Using the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers have observed a significant amount of cold, neutral gas in the outer regions of A1689-zD1, one of the youngest and most distant galaxies ever found.
This artist’s conception illustrates the previously unknown complexity of the young galaxy A1689-zD1. Image credit: ALMA / ESO / NAOJ / NRAO / B. Saxton, NRAO, AUI & NSF.
A1689-zD1 is located roughly 13 billion light-years away in the constellation of Virgo.
This star-forming galaxy was discovered hiding out behind a galaxy cluster called Abell 1689 in 2007 and confirmed in 2015.
A1689-zD1 is observable only by virtue of its brightness being amplified more than 9 times by a gravitational lens in the form of Abell 1689.
“A1689-zD1 is located in the very early Universe — only 700 million years after the Big Bang,” said lead author Hollis Akins, an undergraduate student Grinnell College.
“This is the era where galaxies were just beginning to form.”
“What we’re seeing 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 did not previously believe applied to these normal galaxies.”
One of these uncommon processes is the galaxy’s production and distribution of star-forming fuel, and potentially a lot of it.
Akins and colleagues used ALMA to home in on a halo of carbon gas that extends far beyond the center of A1689-zD1.
This could be evidence of ongoing star formation in the same region or the result of structural disruptions, such as mergers or outflows, in the earliest stages of the galaxy’s formation. According to the team, this is unusual for early galaxies.
“The carbon gas we observed in this galaxy is typically found in the same regions as neutral hydrogen gas, which is also where new stars tend to form,” Akins said.
“If that is the case with A1689-zD1, the galaxy is likely much larger than previously thought.”
“It’s also possible that this halo is a remnant of previous galactic activity, like mergers that exerted complex gravitational forces on the galaxy leading to the ejection of a lot of neutral gas out to these large distances.”
“In either case, the early evolution of this galaxy was likely active and dynamic, and we’re learning that this may be a common, although previously unobserved, theme in early galaxy formation.”
This spectacular view from the Hubble Space Telescope shows the galaxy cluster Abell 1689. The galaxy A1689-zD1 is located in the box, although it is still so faint that it is barely seen in this picture. Image credit: NASA / ESA / L. Bradley, Johns Hopkins University / R. Bouwens, University of California, Santa Cruz /H. Ford, Johns Hopkins University / G. Illingworth, University of California, Santa Cruz.
The astronomers also observed outflows of hot, ionized gas — commonly caused by violent galactic activity like supernovae — pushing outward from the center of A1689-zD1.
It’s possible, given their potentially explosive nature, that the outflows have something to do with the carbon halo.
“Outflows occur as a result of violent activity, such as the explosion of supernovae (which blast nearby gaseous material out of the galaxy) or black holes in the centers of galaxies (which have strong magnetic effects that can eject material in powerful jets),” Akins said.
“Because of this, there’s a strong possibility that the hot outflows have something to do with the presence of the cold carbon halo.”
“And that further highlights the importance of the multiphase, or hot to cold, nature of the outflowing gas.”
The results appear today in the Astrophysical Journal.
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Akins et al. 2022. ALMA reveals extended cool gas and hot ionized out in a typical star-forming galaxy at z = 7.13. ApJ, in press;
Source link: https://www.sci.news/astronomy/bigger-early-galaxies-10902.html
