UK Physics and Astronomy Team Reveals Evidence of Impacts That Structured the Milky Way Galaxy

LEXINGTON, Ky. (July 17, 2017) — A team from the University of Kentucky’s Department of Physics and Astronomy has observed evidence of ancient impacts that are thought to have shaped and structured our Milky Way galaxy.

Deborah Ferguson, a 2016 UK graduate, is the lead author on a paper that published this week in the Astrophysical Journal (ApJ). Ferguson conducted the research as an undergraduate student with co-authors Susan Gardner, a professor of physics and astronomy in the UK College of Arts and Sciences, and Brian Yanny, a staff scientist and astrophysicist in the Fermilab Center for Particle Astrophysics.

Their paper, “Milky Way Tomography with K and M Dwarf Stars: the Vertical Structure of the Galactic Disk,” presents observational evidence of asymmetric ripples in the stellar disk of our galaxy, which had long been thought to be smooth. Using observations from the Sloan Digital Sky Survey (SDSS) telescope in New Mexico, Ferguson, Gardner and Yanny analyzed the spatial distribution of 3.6 million stars and found ripples that confirm previous work of the senior co-authors. These results can be interpreted as evidence of the Milky Way’s ancient impacts, which could include an impact with the massive Sagittarius dwarf galaxy some 0.85 billion years ago.

“These impacts are thought to have been the ‘architects’ of the Milky Way’s central bar and spiral arms,” Gardner said. “Just as the ripples on the surface of a smooth lake suggest the passing of a distant speed boat, we search for departures from the symmetries we would expect in the distributions of the stars to find evidence of ancient impacts. We have found extensive evidence for the breaking of all these symmetries and thus build the case for the role of ancient impacts in forming the structure of our Milky Way.”

This new paper continues Gardner’s earlier studies with Yanny and others of the breaking of north/south symmetry in the stellar disk of the Milky Way. Their earlier work…

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