Researchers measure size-luminosity relationship of galaxies less than a billion years after the Big Bang

Researchers measure size-luminosity relationship of galaxies less than a billion years after the Big Bang

by the Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo

Figure 1. Two exceptionally bright galaxies captured in the GLASS-JWST program. These galaxies existed about 450 and 350 million years after the Big Bang (at a redshift of about 10.5 and 12.5, respectively), and the sizes are about 500 parsecs and 170 parsecs, respectively. Credit: NASA, ESA, CSA, Tommaso Treu (UCLA)

An international team of researchers, including the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) has studied the relationship between galaxy size and luminosity of some of the oldest galaxies in the universe taken by the new James Webb Space Telescope (JWST), less than a billion years after the Big Bang, reports a new study in Letters from the Astrophysical Journal.


The result is part of the Grim Lens-Amplified Survey from Space (GLASS), Early-Release Science Program, led by University of California, Los Angeles, Professor Tommaso Treu. It aims to study the early universe when the first stars/galaxies ignited, which ionized the neutral gas in the universe at that time and allowed the light to shine. This is called the age of reionization.

However, the details of reionization have remained unknown because telescopes until today have not been able to observe galaxies during this period of the universe’s history in detail. Learning more about the age of reionization would help researchers understand how stars and galaxies evolved to create the universe as we see it today.

A study, led by IPMU JSPS Kavli Fellow Lilan Yang and including project researcher Xuheng Ding, used multiband NIRCAM imaging data from the GLASS-JWST program to measure the size and luminosity of the galaxy to learn the morphology and size-luminosity relationship from rest- UV optical frame.

“This is the first time we can study the rest-frame optical properties of the galaxy at redshift greater than 7 with JWST, and size-luminosity is important for determining the shape of the luminosity function, which indicates the primary sources responsible for cosmic reionization. that is, numerous faint galaxies or relatively less luminous galaxies.

“The original wavelength of light will change to a longer wavelength as it travels from the early universe to us. Thus, the rest frame wavelength is used to clarify their intrinsic wavelength rather than the observed wavelength. Previously, with the Hubble Space Telescope, we only know the properties of galaxies in the rest-frame UV band. Now with JWST, we can measure wavelengths longer than UV,” said first author Yang.

Researchers measure size-luminosity relationship of galaxies less than a billion years after the Big Bang

Figure 2: Size–luminosity relations of galaxies observed in five wavelength bands with fixed slope due to limited data. The black solid and dashed lines in panel F150W show the relation derived from HST data by Shibuya et al. (2015; z ~ 8) and Huang et al. (2013; z ∼ 5) at a similar rest-frame wavelength, respectively. Credit: Yang et al.

The researchers discovered the first optical size-luminosity relation for galaxies at redshift greater than 7, or about 800 million years after the Big Bang, allowing them to study size as a function of wavelength. They found that the average size at the reference luminosity is about 450–600 parsecs and decreased slightly from the optical rest frame to the UV. But was this expected?

“The answer is that we don’t know what to expect. Previous simulation studies provide a number of predictions,” Yang said.

The team also found that the slope of the size-luminosity relation was somewhat steeper in the shortest wavelength band when allowing the slope to vary.

“This would suggest a higher surface luminosity density at shorter wavelength, so less observational incompleteness correction when estimating the luminosity function, but the result is inconclusive. We don’t want to over-interpret here,” Yang said.

The team’s work was published on October 18, 2022, in Letters from the Astrophysical Journal.

More information:
L. Yang et al., Early results from GLASS-JWST. V: First relation between optical size and rest-frame luminosity of galaxies at z > 7, Letters from the Astrophysical Journal (2022). DOI: 10.3847/2041-8213/ac8803

Provided by the Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo

Citation: Researchers measure size-luminosity relation of galaxies less than a billion years after the Big Bang (2023 January 13) Retrieved January 14, 2023 from https://phys.org/news/2023-01-size-luminosity -galaxies-billion- years-mare.html

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