To come into being, galaxies need cold gas to undergo gravity. The larger the galaxy, the more cold gas it needs to fuse and grow.
Massive galaxies found in the early universe were in dire need of storage – cold molecular gases up to 100 billion times the mass of our sun.
But where did these early, super-sized galaxies get so much cold gas when they were penetrated by a warmer environment?
In a new study, astronomers led by the University of Iowa report direct, observational evidence of cold gas currents that they believe provided these early, massive galaxies. They detected cold gas pipelines that cut through the warm atmosphere in the dark matter halo of an early massive galaxy, and provided the material for the galaxy to form stars.
About two decades ago, physicists working with simulations theorized that cosmic filaments during the early universe fed cold gas and embryonic, nodular galaxies to a dark matter halo, where they all collapsed to form massive galaxies. The theory assumed that the filaments should be narrow and densely filled with cold gas to prevent it from being peeled off by the warmer atmosphere.
But the theory had no direct evidence. In this study, scientists studied a gaseous region around a massive galaxy formed when the universe was about 2.5 billion years old, or just 20% of its current age. The galaxy had not been studied before, and it took the team five years to determine its exact location and distance (through its redshift). The team needed a specially equipped observatory, the Atacama Large Millimeter / Submillimeter Array, because the environment of the target system is so dusty that it can only be seen in the submillimeter range of the electromagnetic spectrum.
“This is the prototype, the first case where we detect a halo-scale current that feeds a very massive galaxy,” said Hai Fu, an associate professor in the Department of Physics and Astronomy in Iowa, and the principal and author. of the study. “Based on our observations, such currents can fill the reservoir within about a billion years, which is much shorter than the time the galaxy was available in the period we observed.”
Most importantly, the researchers detected two background quasars being projected at close range from the target system, just as the motion of Jupiter and Saturn drew them closer together when they were seen from Earth during the Great Conjunction last December. Due to this unique configuration, the quasars’ light penetrating through the halogas of the front galaxy left chemical ‘fingerprints’ that confirmed the existence of a narrow stream of cold gas.
These chemical fingerprints have shown that the gas in the streams has a low concentration of heavy elements such as aluminum, carbon, iron and magnesium. Since these elements are formed when the star is still shining and are released into the surrounding medium when the star dies, the researchers determined that the cold gas streams should flow in from outside rather than expel them from the star-galaxy itself.
“Among the 70,000 galaxies in our survey, it is the only one associated with two quasars that are both close enough to investigate the halogas. Even more: both quasars are projected on the same side of the galaxy so that their light can be blocked at two different angular distances by the same current. Fu says. “I therefore feel very happy that nature has given us the opportunity to find this main artery that leads to the heart of a phenomenal galaxy during his adolescence.”
The study, “A long stream of metal-poor cool cool gas around a massive asteroid galaxy at Z = 2.67,” is online in the Astrophysical Journal 24 February.
Study co-authors include Rui Xue, who was a postdoctoral researcher at Iowa and is now a software engineer at the National Radio Astronomical Observatory; Jason Prochaska of the University of California, Santa Cruz; Alan Stockton of the University of Hawaii-Honolulu; Sam Ponnada, who graduated from Iowa last May and is a graduate student at the California Institute of Technology; Marie Wingyee Lau, of the University of California, Riverside; Asantha Cooray, of the University of California, Irvine; and Desika Narayanan, of the University of Florida.
The U.S. National Science Foundation funded the research.