January 17, 2014
Himiko Galaxy’s Space Blob Halo Dates Back To The Cosmic Dawn
redOrbit Staff & Wire Reports - Your Universe Online
Questions surrounding the glowing gaseous halo extending from a massive early galaxy that have puzzled astronomers since its discovery in 2009 have finally been answered by research appearing in a recent edition of The Astrophysical Journal.
At the time Himiko is being observed, the universe was just six percent of its current size and the first stars and galaxies were only beginning to form, the researchers explained. However, scientists were puzzled as to how such an early galaxy would be able to power such as massive, glowing cloud of gas.
As part of the new study, researchers from the California Institute of Technology (Caltech), the University of Tokyo and Harvard-Smithsonian Center for Astrophysics conducted a new analysis of Himiko using the Hubble Space Telescope and the new Atacama Large Millimeter/submillimeter Array (ALMA) in Chile.
“The data collected through these observations answered the initial question about the source of energy powering Himiko, but revealed some puzzling data as well,” Caltech explained in a statement. “The Hubble images, receiving optical and ultraviolet light, reveal three stellar clumps covering a space of 20,000 light-years.”
“Each clump is the size of a typical luminous galaxy dating to the epoch of Himiko,” they added. “Together, the clumps achieve a prodigious rate of star formation, equivalent to about one hundred solar masses per year. This is more than sufficient to explain the existence of Himiko and its gaseous halo.”
According to Richard Ellis, a professor of astronomy at Caltech, the discovery of the three stellar clumps alone is exciting, as it means that Himiko is a rare phenomenon known as a “triple merger.” However, when studying the galaxy using ALMA, the investigators found that even though there were copious amounts of energy at ultraviolet and optical frequencies, it had little submillimeter and radio activity.
“Ordinarily, intense star formation creates dust clouds that are composed of elements such as carbon, oxygen, and silicon, which are heavy in comparison to the hydrogen and helium of the early universe,” the institute said. “When these dust clouds are heated up by the ultraviolet light emitted by the developing stars, the dust reradiates the ultraviolet light out into the universe at radio wavelengths.”
However, ALMA was unable to receive radio signals from Himiko, which led the study authors to believe that there are no heavier elements present in the galaxy. Furthermore, the spectral signature affiliated with gaseous carbon emissions, a common occurrence in galaxies with intense star formation, was also absent.
“Both of these nondetections – of substantial radio waves and of gaseous carbon – are perplexing since carbon is ordinarily rapidly synthesized in young stars,” the institute explained. “Indeed, carbon emission has heretofore been recommended as a tracer of star formation in distant galaxies.”
However, Ellis and his colleagues found that Himiko lacks the heavier element dust clouds typically found in energetic galaxies, and instead is comprised of hydrogen and helium originating from the Big Bang. They came to this conclusion after ruling out multiple other possibilities, ultimately concluding that Himkio is likely a primordial galaxy being observed while forming during the cosmic dawn (400 million to 1 billion years after the Big Bang).
“Astronomers are usually excited when a signal from an object is detected, but in this case it's the absence of a signal from heavy elements that is the most exciting result,” Ellis said. The research was funded through grants from the Space Telescope Science Institute, the World Premier International Research Center Initiative (WPI Initiative) and the Japan Society for the Promotion of Science (JSPS).