Science

Voyage to the Ends of Time: The James Webb Space Telescope Reveals the Most Distant Galaxies

The JWST Advanced Deep Extragalactic Survey (JADES) focused on the area within and around the ultra-deep field of the Hubble Space Telescope. Using Webb’s NIRCam instrument, the scientists observed the field in nine different infrared wavelength ranges. From these images (shown on the left), the team searched for faint galaxies visible in the infrared but whose spectra abruptly cut off at a critical wavelength known as the Lyman Break. Webb’s NIRSpec instrument then provided an accurate measurement of each galaxy’s redshift (shown right). Four of the galaxies studied are particularly special, as they were found to be at an unprecedented time. These galaxies date back less than 400 million years after the big bang, when the universe was only 2% of its current age. In the background image, blue represents light at 1.15 microns (115 W), green at 2.0 microns (200 W), and red at 4.44 microns (444 W). In the cutout images, blue is a combination of 0.9 and 1.15 microns (090W+115W), green is 1.5 and 2.0 microns (150W+200W), and red is 2.0 , 2.77 and 4.44 microns (200W+277W+444W). Credit: NASA, ESA, CSA, STScI, M. Zamani (ESA/Webb) and L. Hustak (STScI). Sciences: B. Robertson (UCSC), S. Tacchella (Cambridge), E. Curtis-Lake (Hertfordshire), S. Carniani (Scuola Normale Superiore) and the JADES collaboration

Astronomers report the most distant known galaxies detected and confirmed by JWST.

An international team of astronomers has discovered the oldest and most distant galaxies confirmed to date using data from the James Webb Space Telescope (JWST). The telescope captured the light emitted by these galaxies over 13.4 billion years ago, which means the galaxies date back less than 400 million years after the Big Bang, while the universe does not was only 2% of his current age.

JWST’s initial observations yielded several candidate galaxies at extreme distances, as had earlier observations with the Hubble Space Telescope. Now, four of these targets have been confirmed by obtaining long spectroscopic observations, which not only provide reliable measurements of their distances, but also allow astronomers to characterize the physical properties of galaxies.

“We discovered galaxies at incredibly early times in the distant universe,” said Brant Robertson, professor of astronomy and astrophysics at UC Santa Cruz. “With JWST, for the first time, we can now find galaxies that far away and then confirm by spectroscopy that they really are that far away.”

Astronomers measure the distance to a galaxy by determining its redshift. Due to the expansion of the universe, distant objects appear to recede from us and their light is stretched to longer, redder wavelengths by the Doppler effect. Photometric techniques based on images captured through various filters can provide redshift estimates, but definitive measurements require spectroscopy, which separates light from an object into its component wavelengths.

What is Redshift Cosmological Culture?

(Click the image to see the full infographic.) The universe is expanding, and this expansion stretches light traveling through space in a phenomenon known as cosmological redshift. The greater the redshift, the greater the distance the light travels. As a result, telescopes with infrared detectors are needed to see the light from the earliest, most distant galaxies. Credit: NASA, ESA, AND L. Hustak (STSci)

The new findings focus on four galaxies with redshifts greater than 10. Two galaxies originally observed by Hubble have now confirmed redshifts of 10.38 and 11.58. The two most distant galaxies, both detected in JWST images, have redshifts of 13.20 and 12.63, making them the most distant galaxies confirmed by spectroscopy to date. A redshift of 13.2 corresponds to about 13.5 billion years.

“These go way beyond what we could have imagined finding before JWST,” Robertson said. “At redshift 13, the universe is only about 325 million years old.”

Robertson and Emma Curtis-Lake of the University of Hertfordshire (UK) are lead authors on two papers on the findings which have not yet gone through the peer review process (see links below ).

The observations are the result of a collaboration of scientists who led the development of two of Webb’s onboard instruments, the near-infrared camera (NIRCam) and the near-infrared spectrograph (NIRSpec). The study of the weakest and oldest galaxies was the main motivation for the concepts of these instruments. In 2015, the instrument teams came together to propose the JWST Advanced Deep Extragalactic Survey (JADES), an ambitious program that has been allocated just over a month of telescope time and is designed to provide a view of the primordial universe unprecedented in depth and detail. JADES is an international collaboration of over eighty astronomers from ten countries.

“These results are the culmination of why the NIRCam and NIRSpec teams have come together to run this observing program,” said Marcia Rieke, NIRCam principal investigator at the University of Arizona.

The JADES program began with NIRCam, using over 10 days of mission time to observe a small patch of sky in and around the Hubble Ultra Deep Field. Astronomers have studied this region for more than 20 years with almost all major telescopes. The JADES team observed the field in nine different infrared wavelength ranges, capturing exquisite images that reveal nearly 100,000 distant galaxies, each billions of light-years away.

