UH Hilo’s newest astronomer researches nothing less than the structure of the universe

Kathy Cooksey is young, hip, ambitious and an accomplished scientist—and she’s chosen Hilo as her forever home.

By Susan Enright.

Kathy and her two students flash the shaka with observatories in the background.
Kathy Cooksey (center) atop Maunakea with students Natalie Nagata, a UH Mānoa physics major, and Robert Ponga, a UH Hilo astronomy and physics major. Both students worked on research with Cooksey in July 2014. Photos courtesy of Kathy Cooksey.
Kathy Cooksey in her office, small telescope in background.
Kathy Cooksey

Behind her right shoulder, a colorful tattoo peeks out from Kathy Cooksey’s racerback top. It’s of a Korean-themed landscape inspired by her hanbok or traditional Korean dress. It’s a typical landscape scene of mountains with a sunset—made as the sam saeg-ui taegeuk (Korean “tri-yin-yang”) that symbolizes heaven, earth, and humanity—with flowers and butterflies. It tells so much about Kathy Cooksey: her deep connection to her ancestry, to balance, and to the sky.

She also has a deep connection to what lies beyond the sky.

Cooksey is an astronomer, a newcomer this year to the University of Hawai‘i at Hilo—but don’t let her youthful persona fool you into thinking she’s not already highly accomplished in her field. She researches nothing less than the large-scale gaseous structure in the universe to understand how various elements cycle in and out of galaxies over cosmic time. Her specific area of expertise is the intergalactic medium (IGM), the gas surrounding and between galaxies.

Kathy Cooksey doing a demonstration with school children on the Campus Center Plaza. Boy is holding a wheel suspended on a vertical rod.
Kathy Cooksey does a demonstration with future scientists of Hawaii Island at Elison Onizuka Science Day at UH Hilo, Jan. 2014.

She says she chose Hilo as her home (she and husband Patrik Jonsson have purchased a classic 1950s house in town that they are renovating) because UH Hilo offered a position that allows her to focus on astronomy in teaching via its astronomy major and research via its access to world-class telescopes on Maunakea.

“I never conceived of such a teaching-focus, research-enabling institution when I set out to be an astronomer,” she says. “I thoroughly enjoyed the academic community on my campus interview (at UH Hilo). In addition, Hilo and the Big Island are where I can imagine myself living contentedly for a long, long time. Work-life balance is important to me, and the life Hawai‘i offers is right up my alley—outdoorsy, friendly, relaxed. I didn’t bother applying to places where I didn’t think I could live happily.”

Researching how stars and galaxies formed and evolve

Cooksey is no small catch for UH Hilo. She received her master of science in astronomy and astrophysics and doctor of philosophy in astronomy and astrophysics from University of California at Santa Cruz. And she is now happily settling into her new life at the Hilo university as an assistant professor of astronomy, teaching and doing her research.

“As light from bright, distant objects traverse the universe, intervening gas clouds between, around, and in galaxies absorb the light at wavelengths characteristic, albeit redshifted, of the chemical elements in the clouds,” Cooksey explains about her research. “By identifying and modeling the elements associated with absorption-line systems, we learn about how gas is processed through and dispersed from galaxies.”

A redshift occurs whenever a light source moves away from an observer, an inherent occurrence in astronomical observation. Cooksey and colleagues have conducted the largest surveys for triply ionized carbon at low, intermediate, and high redshift (Cooksey et al. 2010, Cooksey et al. 2013, and Simcoe et al. 2011, respectively, in The Astrophysical Journal).

“This means we study the large-scale gaseous structure and its evolution from today to almost 13 billion years ago,” she explains. “Heavy elements in the large-scale gaseous structure provide top-level constraints on how stars and galaxies formed and evolve and how they are distributed in the universe. We discovered how the triply ionized carbon systems are increasing in number from the past to now. Though we have thousands of systems, they can all be attributed, statistically, to arising in the extended gaseous halos of galaxies.”

Cooksey says her most surprising find is about the gas surrounding galaxies, called the circum-galactic medium or CGM, a relatively new concept in astronomy. There is more and more evidence piling up that this gas is important to how galaxies form and evolve.

“I’m finding it curious what characteristics of the CGM evolve and what do not,” she says. “For example, the size of the CGM traced by triply ionized carbon absorption does not seem to change with time, though galaxies themselves change greatly, in size as well as other properties, over the same time period.”

She says it makes one think there is a “conspiracy” to fix some properties to not evolve though seemingly related properties do evolve.

For her dissertation (she received her doctor of philosophy in 2009), Cooksey analyzed archival Hubble Space Telescope ultraviolet spectra to characterize how the intergalactic medium (IGM) and galaxies relate and how heavy elements like oxygen and carbon are moved from the sites of production in the stars of galaxies to the large-scale gaseous structure (the IGM).

This work led to her becoming a panelist for Hubble proposal reviews, where she served for Cycle 19 (2011), Cycle 21 (2013), and Cycle 22 (2014), on one of two panels broadly classified as extragalactic. “Cycle” refers to each new call for proposals and roughly corresponds to the number of years the Hubble has been operating. The panels peer-review and rank proposals for Hubble resources.

