The Universe is full of massive galaxies like ours, but astronomers don’t fully understand how they grew and evolved. They know that the first galaxies formed at least as early as 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 the growth of galaxies, but they don’t know precisely how.
A new Hubble survey of galaxies should help astronomers figure some of this out.
The survey is called 3D-Drift And SHift (3D-DASH.) 3D-DASH is a high-resolution near-infrared imaging and spectrometry survey of the sky that maps star-forming regions. It’s the largest of its kind. The goal is to find rare galactic objects that the James Webb Space Telescope can target in follow-up observations.
A paper titled “3D-DASH: The Widest Near-Infrared Hubble Space Telescope Survey” presents the new mosaic. It’ll be published in The Astrophysical Journal and is currently available at the pre-press site arxiv.org. The lead author is Lamiya Mowla, Dunlap Fellow at the Faculty of Arts & Science’s Dunlap Institute for Astronomy & Astrophysics at the University of Toronto.
“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 the lead author Mowla. “The 3D-DASH program extends Hubble’s legacy in wide-area imaging so we can begin to unravel the mysteries of the galaxies beyond our own.”
3D-DASH is an improvement on an earlier effort called COSMOS. COSMOS covered a 2 square degree equatorial field using multiple space-based and ground-based telescopes, using spectroscopy, x-ray, and radio imaging. It contains over 2 million galaxies that span 75% of the age of the Universe.
This image shows the patch of sky covered by COSMOS, the predecessor to 3D-DASH. 3D-DASH will cover the same chunk of the sky but add near-infrared observations. Image Credit: COSMOS/Caltech.
3D-DASH improves on COSMOS by surveying its entire contents in near-infrared. That’s significant because it allows astronomers to see the most distant, earliest galaxies.
Survey size is critical in the study of galaxies. To be productive, surveys have to identify unique phenomena in the Universe: the most massive galaxies, the oldest galaxies, and galaxies on the verge of merging are critical to expanding our understanding of galaxies. So are highly active black holes. But to find those, astronomers need huge images that they can comb through.
This is the 3D-DASH mosaic. The zoomed-in panels reveal the wealth of bright objects that astronomers can study in this high-resolution shallow tier of the extragalactic wedding cake. Image Credit: Mowla et al. 2022.
Previous surveys weren’t as robust because they were ground-based. They suffered from low resolution, limiting what astronomers could learn from them. 3D-DASH doesn’t suffer from those same limitations.
“I am curious about giant galaxies, which are the most massive ones in the Universe formed by the mergers of other galaxies. How did their structures grow, and what drove the changes in their form?” says Mowla, who began work on the project in 2015 while a grad 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 close pairs of galaxies. They’re critical for studying the evolution of galaxy merger 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 that are then stitched together into one enormous image. DASH is a huge time-saver and took images in 250 hours that previously would’ve taken 2000 hours.
It does this by capturing eight images per Hubble orbit rather than one. Only the first of each of the eight images is pointed, and the following seven are unguided and taken while the Hubble “drifts and shifts.” The technique means that the data reduction procedures are more demanding, but the result is worth it.
“3D-DASH adds a new layer of unique observations in the COSMOS field and is also a steppingstone to the space surveys of 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 sneak peek of future scientific discoveries and allows us to develop new techniques to analyze these large datasets.“
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 kiloparsecs square. Image Credit: Mowla et al. 2022.
3D-DASH provides a list of galactic targets for the James Webb Space Telescope, which should start science observations soon. The ‘Early Universe‘ and ‘Galaxies Over Time‘ are two of the JWST’s overarching science objectives. “Webb’s unprecedented infrared sensitivity will help astronomers to compare the faintest, earliest galaxies to today’s grand spirals and ellipticals, helping us to understand how galaxies assemble over billions of years,” NASA writes. The list of targets from 3D-DASH will help advance those objectives.
You can explore an online version of the mosaic here.
NAIROBI, Kenya (AP) — The body of Ugandan Olympic athlete Rebecca Cheptegei — who died after being set on fire by her partner in Kenya — was received Friday by family and anti-femicide crusaders, ahead of her burial a day later.
Cheptegei’s family met with dozens of activists Friday who had marched to the Moi Teaching and Referral Hospital’s morgue in the western city of Eldoret while chanting anti-femicide slogans.
She is the fourth female athlete to have been killed by her partner in Kenya in yet another case of gender-based violence in recent years.
Viola Cheptoo, the founder of Tirop Angels – an organization that was formed in honor of athlete Agnes Tirop, who was stabbed to death in 2021, said stakeholders need to ensure this is the last death of an athlete due to gender-based violence.
“We are here to say that enough is enough, we are tired of burying our sisters due to GBV,” she said.
It was a somber mood at the morgue as athletes and family members viewed Cheptegei’s body which sustained 80% of burns after she was doused with gasoline by her partner Dickson Ndiema. Ndiema sustained 30% burns on his body and later succumbed.
Ndiema and Cheptegei were said to have quarreled over a piece of land that the athlete bought in Kenya, according to a report filed by the local chief.
Cheptegei competed in the women’s marathon at the Paris Olympics less than a month before the attack. She finished in 44th place.
Cheptegei’s father, Joseph, said that the body will make a brief stop at their home in the Endebess area before proceeding to Bukwo in eastern Uganda for a night vigil and burial on Saturday.
“We are in the final part of giving my daughter the last respect,” a visibly distraught Joseph said.
He told reporters last week that Ndiema was stalking and threatening Cheptegei and the family had informed police.
Four in 10 women or an estimated 41% of dating or married Kenyan women have experienced physical or sexual violence perpetrated by their current or most recent partner, according to the Kenya Demographic and Health Survey 2022.
TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.
Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.
Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.
The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.
The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.
It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.
Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.
Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.
Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.
Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.
Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.
The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”
VICTORIA – The British Columbia government is partnering with a bear welfare group to reduce the number of bears being euthanized in the province.
Nicholas Scapillati, executive director of Grizzly Bear Foundation, said Monday that it comes after months-long discussions with the province on how to protect bears, with the goal to give the animals a “better and second chance at life in the wild.”
Scapillati said what’s exciting about the project is that the government is open to working with outside experts and the public.
“So, they’ll be working through Indigenous knowledge and scientific understanding, bringing in the latest techniques and training expertise from leading experts,” he said in an interview.
B.C. government data show conservation officers destroyed 603 black bears and 23 grizzly bears in 2023, while 154 black bears were killed by officers in the first six months of this year.
Scapillati said the group will publish a report with recommendations by next spring, while an independent oversight committee will be set up to review all bear encounters with conservation officers to provide advice to the government.
Environment Minister George Heyman said in a statement that they are looking for new ways to ensure conservation officers “have the trust of the communities they serve,” and the panel will make recommendations to enhance officer training and improve policies.
Lesley Fox, with the wildlife protection group The Fur-Bearers, said they’ve been calling for such a committee for decades.
“This move demonstrates the government is listening,” said Fox. “I suspect, because of the impending election, their listening skills are potentially a little sharper than they normally are.”
Fox said the partnership came from “a place of long frustration” as provincial conservation officers kill more than 500 black bears every year on average, and the public is “no longer tolerating this kind of approach.”
“I think that the conservation officer service and the B.C. government are aware they need to change, and certainly the public has been asking for it,” said Fox.
Fox said there’s a lot of optimism about the new partnership, but, as with any government, there will likely be a lot of red tape to get through.
“I think speed is going to be important, whether or not the committee has the ability to make change and make change relatively quickly without having to study an issue to death, ” said Fox.
This report by The Canadian Press was first published Sept. 9, 2024.