The team then used the NIRSpec spectrograph for a single three-day observation period to collect light from 250 faint galaxies. This gave precise measurements of the redshift and revealed the properties of gas and stars in these galaxies.

“With these measurements, we can know the intrinsic luminosity of galaxies and determine how many stars they have,” Robertson said. “Now we can start to really distinguish how galaxies are assembled over time.”

Co-author Sandro Tacchella from the University of Cambridge in the UK added: “It is difficult to understand galaxies without understanding the initial periods of their development. Just like with humans, much of what happens later depends on the impact of these early generations of stars. So many questions about galaxies have been waiting for Webb’s transformative opportunity, and we’re thrilled to be able to play a part in telling this story.

According to Robertson, the formation of stars in these first galaxies would have started about 100 million years earlier than the age at which they were observed, pushing back the formation of the first stars to about 225 million years after the

big Bang
The Big Bang is the main cosmological model explaining how the universe as we know it began about 13.8 billion years ago.

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“We are seeing evidence of star formation about as early as we could expect based on our models of galaxy formation,” he said.

Other teams have identified candidate galaxies at even higher redshifts based on photometric analyses of JWST images, but these have yet to be confirmed by spectroscopy. JADES will continue in 2023 with a detailed study of another field, this one centered on the iconic Hubble Deep Field, and then a return to the Ultra Deep Field for another round of deep imaging and spectroscopy. Many more candidates in the field await spectroscopic investigation, with hundreds of hours of additional time already approved.

For more on this research, see NASA’s Webb Space Telescope Discovers Earliest Galaxies in the Universe.

References:

“Discovery and properties of the earliest galaxies with confirmed distances” by B. E. Robertson, S. Tacchella, B. D. Johnson, K. Hainline, L. Whitler, D. J. Eisenstein, R. Endsley, M. Rieke, D. P. Stark, S. Alberts, A. Dressler, E. Egami, R. Hausen, G. Rieke, I. Shivaei, C. C. Williams, C. N. A. Willmer, S. Arribas g, N. Bonaventura, A. Bunker, A. J. Cameron, S. Carniani, S. Charlot, J. Chevallard, M. Curti, E. Curtis-Lake, F. D’Eugenio, P. Jakobsen, T. J. Looser, N. Lützgendorf, R. Maiolino, M. V. Maseda, T. Rawle, H.-W. Rix, R. Smit, H. Übler, C. Willott, J. Witstok, S. Baum, R. Bhatawdekar, K. Boyett, Z. Chen, A. de Graaff, M. Florian, J. M. Helton, R. E. Hviding, Z. Ji, N. Kumari, J. Lyu, E. Nelson, L. Sandles, A. Saxena, K. A. Suess, F. Sun, M. Topping and I. E. B. Wallace, 17 November 2022, Astrophysics > Astrophysics of Galaxies.
arXiv:2212.04480

“Spectroscopic confirmation of four metal-poor galaxies at z=10.3-13.2” by Emma Curtis-Lake, Stefano Carniani, Alex Cameron, Stephane Charlot, Peter Jakobsen, Roberto Maiolino, Andrew Bunker, Joris Witstok, Renske Smit, Jacopo Chevallard, Chris Willott, Pierre Ferruit, Santiago Arribas, Nina Bonaventura, Mirko Curti, Francesco D’Eugenio, Marijn Franx, Giovanna Giardino, Tobias J. Looser, Nora Lützgendorf, Michael V. Maseda, Tim Rawle, Hans-Walter Rix, Bruno Rodriguez del Pino, Hannah Übler, Marco Sirianni, Alan Dressler, Eiichi Egami, Daniel J. Eisenstein, Ryan Endsley, Kevin Hainline, Ryan Hausen, Benjamin D. Johnson, Marcia Rieke, Brant Robertson, Irene Shivaei, Daniel P. Stark, Sandro Tacchella, Christina C. Williams, Christopher N. A. Willmer, Rachana Bhatawdekar, Rebecca Bowler, Kristan Boyett, Zuyi Chen, Anna de Graaff, Jakob M. Helton, Raphael E. Hviding, Gareth C. Jones, Nimisha Kumari, Jianwei Lyu, Erica Nelson, Michele Perna, Lester Sandles, Aayush Saxena, Katherine A. Suess, Fengwu Sun, Michael W. Topping, Imaan E. B. Wallace and Lily Whitler, 8 December 2022, Astrophysics > Astrophysics of Galaxies.
arXiv:2212.04568


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