Scientists have mapped the motions of stars within the Milky Way's companion galaxy, the Large Magellanic Cloud, revealing new clues about barred galaxies.
The findings could offer new insight into the processes that shape and form the structures of these galaxies, which contain bar-like bands of stars, researchers report in a new study. Located about 163,000 light-years from Earth, the Large Magellanic Cloud (LMC) — a satellite dwarf galaxy of the Milky Way — is among the closest galaxies to Earth and is visible to the naked eye as a faint cloud in the Southern Hemisphere sky. The LMC is considered an irregular galaxy, given its single spiral arm and stellar bar structure, which is offset from the galaxy's center.
Stellar bar structures are a common feature in spiral galaxies. Scientists think these structures form when small perturbations within the stellar disk strip stars from their circular motions and push them into elongated orbits.. "A specific type of these orbits are the ones that are aligned with the major axis of the bar," lead author Florian Niederhofer, a researcher at the Leibniz Institute for Astrophysics Potsdam, said in a statement. "These are considered to be the 'backbone' of stellar bars and provide the main support of the bar structure."
Using the European's Southern Observatory's (ESO) ground-based Visible and Infrared Survey Telescope for Astronomy (VISTA) in Chile, the researchers studied the motions of stars and their elongated orbits within the LMC. The LMC harbors a variety of stars, ranging from as old as the universe to recently formed, and its close proximity to Earth makes it the perfect candidate for observing the motions of these stars, the researchers said in the statement.
VISTA is designed to survey the southern sky at near-infrared wavelengths. Using these data, the researchers created detailed velocity maps of the galaxy's internal structure, revealing elongated stellar motions that follow the structure and orientation of the galaxy's stellar bar, according to the statement.
"The stunning level of detail in velocity maps shows how much our method has improved, compared with early measurements some years ago," study co-author Thomas Schmidt, a doctoral student at the Leibniz Institute for Astrophysics Potsdam, said in the statement.
VISTA can study individual stars within the LMC and, in turn, the processes that shape and form galaxies and their stellar bar structures. The telescope offers a better understanding of stellar dynamics by observing the same stars multiple times over several years in order to measure the stars' proper motion. The study relied on images collected over nine years to discern the minute motion of the stars as observed by the ground-based telescope.
Measurements of the proper motions of stars are needed to determine the full three-dimensional velocities of the stars. However, until now, only one-dimensional line-of-sight stellar velocities were available by measuring spectroscopic Doppler shifts, or changes observed in the light emitted by a star depending on whether it is approaching or moving away from Earth, according to the statement.
"Our discovery provides an important contribution to the study of dynamical properties of barred galaxies, since the Magellanic Clouds are at present the only galaxies where such motions can be investigated using stellar proper motions," Niederhofer said in the statement. "For more distant galaxies, this is still beyond our technical capabilities."
The findings were published March 29 in the journal Monthly Notices of the Royal Astronomical Society.