Early galaxies may be bigger and more complex than we thought

Scientists used the Atacama Large Millimeter/Submillimeter Array (ALMA) to observe a significant amount of cold neutral gas in the outer regions of the young galaxy A1689-zD1, as well as streams of hot gas from the center of the galaxy.

These results may shed light on a critical phase of galactic evolution for early galaxies, when young galaxies begin to transform to look more and more like their new, more structured cousins.

The observations were presented at a press conference at the 240th meeting of the American Astronomical Society in Pasadena, California, and will be published in the next issue of the journal Astrophysical Journal.

A1689-zD1 is a young active star-forming galaxy. Slightly less bright and less massive than the Milky Way, it is located about 13 billion light-years from Earth in the direction of the constellation Virgo.

Was opened hidden behind the galaxy cluster Abell 1689 in 2007 and confirmed in 2015 due to gravitational lensing, which increased the brightness of the young galaxy by more than 9 times.

Since then, scientists have continued to study the galaxy as a possible analogue evolution of other “normal” galaxies.

This label is ordinary is an important distinction that has helped researchers divide the behavior and characteristics of A1689-zD1 into two groups: typical and unusual, with the unusual characteristics mimicking those of newer and more massive galaxies.

“A1689-zD1 is in the early universe. – just 700 million years after the Big Bang. This is the era when galaxies were just beginning to form,” he said. Hollis Akinsundergraduate student in astronomy at Grinnell College and lead author of the study.

“What we see in these observations is evidence of processes that may contribute to the evolution of what we call normal galaxies, unlike massive galaxies. Most importantly, these processes are processes that we previously thought did not apply to these ordinary galaxies.”

One of these unusual processes is the production and distribution in the galaxy fuel for star formationpotentially in large quantities.

The team used the highly sensitive Band 6 ALMA receptor to observe a halo of carbon gas that extends far beyond the center of the young galaxy.

This may be evidence of ongoing star formation in the same region, or the result of structural disturbances such as mergers or outflows during earlier stages of galaxy formation.

This is unusual for early galaxies, Akins says. “The carbon gas that we have observed in this galaxy is usually found in the same regions as neutral hydrogen gas, where new stars also tend to form. If this is true for A1689-zD1, the galaxy is likely much larger than previously thought.”

“It is also possible that this halo is remnant of galactic activity earlier, such as mergers that impacted the galaxy with complex gravitational forces, which led to the release of large amounts of neutral gas over these large distances, ”adds the astronomer.

“In both cases, the early evolution of this galaxy was probably active, dynamic and we learn that this can be a common themealthough not previously observed during the formation of the first galaxies,” concludes Akins.

This discovery may not just be unusual, it could have significant implications for the study of galactic evolution, especially as radio observations unravel invisible details at optical wavelengths.

Seiji FujimotoA researcher at the Niels Bohr Institute’s Space Dawn Center, who co-authored the study, said: “The carbon dioxide emissions of A1689-zD1 are much more extensive than those observed with the Hubble Space Telescope, which could mean that the first galaxies are not as small as they seem. “.

“If in fact the first galaxies are larger than we previously thought, this great influence on the theory the formation and evolution of galaxies in the early universe,” adds Fujimoto.

Led by Akins, the team also observed bursts of hot ionized gas, often triggered by violent galactic activity such as supernovae, that were being pushed outwards from the center of the galaxy. Given its potentially explosive nature, flows may have something to do with the carbon halo.

“Flows arise as result of violencesuch as supernova explosions, which eject nearby gaseous material from the galaxy — or black holes at the centers of galaxies — which have a strong magnetic effect that can eject material in powerful jets,” Akins said.

“Because of this, there is a strong possibility that warm flows are somehow related to the presence of a cold carbon halo. And it’s rfurther emphasizes the importance multi-phase, or hot to cold, nature of the gas flow,” he added.

Darah Watson, Associate professor at the Niels Bohr Institute’s Cosmic Dawn Center and co-author of the new study confirmed that A1689-zD1 is a high-redshift galaxy in 2015, the most distant known dusty galaxy.

“We have seen this type of large burst of gaseous halos from galaxies that formed later in the universe, but seeing it in such an early galaxy means that this behavior universal even in the humblest galaxies from which most of the stars in the early universe formed,” Watson said.

“Understanding how these processes occurred in such a young galaxy is critical to understand how star formation occurs in the early universe,” the astronomer added.

Kirsten Knudsenprofessor of astrophysics in the Department of Space, Earth and Environment at Chalmers University of Technology and co-author of the study, in 2017 found evidence for the existence of the dust continuum A1689-zD1. Knudsen emphasized the random role of extreme gravitational lensing in making every possible discovery in the investigation.

“Given that A1689-zD1 is more than nine times magnified, we can see important details that are otherwise difficult to see with conventional observations of galaxies so far away. In the end, we see here that the first galaxies Universes are very complex, and this galaxy will set new tasks and research results for some time to come,” the researcher said.

Doctor. Joe Pesce, ALMA Program Manager at the National Science Foundation, added: “This exciting ALMA study adds to a growing set of results indicating that things in the early universe are not exactly what we expected, but are nonetheless really interesting and exciting. !”

Spectroscopic and infrared observations of A1689-zD1 are scheduled for January 2023 using the NIRSpec IFU (Integral Field Unit) and NIRCam instruments on the James Webb Space Telescope.

The new observations will complement previous Hubble and ALMA data, providing a deeper and more complete multiwavelength look at the young galaxy.