Tuesday, May 28, 2024

Thousands of other potential lenses are waiting for evaluation

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Jillian Castillo
Jillian Castillo
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Earlier this year, a machine learning algorithm identified up to 5,000 potential gravitational lenses that could transform our ability to track the evolution of galaxies since the Big Bang.

Now, astronomer Kim-Vy Tran and colleagues from ASTRO 3D and UNSW Sydney have evaluated 77 lenses using the Keck Observatory in Hawaii and the Very Large Telescope in Chile. She and her international team confirmed that 68 of the 77 strong gravitational lenses span vast cosmic distances.

The success rate of 88% indicates that the algorithm is reliable and that we can obtain thousands of new gravitational lenses. To date, gravitational lenses are difficult to find and only about 100 lenses are commonly used.

The Kim-Vy Tran paper published today in the Astronomical Journal provides spectroscopic confirmation of previously identified strong gravitational lenses using convolutional neural networks, developed by ASTRO 3D data scientist Dr. Colin Jacobs and Swinburne University.

This work is part of the ASTRO 3D Galaxy Evolution with Lenses (AGEL) survey.

“Our spectroscopy allowed us to map a 3D image of gravitational lenses to show that they are authentic and not just a coincidental overlay,” says corresponding author Dr. Tran of the Center of Excellence in Sky Astrophysics at ARC. in 3D (ASTRO3D) and the University of New South Wales (UNSW).

“Our goal with AGEL is to confirm, through spectroscopy, approximately 100 strong gravitational lenses that are observable from the northern and southern hemispheres throughout the year,” she says.

The article is the result of a global collaboration with researchers from Australia, the United States, the United Kingdom, and Chile.

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The work was made possible by developing a search algorithm for some digital signatures.

“With this, we were able to identify several thousand lenses for just a few handfuls,” says Dr. Tran.

Gravitational lensing was first identified as a phenomenon by Einstein who predicted that light bends around massive objects in space in the same way that light bends when passing through a lens.

By doing so, it greatly expands the images of galaxies that we would not otherwise be able to see.

While it has been used by astronomers to observe distant galaxies for a long time, finding these cosmic magnifying glasses in the first place has been a shock and fail.

“These lenses are very small, so if you have blurry images, you really won’t be able to detect it,” Dr. Tran says.

While these lenses allow us to see things millions of light years away more clearly, they should also allow us to “see” the invisible dark matter that makes up most of the universe.

“We know that most of the mass is dark,” Dr. Tran says. “We know that mass makes the light bend, so if we can measure how much the light is bending, we can infer how much mass there should be.”

Having so many gravitational lenses at different distances would also give us a fuller picture of the timeline dating roughly back to the Big Bang.

“The more magnifying you have, the more likely you are to try to study these distant objects. Hopefully we can measure the demographics of very young galaxies,” says Dr. Tran.

“Then somewhere between those very early first galaxies and us, a lot of evolution is happening, as small regions of star formation funnel the original gas into the first stars from the Sun, the Milky Way.

“So, with these lenses at different distances, we can look at different points in the cosmic timeline to basically track how things change over time, between the first galaxies and now.”

Dr. Tran’s team spanned the globe, with each group bringing different expertise.

“Being able to collaborate with people, in different universities, was critical, both for setting up the project in the first place, and now for following up on all of the follow-up feedback,” she says.

Each gravitational lens is unique and teaches us something new, says Professor Stuart Wyeth of the University of Melbourne and director of ARC’s Center of Excellence in Astrophysics in 3 Dimensions (Astro 3D).

In addition to being beautiful objects, gravitational lenses provide a window into how mass is distributed in galaxies too far away to be observed by other techniques. By offering ways to use these new large sky data sets to search for many new gravitational lenses, the team opens up the possibility of seeing how galaxies gain their mass, he says.

Professor Karl Glazbrook of Swinburne University and Dr Tran’s scientist, co-author of the paper, praised the work done before.

“This algorithm was developed by Dr. Colin Jacobs at Swinburne. He scanned tens of millions of images of galaxies to reduce the sample to 5,000. We never imagined that the success rate would be so high,” he says.

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“Now we are getting images of these lenses with the Hubble Space Telescope, and they range from stunningly beautiful images to extremely frightening ones that require a great deal of effort to understand.”

UC Davis Associate Professor Tucker-Jones, another co-scientist on the paper, described the new sample as “a giant leap in learning about the formation of galaxies throughout space history.” “Universe”.

Normally, these early galaxies look like tiny blurry spots, but the magnification of the lens allows us to see their structure with much better resolution. They are ideal targets for our most powerful telescopes to give us the best possible view of the early universe,” he says.

“Through the lens, we can learn what these early galaxies looked like, what their components were, and how they interact with their environment.”

The study was conducted in collaboration with researchers from the University of New South Wales, Swinburne University of Technology, Australian National University, Curtin University, University of Queensland in Australia, University of California at Davis in the United States, and the University of Portsmouth. , United Kingdom, and the University of Chile.

The ARC Center of Excellence for All Astrophysics in 3D (ASTRO 3D) is a $40 million center of research excellence funded by the Australian Research Council (ARC) and six Australian collaborating universities – National University Australia, University of Sydney, University of Melbourne, Swinburne University of Technology, and University of Australia Western and Curtin University.

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