Recently, Astronomers have detected vestigial matter left over from the Big Bang: cold streams of primordial hydrogen powering a distant star-forming galaxy in the early universe. The profuse flow of gas is believed to be crucial for explaining the state of the universe 10 billion years ago, when galaxies were madly forming stars. This discovery was made by a team led by Neil Crighton of the Max Planck Institute for Astronomy and Swinburne university, who made use of a cosmic coincidence: a bright, distant quasar that acted as a “cosmic lighthouse” which illuminated the gas flow from behind.
Systematic survey of absorption systems is made with observations by the Large Binocular Telescope and data taken from the W.M. Keck Observatory’s HIRES echelle spectrograph installed on the 10 meter Keck I telescope on the summit of Mauna Kea, Hawaii. The foreground galaxy was discovered by Charles Steidel, Gwen Rudie (from California Institute of Technology) and collaborators using the Keck Observatory’s LRIS spectrograph on the same telescope.
Current, cosmologists believe galaxies like our Milky Way were formed from a vast reservoir of pristine hydrogen in the intergalactic medium, which permeates the vast expanses between galaxies. Ten billion years ago, when the Universe was one-fifth it’s current age, early proto-galaxies were in a state of constant extreme activity: they were forming new stars at nearly one-hundred times their current rate. This rate of star-forming required a steady source of cosmic fuel. Simulations recently been able to shown how galaxies are formed and fed: gas funnels onto galaxies along thin“cold streams” which, like streams of snow melt feeding a mountain lake, channel cool gas from the surrounding intergalactic medium onto galaxies, continuously topping up their supplies of raw material for star formation.
The researchers have taken advantage of Quasars, the most luminous objects in the universe, which are powered by the infall of matter into a supermassive black hole. By finding that rare case in which the primordial gas near a foreground galaxy is aligned with a quasar, the light from this quasar can be observed passing through the primordial gas. This provides astronomers with a specific set of absorption lines, from which they can determine the chemical composition, density and temperature of the gas.
From this, the team of astronomers led by Neil Crighton has found the best evidence to date for a flow of pristine intergalactic gas onto a galaxy. The galaxy, Q1442-MD50, is so distant that it took 11 billion years for its light to reach us. The primordial gas resides just 190000 light years from the galaxy.
The discovery of this system is part of a larger survey for quasar sightlines which pass near galaxies, which is coordinated by Joseph Heenawi, the leader of the ENIGMA research group at the Max Planck Institute for Astronomy.’
Avishai Dekel (Hebrew University, Jerusalem) was instrumental in theoretically and numerically establishing the current model of cold-flow accretion onto galaxies. While he was not involved on this research, he commented on the results. “This is a very interesting finding,” Dekel said. “It is consistent with the theoretical prediction, based both on galaxies by cold streams from the cosmic web. The low metallicity makes this case for inflow more convincing that earlier detections.”
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