In a new study carried out by astronomers using NSF’s Green Bank Telescope (GBT), W.Va., and data from other ground-based radio telescopes, the dwarf galaxies that orbit closest to the Milky Way’s gravitational sphere of influence appear to be devoid of star-forming hydrogen gas, which has, in turn, stunted their growth.
“After billions of years of interaction, astronomers wondered if the nearby dwarf spheroidal galaxies have all the same star-forming ‘stuff’ that we find in more distant dwarf galaxies,” said astronomer and lead researcher Kristine Spekkens, of the Royal Military College of Canada.
Our galaxy is the largest member of a compact group of galaxies — the Milky Way has a swarm of smaller dwarf galaxies surrounding it. Very close to the Milky Way is a collection of dwarf ‘spheroidals’ that are believed to be the left-over ancient ‘crumbs’ from our galaxy’s early evolution. Further away, irregularly-shaped dwarf galaxies, which are not gravitationally bound to the Milky Way, gather and are thought to be newcomers to the galactic neighborhood.
As discussed in a paper published in the current edition of The Astrophysical Journal Letters, Spekkens’ team spotted a very definite boundary in the star-forming neutral hydrogen gas that should be contained within the surrounding dwarf galaxies. This is the most detailed survey of neutral hydrogen in nearby dwarf galaxies ever carried out.
“What we found is that there is a clear break, a point near our home Galaxy where dwarf galaxies are completely devoid of any traces of neutral atomic hydrogen,” Spekkens said in a National Radio Astronomy Observatory (NRAO) news release.
It appears that, within a distance of 1,000 light-years from the outer edge of our galaxy, the dwarf spheroidal galaxies are rare, but beyond 1,000 light-years, the dwarf irregular galaxies “flourish.”
Read more at Discovery News
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