Dwarf Galaxies’ Existence Explained

A study published in July by a Harvard-Smithsonian Center postdoctoral student has uncovered important clues about the disputed explanation for dwarf galaxies beyond the gravitational effects of the Local Group, a group of more than twenty galaxies including the Milky Way.

In the study, entitled ‘Resonant stripping as the origin of dwarf spheroidal galaxies,’ Elena D’Onghia explained the existence of dwarf galaxies on the outskirts of the Local Group, and found that slightly lower mass galaxies seemed to rotate around slightly larger galaxies which in turn stripped the smaller galaxies of their luminous matter. She coined this process “resonant stripping.”

These “ultra-faint” dwarf galaxies, which lack stars and gas and are mainly composed of dark matter, were previously thought to be accredit only by galaxy-galaxy harassment, in which one large galaxy such as the Milky Way stripped a much smaller galaxy of its luminous matter.

Gurtina Besla, a Ph.D. candidate at the Harvard-Smithsonian Center for Astrophysics and D’Onghia’s co-researcher, explained that this study took a new perspective by looking at the interaction of galaxies that have similar masses.

“[This study] shows the importance of difference scales and thinking of small group environment [and] the interactions of these small things,” she said.

She added that it marked the “next stage of modifying our thinking” about the formation of the universe.

Previous studies did not look at the relationship between two similar sized galaxies, rather only the relationship between large galaxies and dwarf galaxies because that is how the majority of the universe is composed today.

According to Lars E. Hernquist, professor of astrophysics and another co-researcher, D’Onghia’s findings are important because they uncover specific properties about the formation of galaxies. With her findings, astronomers have another clue as to how galaxies interacted in the younger universe. He explained that this information can help eventually explain how lighter galaxies, such as the Milky Way, were formed.