The assistant professor of astronomy was part of an international team that uncovered two galaxies at the heart of a Lyman-alpha Blob.
Lyman-alpha Blobs (LABs) have been a mystery since their discovery in the '90s. These large clouds of hydrogen gas—one is known to be 10 times larger than the Milky Way galaxy in diameter—shine brightly in outer space, but for decades no one knew why or how.
Desika Narayanan was part of an international team of researchers that recently discovered that, in the case of one such previously well-studied LAB—SSA220 Lyman-alpha Blob 1(LAB-1)—it is actually two young galaxies at the center of the cloud that is undergoing a bout of furious star formation, causing the illumination.
The researchers, who just published their findings in the Astrophysical Journal, used the Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility in northern Chile featuring a collection of 66 radio telescopes that allows for unprecedented sensitivity and resolution, and the European Southern Observatory's Very Large Telescope to study LAB-1. This research could not have been done previously as this very new technology is, says Narayanan, "allowing us to see this well-studied blob in a whole new light, so to speak."
Another thing that makes this research unique is that the observations from ALMA and other telescopes were coupled with theoretical simulations of galaxy formation. Narayanan's contributions, in fact, were the creation of these cosmological simulations. Some of the supercomputing calculations were done on the Fock cluster in Haverford College's Koshland Integrated Natural Sciences Center, with the aid of staff member Joe Cammisa.
"We set up a number of simulations to track the light coming from the central galaxy, and saw it scatter off of the hydrogen surrounding this galaxy," says the Haverford assistant professor of astronomy. "The analogy used is that it's like light coming from a street light and scattering off of fog around it. There's a bright halo of light around the street light, as there is around the galaxies in this Blob."
Narayanan and the team, which was headed up by Jim Geach of the University of Hertfordshire in the U.K., observed that the two galaxies within LAB-1 appear to be an early phase in the formation of a massive cluster of galaxies. Given the distance of LAB-1 from earth, this formation actually happened 12 billion years ago, roughly 2 billion years after the formation of the universe. So, going forward, this research can not only help scientists eventually uncover the origin of these Blobs, but also understand, in a larger context, how galaxies form, grow, and evolve.
"Unveiling the galaxies shrouded in LAB-1 did more than just put to bed the long-standing issue of the gas cloud's glow," says Narayanan. "It provided a rare opportunity to see how young, growing galaxies behaved when the universe was quite young."
