The first galaxies are not as small as they seem


Observations with the ALMA telescope in Chile have provided evidence that early galaxies may be larger and more complex than previously thought, reaching their ‘of age’.

The investigation, presented at the 240th meeting of the American Astronomical Society (AAS), detected a significant amount of cold neutral gas in the outer regions of the young galaxy A1689-zD1, as well as hot gas emerging from the center of the galaxy. The results will be published in an upcoming issue of The Astrophysical Journal (ApJ).

A1689-zD1, a young active star-forming galaxy slightly dimmer and less massive than the Milky Way, lies about 13 billion light-years away in the constellation Virgo cluster. It was discovered hidden behind the galaxy cluster Abell 1689 in 2007 and confirmed in 2015 through gravitational lensing, which amplified the brightness of the young galaxy more than 9 times.

Since then, scientists have continued to study the galaxy as a possible analogue of the evolution of other “normal” galaxies. This label, normal, is an important distinction that has helped researchers divide the behaviors and characteristics of A1689-zD1 into two groups: typical and rare, with rare characteristics that mimic those of later, more massive galaxies.

“A1689-zD1 is found in the early Universe, just 700 million years after the Big Bang. This is when galaxies were just beginning to form.”Hollis Akins, an undergraduate student in astronomy at Grinnell College and senior author of the research, said. it is a statement. “What we see in these new observations is evidence of processes that may contribute to the evolution of what we call normal galaxies as opposed to massive galaxies. More importantly, These processes are ones we didn’t previously think applied to these normal galaxies.”

One of these unusual processes is the production and distribution of star-forming fuel in the galaxy, and potentially in large quantities. The team used ALMA’s highly sensitive Band 6 receiver to locate a halo of carbon dioxide that extends far beyond the center of the young galaxy. This could be evidence of continued star formation in the same region or the result of structural changes, such as mergers or exits, in the early stages of galaxy formation.

According to Akins, this is unusual for early galaxies. “The carbon dioxide we observe in this galaxy is generally found in the same regions as neutral hydrogen gas, which is also where new stars tend to form. If this is the case with A1689-zD1 , the galaxy is likely to be much larger than before.It’s also possible that this halo is a remnant of earlier galactic activity, such as mergers that exerted complex gravitational forces on the galaxy that led to the expulsion of a large amount of neutral gas at these great distances. The early evolution of this galaxy was probably active and dynamic, And we’re learning that this may be a common, though never-before-seen, theme in the formation of early galaxies.”

More than unusual, the discovery could have important implications for the study of galactic evolution, especially when radio observations reveal details not visible at optical wavelengths.

Seiji Fujimoto, postdoctoral researcher at the Cosmic Dawn Center of the Niels Bohr Institute and co-author of the research, said: “The emission of carbon dioxide in A1689-zD1 is much larger than what was observed with the telescope. Hubble space, and this could mean that the first galaxies are not as small as they seem If in fact the first galaxies are larger than previously believed, it would have a huge impact on the theory of galaxy formation and evolution in the early Universe.”

Led by Akins, the team also observed outflows of hot ionized gases, usually caused by violent galactic activity such as supernovae, pushing outward from the center of the galaxy. It is possible, given their potentially explosive nature, that the outlets have something to do with the carbon halo..

“Outflows occur as a result of violent activity, such as supernova explosions, which knock nearby gaseous material out of the galaxy, or black holes at the center of galaxies, which have strong magnetic effects that can eject material in powerful jets. For this reason, there is a strong possibility that the hot fluxes have something to do with the presence of the cold carbon halo,” Akins said. “And that again highlights the importance of the multiphase, or hot-cold, nature of the gas leaving.”

Darach Watson, associate professor at the Cosmic Dawn Center at the Niels Bohr Institute and co-author of the new research, confirmed that A1689-zD1 was a high redshift galaxy in 2015, making it the most distant known dusty galaxy.

“We’ve seen this type of extended gas halo emission from galaxies that formed later in the Universe, but seeing it in such an old galaxy means this type of behavior is universal.” even in the smallest galaxies that formed most of the stars in the Universe. primitive universe. Understanding how these processes occurred in such a young galaxy is essential to understanding how star formation occurred in the early Universe.”

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