Astronomers observe early stages of Milky Way-like galaxies in distant universe

[Binary_Bark]

Artist impression of a progenitor of Milky Way-like galaxies in the early universe with a background quasar shining through a 'super halo' of hydrogen gas surrounding the galaxy. New ALMA observations of two such galaxies reveal that these vast halos extend well beyond the galaxies' dusty, star-forming disks. The galaxies were initially found by the absorption of background quasar light passing through the galaxies. ALMA was able to image the ionized carbon in the galaxies' disks, revealing crucial details about their structures. Credit: A. Angelich (NRAO/AUI/NSF)​

For decades, astronomers have found distant galaxies by detecting the characteristic way their gas absorbs light from a bright quasar in the background. But efforts to observe the light emitted by these same galaxies have mostly been unsuccessful. Now, a team of astronomers using the Atacama Large Millimeter Array (ALMA) in Chile has observed emissions from two distant galaxies initially detected by their quasar absorption signatures, and the results were not what they had expected.
For one thing, emissions driven by star-formation in the galaxies were separated by a surprising distance from the dense gas revealed by quasar absorption, indicating that the galaxies are embedded in an extended halo of hydrogen gas. The estimated star formation rates were also unexpectedly high.
"We had expected we would see faint emissions right on top of the quasar, and instead we saw bright galaxies at large separations from the quasar," said J. Xavier Prochaska, professor of astronomy and astrophysics at UC Santa Cruz and coauthor of a paper on the new findings published March 24 in Science.

More at: https://phys.org/news/2017-03-astronomers-early-stages-milky-way-like.html#jCp