The awarding of observation runs is prestigious in the field of astronomy. Cooksey was awarded three nights with the 8.2-m Subaru Telescope in August 2014, 1.5 nights with the 10-m Keck II Telescope in January 2015, and two nights on the UH88 Telescope to take spectra of distant objects to study the chemical properties of intervening gas.

“Part of understanding (gaseous) systems is to take better data, which the High Dispersion Spectrograph on Subaru enables us to do,” she says. The Subaru Telescope on Maunakea is owned and operated by the National Astronomical Observatory of Japan.

Kathy, her husband Patrik, and two students at Subaru Telescope on Maunakea.
(l-r) Students Robert Ponga and Natalie Nagata, and Kathy and her husband Patrik, at Subaru Telescope on Maunakea, summer 2014.

Engaging her students in applied learning

Robert Ponga, a senior majoring in astronomy and physics at UH Hilo, has been working with Cooksey on the Subaru project since the beginning of summer 2014. Ponga is looking to characterize the highly enriched gas surrounding distant galaxies. In his project titled, “Analysis of Strong Triply Ionized Carbon Systems in Galaxy Halos,” he is using a suite of software programs to model spectral data of unique systems from the group’s large study of Sloan Digital Sky Survey (SDSS) spectra, looking in particular for heavy-element enrichment of the gas.

Previously, Cooksey had done some observations at Las Campanas Observatory in Chile as a National Science Foundation Postdoctoral Fellow at the Massachusetts Institute of Technology, and Ponga analyzed that over the summer as a junior specialist for Xavier Prochaska, an astronomy and astrophysics professor at UC Santa Cruz, under the direct supervision of Cooksey. Ponga is continuing to analyze the old data as a Hawai‘i/NASA Space Grant Consortium Fellow at UH Hilo and also will incorporate the new Subaru observations.

Kathy and two students stand on the catwalk with other observatories in the background.
Kathy Cooksey stands behind two of her students, Natalie Nagata and Robert Ponga, on the catwalk at Subaru Telescope on Maunakea.

“His work is confirming preliminary analysis which suggested these strong triply ionized carbon systems trace very heavy-element-enriched gas,” says Cooksey. “This might help solve an outstanding problem in astronomy where we know how many heavy elements there should be, based on star-formation rates, but we couldn’t find it. It seems like it may have been missing (from the data) because it’s in gaseous structure that’s somewhat tricky to observe. But since our group conducted such a large survey of SDSS, we identified thousands of such systems.”

Cooksey also proposed for time at the UH88 telescope to take spectra of low-redshift quasar candidates to see if they are quasars and to measure their redshifts.

“Quasars are the bright, energetic center of galaxies powered by their supermassive holes,” she explains. “Quasars are the background sources we use to detect foreground gas in absorption. Low-redshift quasars, which are closer to us, are rarer than at high redshift, but the low-redshift quasars enable us to probe the large-scale gaseous structure over the last eight-billion years, which is the majority of cosmic time.” For perspective, she notes the universe is 13.7 billion-years-old.

The Hubble Space Telescope is the only ultraviolet satellite left with ability to study the low-redshift gaseous structure. Cooksey and her research team are searching for more low-redshift quasars so they can follow up with the Hubble observations before it dies. The team observed for half a night on Sept. 22 (the other half lost to technical difficulties).

“Without even processing the data, we could see we detected some quasars,” she says.

In addition to Ponga, Cooksey is working on a number of research projects suitable for undergraduate involvement.

“I am currently working Robert (Ponga), and over the summer, I worked with a UH Mānoa student,” she says. “I participated in a lot of undergraduate research programs myself, and I clearly see the benefit of it. More importantly, the nature of my research means students learn a lot about computers, programming, and statistical techniques.”

She says these are highly transferrable skills and will support the students in a range of professions.

“Astronomy is an exciting subject area and entices students to come and study astronomy at UH Hilo,” she explains. “But for their benefit and for the STEM workforce in general, I actually use the allure of astronomy to teach highly transferable skills such as problem solving (and) programming.”

Outreach and education on equity in the sciences

Cooksey also does a lot of education and outreach programs, including training, and has done so since a young graduate student. Through that work she’s learned a lot about science pedagogy and about diversity and equity in the sciences. This knowledge profoundly affects how she teaches and interacts with her students.

Kathy stands with a large group of young school children in their classroom.
Kathy Cooksey doing community outreach education with kindergarten students at Waikea.

“As a new member to the greater community, I’m seeking ways to share my knowledge of science teaching and issues of diversity and to find people who also care about such things so that I may continue to learn,” she says.

Toward this end, Cooksey will give a public talk, “Is Science a Meritocracy?: Issues of Diversity & Equity,” on Oct. 23 at 7:00 p.m., in room 108 at the UH Hilo Sciences and Technology Building off West Lanikaula Street. She will discuss the “leaky science pipeline,” the gradual attrition of students on the path to a science-related career—most pronounced for certain gender and racial groups. She also will present the demographics of scientists in various fields, and offer researched-based suggestions to combat the adversity.

She hopes the public talk will help her find similarly interested people.

Contact Kathy Cooksey.


About the writer of this story: Susan Enright is a public information specialist for the Office of the Chancellor and editor of UH Hilo Stories. She received her bachelor of arts in English and certificate in women’s studies from UH Hilo.

Share this story