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by Tomasz Nowakowski
, Phys.org
Three-color near-infrared composite picture of I Zwicky 18 in NIRCam F115W (blue), F200W (inexperienced), and F356W (pink). Credit score: Hirschauer et al, 2024
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Three-color near-infrared composite picture of I Zwicky 18 in NIRCam F115W (blue), F200W (inexperienced), and F356W (pink). Credit score: Hirschauer et al, 2024
Utilizing the James Webb Area Telescope, astronomers have performed near- and mid-infrared observations of a particularly metal-poor blue compact dwarf galaxy generally known as I Zwicky 18. Outcomes of the observational marketing campaign, introduced in a paper printed March 11 on the arXiv preprint server, ship necessary data concerning stellar populations on this galaxy.
Blue compact dwarfs (BCDs) are low-luminosity and low-metal content material dwarf galaxies experiencing violent bursts of star formation. They’re characterised by a compact optical look and H II-region-like spectra on account of extremely concentrated starburst actions.
I Zwicky 18 is the archetypal BCD positioned about 59 million mild years away within the constellation Ursa Main. This BCD is likely one of the most extraordinarily metal-poor galaxies generally known as it’s virtually completely composed of hydrogen and helium.
Earlier observations have discovered that I Zwicky 18 is presently experiencing a interval of intensely elevated star-formation fee (SFR) and could also be nonetheless creating Inhabitants III stars—hypothetical extraordinarily huge stars, poor in components heavier than helium, believed to have been shaped within the early universe. Therefore, this galaxy is perceived as a perfect laboratory to check each the younger and advanced star demographics in an surroundings analogous to that discovered shortly after the Massive Bang.
That’s the reason a group of astronomers led by Alec S. Hirschauer of the Area Telescope Science Institute (STScI) in Baltimore, Maryland, determined to take a more in-depth have a look at I Zwicky 18. They employed JWST’s Close to Infrared Digital camera (NIRCam) and Mid-Infrared Instrument (MIRI) to analyze the stellar content material of this galaxy.
The observations performed by Hirschauer’s group recognized excessive populations of vibrant, lately shaped huge stars in I Zwicky 18, positioned predominantly among the many galaxy’s two central lobes of star formation—the northwest (NW) and southeast (SE) elements. The obtained pictures additionally present massive supershells of mud and ionized gasoline carved out by earlier star formation and supernovae exercise.
The collected knowledge allowed the astronomers to detect candidate populations of dusty advanced stars (pink supergiants and asymptotic large department stars) in I Zwicky 18, alongside vibrant younger stellar objects (YSOs). The researchers estimated the tip of the pink large department (TRGB) and divided these sources that lie above it into left- and right-branch populations, associated to youthful (higher predominant sequence, UMS stars) and older (advanced) stars, respectively.
In accordance with the authors of the paper, their findings recommend that the prevailing demographics of I Zw 18’s NW and SE star-formation areas mirror that of youthful and older stellar populations. The research additionally proves how necessary is JWST in investigating dusty and advanced stars in compact dwarf galaxies within the early universe.
Extra data:
Alec S. Hirschauer et al, Imaging of I Zw 18 by JWST: I. Technique and First Outcomes of Dusty Stellar Populations, arXiv (2024). DOI: 10.48550/arxiv.2403.06980
Journal data:
arXiv
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