When the Universe Was Six Billion Years Old

Most “mature” galaxies, such as our own Milky Way and others that have been around for 10 or 12 billion years, are shaped like a disk with a big bulge in the middle. But when they’re being formed, most galaxies aren’t nearly so symmetrical. In fact, says astronomy prof. Debra Elmegreen, “they’re kind of  ‘clumpy,’ dominated by massive regions of forming stars.”

Professor of Astronomy Debra Elmegreen with Brittany Tompkins ’17 (right) and Leah Jenks (left)

This summer, Elmegreen and two students enrolled in Vassar’s Undergraduate Research Summer Institute (URSI) are studying some of these ‘clumpy’ galaxies that first became visible to astronomers through the Hubble Space Telescope, which was launched in 1990.

“The Hubble is taking pictures of galaxies in deep space that we’ve never been able to see before,” Elmegreen says. “The universe is about 13.8 billion years old, and now we’re seeing galaxies that are 6 billion years old or less for the first time.”

As part of her own ongoing research, Elmegreen has assigned each of her URSI students, Brittany Tompkins ’17 and Colgate University senior Leah Jenks, the task of identifying galaxies in two “Frontier Fields,” Hubble’s most recent deep images. They’ve each discovered about 100 of these clumpy galaxies, and are measuring and analyzing their properties. Studying these younger galaxies will help astronomers understand how galaxies evolve, Elmegreen says. “By analyzing how the light in these galaxies is distributed in different wavelengths, you can determine the shape and thickness of the disk,” she explains. “As galaxies age, the disk becomes less turbulent and larger, and some become more like the spiral disk of the Milky Way.”

Tompkins, a physics and astronomy double major from Poughkeepsie, NY, says she gained some knowledge about the formation of galaxies in earlier astronomy classes at Vassar, but this summer she’s learning how to gather a lot of information about the younger galaxies that are now visible via the Hubble telescope. Using specially designed software, Tompkins and Jenks can determine the detailed distributions of light in galaxies observed as they were when the universe was less than half its current age.

“The universe is expanding, so the light from these galaxies gets stretched into longer wavelengths,” Jenks explains. “By looking at the red end of the light spectrum, we are actually seeing blue light emitted from the galaxies at redshift 1, and can compare the disk properties with nearby galaxies to see how they have changed with time.”

Tompkins and Jenks examining Hubble data

Jenks, an astronomy and physics double major from Chicago, joined Tompkins and Elmegreen on the Vassar URSI team through the National Science Foundation-funded Keck Northeast Astronomy Consortium, a group of colleges and universities whose students and faculty collaborate on astronomy projects. Vassar and Colgate are two members of the eight-college consortium. Jenks and Tompkins will report on the research they’re doing this summer at the consortium’s annual student symposium, which will be held in October at Wesleyan University in Middletown, CT. They’ll also report their findings at the URSI symposium this fall on the Vassar campus.

Jenks says she plans to focus on other areas of physics when she goes to graduate school but is grateful for the opportunity to work all summer with a revered, veteran astronomer. “Having Professor Elmegreen as a mentor this summer has been a great experience,” she says.

Tompkins, who plans to pursue a career in teaching, agreed. “This is my first real, in-depth research experience, and it will really help me in the classroom to have done something like this,” she says. “Up until now, I have been focusing more on teaching physics. For my high school students, having this experience will provide me with a great jumping off point in the classroom, because kids get excited about astronomy.”

Elmegreen says Tompkins and Jenks are helping her make significant progress in her research. “I’m part of a small group of astronomers working on this project, and Brittany and Leah have really become a part of the team,” she says. “I can’t always advance my research using URSI students, but with Brittany and Leah, I knew I was getting two rising seniors with solid backgrounds who could do the work I would have had to do on these 200 galaxies. And they often find ways of doing it faster and more efficiently than I would.”

--Larry Hertz

Photos by Karl Rabe

Posted by Office of Communications Tuesday, July 12, 2016