The discovery of the faintest known galaxies outside the Milky Way could help scientists develop global models of how the oldest galaxies in the universe formed, according to findings announced Jan. 11 at the 241st meeting of the American Astronomical Society.
A team of researchers led by Burçin Mutlu-Pakdil, now an assistant professor of physics and astronomy at Dartmouth College, has identified three very faint dwarf galaxies (UFDs) that are among the faintest detected outside the Local Group, a galaxy cluster that includes the Milky Way and Andromeda. .
Located about 11.4 million light-years from Earth, the researchers report that the galaxies are 12 billion years old, and almost all of their stars formed in the early universe. Astrophysical Journal.
The galaxies are the first UFDs to be found around a spiral galaxy with a mass of the Milky Way, orbiting a galaxy known as NGC253, or the Sculptor Galaxy. However, their properties are consistent with UFDs within the local group, which can help scientists develop more accurate models of UFDs in general. Most of the known examples of UFDs are within the local group, but different environments could influence their formation and evolution, Mutlu-Pakdil said.
“Our work is a necessary first step toward further understanding of weak galaxies outside the Local Group, and toward constraining the demographics of ultralight dwarf galaxies,” Mutlu Pakdel said. “We still don’t know if the local group UFD is typical or unusual. To answer this fundamental question, we need to discover more UFDs outside of our local environment and study them in detail.”
UFDs are the least known and least chemically evolved galaxies. However, dark matter is most dominated by it, the mysterious form of matter thought to make up most of the universe. For these reasons, astronomers consider UFDs to be primordial fossils of the early universe that could provide the best opportunities for studying the formation of the universe and the formation of its first galaxies.
“Dwarf galaxies are the building blocks of larger galaxies,” Mutlu Pakdel said. “UFDs are the best place to study galaxy formation on the smallest scales and see how the smallest clumps of dark matter are filled with stars and turn into galaxies.”
The paper, “Hubble Space Telescope Observations of NGC 253 Dwarf Satellite: Three Very Faint Dwarf Galaxies” is published by Astrophysical Journal. This study was conducted as part of the Panoramic Centaur and Sculptor Imaging Survey (PISCeS) project, a Magellan + Megacam survey that aims to find new faint satellite galaxies, including UFDs.
Burçin Mutlu-Pakdil et al, Hubble Space Telescope observations of the NGC 253 dwarf satellite: three very faint dwarf galaxies*, Astrophysical Journal (2022). DOI: 10.3847/1538-4357/ac4418
Provided by Dartmouth College
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