ALMA | NRAO | 2017 Mar 23
By harnessing the extreme sensitivity of the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers have directly observed a pair of Milky Way-like galaxies seen when the universe was only eight percent of its current age. These progenitors of today’s giant spiral galaxies are surrounded by "super halos" of hydrogen gas that extend many tens of thousands of light-years beyond their dusty, star-filled disks.
Astronomers initially detected these galaxies by studying the intense light from even-more-distant quasars. As this light travels through an intervening galaxy on its way to Earth, it can pick up the unique spectral signature from the galaxy’s gas. This technique, however, normally prevents astronomers from seeing the actual light emitted by the galaxy, which is overwhelmed by the much brighter emission from the background quasar. ...
With ALMA, the astronomers were finally able to observe the natural millimeter-wavelength "glow" emitted by ionized carbon in the dense and dusty star-forming regions of the galaxies. This carbon signature, however, is considerably offset from the gas first detected by quasar absorption. This extreme separation indicates that the galaxies’ gas content extends well beyond their star-filled disks, suggesting that each galaxy is embedded in a monstrous halo of hydrogen gas. ...
Astronomers Observe Early Stages of Milky Way-like Galaxies in Distant Universe
University of California, Santa Cruz | 2017 Mar 23
New observations reveal massive, dusty galaxies with high rates of star formation and large, extended layers of gas
158-μm emission from the host galaxies of damped Lyman-alpha systems - Marcel Neeleman et al
- Science 355(6331):1285 (24 Mar 2017) DOI: 10.1126/science.aal1737