Bachelor researcher captures ‘growing up’ of young galaxies and finds evidence early galaxies may be larger and more complex than we T
Press release from: National Radio Astronomy Observatory
Posted: Wednesday 15th June 2022
Scientists have found a significant amount of cold, neutral gas in the young galaxy’s outer regions using the Atacama Large Millimeter/submillimeter Array (ALMA), an international observatory that cooperates with the US National Science Foundation’s National Radio Astronomy Observatory (NRAO). observes A1689-zD1 and outflows of hot gas from the center of the galaxy. These results could shed light on a critical stage in galactic evolution for early galaxies, where young galaxies begin transforming to become increasingly similar to their later, more structured relatives. The observations were presented today in a press conference at the 240th meeting of the American Astronomical Society (AAS) in Pasadena, California, and will be published in an upcoming issue of the Astrophysical Journal (ApJ).
A1689-zD1 — a young, active, star-forming galaxy that is slightly less luminous and less massive than the Milky Way — is located about 13 billion light-years from Earth in the Virgo constellation cluster. It was discovered hidden behind the galaxy cluster Abell 1689 in 2007 and confirmed in 2015 thanks to gravitational lensing, which increased the brightness of the young galaxy by more than nine times. Since then, scientists have continued to study the galaxy as a possible analog for the evolution of other “normal” galaxies. This designation – normal – is an important distinction that has helped researchers divide the behavior and properties of A1689-zD1 into two categories: typical and unusual, with the unusual properties mimicking those of later and more massive galaxies.
“A1689-zD1 is in the very early Universe – only 700 million years after the Big Bang. This is the era when galaxies were just beginning to form,” said Hollis Akins, an astronomy student at Grinnell College and the lead author of the research. “What we are seeing in these new observations is evidence of processes that could contribute to the evolution of what we call normal galaxies, as opposed to massive galaxies. More importantly, these processes are ones that we have not previously thought applied to these normal galaxies.”
One of these unusual processes is the production and distribution of star-forming fuel throughout the galaxy, and possibly a lot of it. The team used ALMA’s highly sensitive Band 6 receiver to locate a halo of carbon gas extending well beyond the young galaxy’s center. This could be an indication of ongoing star formation in the same region, or the result of structural disturbances such as mergers or outflows in the earliest stages of the galaxy’s formation.
According to Akins, this is unusual for early galaxies. “The carbon gas that we have observed in this galaxy is typically found in the same regions as neutral hydrogen gas where new stars are also forming. If this 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 earlier galactic activity, such as mergers, that exerted complex gravitational forces on the galaxy, resulting in the ejection of much neutral gas at these great distances. In any case, the early evolution of this galaxy was likely active and dynamic, and we learn that this may be a common, albeit previously unobserved, theme in early galaxy formation.”
More than just unusual, the discovery could have significant implications for the study of galactic evolution, especially as radio observations reveal details not visible at optical wavelengths. Seiji Fujimoto, a postdoctoral fellow at the Niels Bohr Institute’s Cosmic Dawn Center and co-author of the study, said: “The emission of the carbon gas in A1689-zD1 is much more widespread than what was observed with the Hubble Space Telescope, and this could mean that early galaxies are not as small as they seem. If early galaxies are indeed larger than previously thought, it would have a major impact on the theory of galaxy formation and evolution in the early Universe.”
Led by Akins, the team also observed outflows of hot, ionized gas – often caused by intense galactic activity such as supernovae – pushing outward from the galaxy’s center. Given their potentially explosive nature, it’s possible that the outflows have something to do with the carbon halo. “Outflows occur as a result of vigorous activity, such as the explosion of supernovae – which blast nearby gaseous material out of the galaxy – or black holes at the centers of galaxies – which have strong magnetic effects that can eject material in powerful jets. Because of this, there is a strong possibility that the hot outflows have something to do with the presence of the cold carbon halo,” Akins said. “And that underscores the importance of the multiphasic, or hot to cold, nature of the effluent gas.”
Darach Watson, associate professor at the Niels Bohr Institute’s Cosmic Dawn Center and co-author of the new research, confirmed A1689-zD1 in 2015 as a high redshift galaxy, making it the most distant dust galaxy known. “We have seen these types of extended gas halo emissions from galaxies that formed later in the Universe, but seeing them in such an early galaxy means that this type of behavior is evident even in the more modest galaxies that make up most of the stars in the universe universe formed, universal is early universe. Understanding how these processes occurred in such a young galaxy is crucial to understanding how star formation occurs in the early Universe.”
Kirsten Knudsen, professor of astrophysics in the Department of Space, Earth, and Environment at Chalmers University of Technology and co-author of the research, found evidence of the A1689-zD1 dust continuum in 2017. Knudsen pointed to the fortuitous role of extreme gravitational lensing in making every new discovery in research possible. “Because A1689-zD1 is magnified more than 9x, we can see critical details that are otherwise difficult to see in ordinary observations of such distant galaxies. Ultimately, what we see here is that the galaxies of the early Universe are very complex and this galaxy will continue to offer new challenges and results for research for some time to come.”
dr Joe Pesce, NSF Program Officer for ALMA, added: “This fascinating ALMA research adds to a growing body of evidence suggesting that things are not quite as we expected in the early Universe, but they are are still really interesting and exciting!”
Spectroscopy and infrared observations of A1689-zD1 are scheduled for January 2023 using the NIRSpec Integral Field Unit (IFU) and NIRCam on the James Webb Space Telescope. The new observations will complement previous HST and ALMA data and provide a deeper and more complete multi-wavelength view of the young galaxy.
“ALMA reveals expansive cool gas and hot ionized gas in a typical star-forming galaxy at z=7.13”, Akins et al, The Astrophysical Journal.
The National Radio Astronomy Observatory (NRAO) is a National Science Foundation facility operated by Associated Universities, Inc. under a collaborative agreement.
The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organization for Astronomical Research in the Southern Hemisphere (ESO), the US National Science Foundation (NSF), and the National Institutes of Natural Sciences (NINS) Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its member states, by NSF in collaboration with the National Research Council of Canada (NRC) and the Ministry of Science and Technology (MOST), and by NINS in collaboration with Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).
The construction and operation of ALMA will be managed by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides unified leadership and administration for the construction, commissioning and operation of ALMA.
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