse 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 the rare massive star-forming galaxies in the last 5 Gyrs. Each of these images is 40 square kiloparsecs. Image Credit: Mowla et al. 2022.
3D-DASH provides a list of galactic targets for the James Webb Space Telescope, which should begin scientific observations soon. The “Early Universe” and “Galaxies Over Time” are two of JWST’s general scientific goals. “Webb’s unprecedented infrared sensitivity will help astronomers compare the earliest and weakest galaxies with today’s large spirals and ellipticals, helping us to understand how galaxies look like billions of years ago,” he writes. NASA. The 3D-DASH goal list will help you move forward on those goals.
You can explore an online version of the mosaic here.
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