Like distant beacons shining through fog, super-bright quasars give astronomers a powerful tool for studying the evolution of galaxies since the universe was a fraction of its current age.
Using a technique known as quasar absorption line spectroscopy, scientists can analyze the clouds of gases in galaxies between the Earth and a faraway quasar - in essence, taking a "core sample" of the universe through time and space, says New Mexico State University astronomer Chris Churchill.
Because the universe is expanding, and the light from extremely distant objects can take millions or even billions of years to reach the Earth, "the further out a galaxy is, the earlier it is in the evolution of the universe," Churchill said. "We can now study galaxies that are almost 10 billion light years away, and that means we can get back to where the universe was only about 10 percent of its current age."
It's a fairly new but active field of research. When 110 scientists from throughout the world gathered in Shanghai, China, March 14-18 to share the latest advances in the field, Churchill and two New Mexico State doctoral students played prominent roles. "Probing Galaxies Through Quasar Absorption Lines" was the name of the conference, sponsored by the International Astronomical Union, the Shanghai Astronomical Observatory and the Chinese Academy of Sciences.
Churchill was invited to present a review of current knowledge on the gas clouds in early epoch galaxies, using the orbiting Hubble Space Telescope and the world's largest ground-based telescope, the Keck 10-meter telescope in Hawaii, to gather high-resolution spectra of light from distant quasars.
As the light from a quasar intersects with the gas cloud of a galaxy, a distinct "fingerprint" is created, Churchill said. The term "quasar absorption line" refers to the absorption of part of the light spectrum as the quasar's light passes through the gas. Every chemical element present in the gas absorbs light in a unique way, so astronomers using this technique can learn the composition of the gas, compare the gases in different types of galaxies, and compare distant galaxies with closer ones.
Brandon Lawton, one of Churchill's Ph.D. students, uses quasar absorption lines to search for organic molecules - the building blocks of life - in other galaxies. He has analyzed six distant galaxies so far without finding organic molecules at the level seen in the Milky Way.
While Lawton's research is young and his sample still small, an ultimate finding that organic material is rare in the universe would be as significant as finding that it is plentiful, Churchill noted. "Maybe our Milky Way is special, like an organic soup," he said.
Lawton presented a poster on his research at the international conference in Shanghai. His research is funded in part by NASA's Origins Program, which is aimed at finding conditions favorable to life in the universe.
Assisting with this line of research is Claudia Santiago, an NMSU junior majoring in physics. She is participating in the Ronald E. McNair Post-Baccalaureate Achievement Program at NMSU, which helps first-generation college students prepare for graduate school.
Glenn Kacprzak, another Ph.D. student who works with Churchill, was invited to present a talk to the international gathering about his research, which focuses on the faint haloes of gas that surround galaxies. His findings reveal that the gas haloes rotate with the galaxies, indicating that they evolved together as a sort of ecosystem.
Kacprzak also has detected perturbations in the gas clouds, suggesting that nearby galaxies "harass each other," creating chimney-like disturbances in the gas clouds. The environment in these clouds affects the formation of new stars and the evolution of the galaxies.
"We're seeing how galaxies evolved and providing hard data for the theorists to constrain our models of how the universe has changed over 10 billion years," Kacprzak said.
Churchill said he tries hard to make opportunities for his graduate students to participate in conferences like the one in Shanghai. "You can read the scientific literature, but it takes on a different dimension if you go to conferences and meet the people who are doing the research and hear them talk about it," he said. "It also helps to instill a sense of confidence and connectivity in the students to participate at this level."
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