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Astronomers Discover New Dwarf Galaxy, Possible New Protogalaxy

January 12, 2013

redOrbit Staff & Wire Reports — Your Universe Online

Through detailed study of the constellation Ursa Major, astronomers have reportedly found two new clouds of hydrogen gas, one which is a faint dwarf galaxy, and the other which could be a proto dwarf galaxy that has not yet had a chance to form any stars.

The research team, led by Case Western Reserve University astronomy professor Chris Mihos, have dubbed the gas clouds — which are formally named G1425+5235 and G1355+5439 — Skipper and Gilligan, characters from the popular old television show Gilligan´s Island.

They were discovered in the M101 group of galaxies, and are fully reported in a pair of papers that have been published in the latest edition of the Astrophysical Journal.

Both galaxies are independent from M101 itself, the university confirmed in a statement Friday. In discovering Skipper and Gilligan, Mihos and his colleagues had to “discern starlight 100 times fainter than the black of the dark night sky and trace extremely low concentrations of interstellar gases among the celestial bodies.”

Following their discovery, both gas clouds were further analyzed using images provided by the Sloan Digital Sky Survey in New Mexico. Faint patches of starlight were detected in Skipper, thus confirming that it is indeed a true dwarf galaxy that is populated by both gas and stars. However, no such starlight was found inside of Gilligan, leading Mihos to surmise it could be a proto dwarf galaxy.

“We´ll follow up,” the professor, whose research was funded in part by grants from the National Science Foundation, said. “There´s a gas cloud but no stars yet. People have seen a few starless clouds before, but they´ve always associated with gas from a larger galaxy. This is different — it has nothing to link it to the other galaxies in the group. It may be one of the first true protogalaxies ever discovered.

“We created the deepest image ever taken of M101 and followed it up with the most sensitive survey of gas clouds surrounding the galaxy,” added Mihos, who is credited as the lead author on both recently published studies. “Compared to what is seen in the Hubble Space Telescope image, the galaxy´s disk is much larger and we can see very large, faint plumes of stars and streamers of gas in its outskirts.”

The researchers first used the Burrell Schmidt wide field telescope at Kitt Peak National Observatory in Arizona to complete their optical survey, then used the Robert C. Byrd Green Bank Telescope at the National Radio Astronomy Observatory in West Virginia to seek out neutral hydrogen gas, which is used as fuel for forming galaxies and stars, around M101.

They hope to use the Very Large Array telescope at the National Radio Astronomical Observatory in New Mexico in the near future for further analysis of Gilligan. Specifically, they are looking to test whether or not it truly is a protogalaxy by mapping out the gas in greater detail, comparing it to existing known dwarf galaxies, and determining whether or not it is getting set to form stars.

Source: redOrbit Staff & Wire Reports – Your Universe Online