Three brightly pulsating stars fleeing from the Milky Way galaxy have given Rochester Institute of Technology scientists a new method of identifying dark matter and the dwarf galaxies that possess high levels of the elusive matter. Not only that, the method also explains the ripples seen in the outer disk of the galaxy.
The new method is the first application of the field of asteroseismology, which uses waves in the Milky Way's galactic disk to characterize the interior structure and mass of galaxies, much like seismologists analyze waves to study the Earth's interior.
The team used the three fleeing stars as Cepheid variables - stars used to measure distance in galaxies - and calculated their speed using spectroscopic observations. Using these variables, the team was able to use their velocity to confirm previous research that they conducted using Cepheid variables to determine the location of a dark-matter dominated dwarf galaxy.
"The radial velocity of the Cepheid variables is the last piece of evidence that we've been looking for," Sukanya Chakrabarti, who headed the research, said in a press release. "You can immediately conclude that they are not part of our galaxy."
Dark matter particles make up approximately 85 percent of the mass of the universe and our current lack of technologies that can detect and understand the invisible particles is a huge problem in astronomy. The new method devised by Chakrabarti and her team could help scientists locate satellite galaxies that are dominated by dark matter.
"We have made significant progress into this new field of galactoseismology where by you can infer the dark matter content of dwarf galaxies, where they are, as well as properties of the interior of galaxies by looking at observable disturbances in the gas disk," Chakrabarti said.
The study also explored the common notion that old stars make up dark matter halos and young stars make up the gaseous stellar disks.
"Given the evidence, these are very likely young Cepheid variables," Chakrabarti said. "It raises the question, shouldn't we also be exploring and looking for young Cepheid variables in the halo?"
Chakrabarti believes that unknown Cepheid variables originating from a gaseous dwarf galaxy could be making their way into the halo.
"We used to have a static picture of galaxy evolution but now we know that galaxies are constantly merging with other smaller galaxies and so within this more dynamical scenario, it's important to ask why wouldn't there be young Cepheid variables that are made in the halo due to fresh gas flowing in, or due to gas-rich dwarf galaxies merging with our own," Chakrabarti said.
The findings were submitted to Astrophysical Journal Letters on Jan. 7.
Take a look at Chakrabarti presenting her findings on TED Talks below:
