Exploring Extragalactic Neighborhoods
by Jackie Swift
Martha P. Haynes, Astronomy at Cornell University, has achieved many milestones in her 37-year career at Cornell. She received the prestigious National Academy of Sciences’ Henry Draper Medal (together with Riccardo Giovanelli, emeritus professor of Astronomy) for the first three-dimensional view of the filamentary structure of the universe and the Catherine Wolfe Bruce Gold Medal of the Astronomical Society of the Pacific for lifetime achievement in astronomy. She even has an asteroid named after her. But what excites her the most these days is the new, groundbreaking telescope she will be leaving behind for the next generation of researchers.
CCAT-prime: A Next-Generation Telescope
Called the Cerro Chajnantor Atacama Telescope-prime (CCAT-prime), the six-meter (20 feet) diameter telescope based on designs pioneered by Michael D. Niemack, Physics/Astronomy, is situated at 18,400 feet in the Atacama Desert of Chile. Full installation will be completed in 2021. “CCAT-prime is a state-of-the-art frontier telescope that will be unique because of its high site and its very precise mirror,” Haynes explains. “It is designed to observe at short wavelengths — about a third of a millimeter to two millimeters — that are hard to observe on Earth because water vapor molecules in the atmosphere absorb these photons and block them from reaching the ground.”
Together with Giovanelli, Haynes came up with the idea in the mid-1990s to build a telescope like CCAT-prime on a very high peak in Chile, then helped bring the dream to fruition. She served as project director during the concept design phase and is currently chair of the board of directors for the not-for-profit corporation that now manages the telescope. But after almost 25 years of shepherding CCAT-prime into existence, she doesn’t expect to use it for research. “I went into phased retirement last July,” she says. “This project isn’t about building CCAT-prime for me; it’s about building it for the next generation of researchers. This is me giving back to make sure my young colleagues have an exciting new telescope to feed their research for the next 20 years.”
CCAT-prime is designed to explore three aspects of the universe on different scales: the origin and development of structure on large scales in the universe, the evolution of galaxies from early times to today, and the mechanism by which the local interstellar medium (diffuse clouds of gases and minute particles between stars) collapses to form stars. These are all questions relevant to Haynes’ own research, which throughout her career has focused on how current galaxies evolve in different environments.
“Where a galaxy finds itself in the universe has an influence on what it looks like, how it turns gas into stars, and the nature of its structure,” she says. “I think of it as extragalactic sociology — whether a galaxy is found in a village, a town, a city: things like that. How do you define extragalactic environment? How do you quantify it? And how do you measure galaxy evolution to tell that there’s a difference between galaxies found in different environments?”
Discovering the Cosmic Web
Haynes joined the astronomy department at Cornell in 1983 largely because of the Arecibo Observatory in Puerto Rico, which was under Cornell’s management. “I used Arecibo to do a lot of observational programs, many of which at the time were the first of their kind,” she says. “And I was involved in big surveys. That was the backbone of my work: studying the hydrogen gas in and between galaxies.”
“Where a galaxy finds itself in the universe has an influence on what it looks like…I think of it as extragalactic sociology — whether a galaxy is found in a village, a town, a city: things like that.”
Using Arecibo, she and Giovanelli made the discovery that the universe is made up of filaments, which led to the Henry Draper Medal. “We demonstrated that the universe is not a bunch of isolated clusters of galaxies, as people thought,” she says. “Rather, the distribution of galaxies trace out a filamentary, interconnected structure called the cosmic web. That finding was revolutionary in the 1980s; it’s not at all what was predicted at the time by models of how the structure of the universe developed.”
Detecting Unknown Galaxies
Arecibo remained Haynes’ go-to telescope throughout her career, and the telescope gained in power as it was upgraded over time. During the third upgrade, during the early 2000s, the telescope was outfitted with the Arecibo L Band Feed Array (ALFA), a seven-pixel radio camera. Using ALFA, Haynes and her collaborators embarked on the Arecibo Legacy Fast ALFA (ALFALFA) survey: 4,400 hours of observations carried out over almost seven years by more than 200 people. Many of those involved were students from Cornell and other institutions — including the Undergraduate ALFALFA Team, funded by the National Science Foundation and made up of undergraduates from approximately 20 schools around the United States and Puerto Rico.
“Before Arecibo was upgraded with ALFA, we had to observe one point at a time in the sky, and stare at each for around 15 minutes to see anything. It was very slow,” Haynes says. “For the ALFALFA survey, we mapped 15 percent of the sky and detected all of the gas-bearing galaxies that were there, not just the ones we pointed at. We detected galaxies we didn’t even know about beforehand.”
Now that ALFALFA is finished, Haynes and her colleagues are currently analyzing the data. They have already used it to make the first measurement of the cosmic abundance of hydrogen gas in the local universe over a large enough area to avoid skewing measurements based on the location of our Milky Way galaxy.
Calculating the Mass of the Pisces-Perseus Supercluster
Working with the Undergraduate ALFALFA Team, Haynes is following up on work she did with Giovanelli in the 1980s by carrying out additional observations of individual galaxies that were too faint to show up on the survey. She wants to calculate the mass of a huge connected filament of galaxies they mapped back then, known as the Pisces-Perseus Supercluster, which is made up of tens of thousands of galaxies.
“Mass in the universe includes not just the stars and galaxies that give off light but also dark matter,” she says. “Theory tells us that we should be able to see the effect that the mass contained in dark matter has on the motions of galaxies in a supercluster like Pisces-Perseus. Riccardo [Giovanelli] and I, and our students, tried to detect the pull of dark matter in the 1990s, but we never had enough data to make it work. ALFALFA has been a big step forward in that direction, and with these additional observations by the Undergraduate ALFALFA Team, we should have enough. This would be the first time the mass of a supercluster has ever been measured directly by examining galaxy motions.”
Backyard Telescope Inspires a Lifetime Career
Haynes credits her career as an astronomer and an educator to a moment from her early teens when her older brother borrowed money from her to order a small reflecting telescope. She soon began observing the sky. “I was in the backyard one night observing the rings of Saturn when a police car pulled up,” she remembers. “The neighbor had reported a suspicious person wandering around in the dark. The policemen wanted to know what I was doing, and when I said I was looking at Saturn’s rings, they asked to look, too. They questioned me about what they were seeing, and that’s when I knew this was what I wanted to do. I decided I would become an astronomer. At the time, I had no idea what that would mean, but here I am.”
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