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Timing the r-proces...
Timing the r-process Enrichment of the Ultra-faint Dwarf Galaxy Reticulum II
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Simon, Joshua D. (författare)
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- Hansen, Terese T (författare)
- Stockholms universitet,Institutionen för astronomi
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Wilkinson, R. D. (författare)
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(creator_code:org_t)
- 2023-02-10
- 2023
- Engelska.
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 944:1
- Relaterad länk:
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https://doi.org/10.3...
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visa fler...
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https://urn.kb.se/re...
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https://doi.org/10.3...
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Abstract
Ämnesord
Stäng
- The ultra-faint dwarf galaxy Reticulum II (Ret II) exhibits a unique chemical evolution history, with % of its stars strongly enhanced in r-process elements. We present deep Hubble Space Telescope photometry of Ret II and analyze its star formation history. As in other ultra-faint dwarfs, the color–magnitude diagram is best fit by a model consisting of two bursts of star formation. If we assume that the bursts were instantaneous, then the older burst occurred around the epoch of reionization, forming ∼80% of the stars in the galaxy, while the remainder of the stars formed ∼3 Gyr later. When the bursts are allowed to have nonzero durations, we obtain slightly better fits. The best-fitting model in this case consists of two bursts beginning before reionization, with approximately half the stars formed in a short (100 Myr) burst and the other half in a more extended period lasting 2.6 Gyr. Considering the full set of viable star formation history models, we find that 28% of the stars formed within 500 ± 200 Myr of the onset of star formation. The combination of the star formation history and the prevalence of r-process-enhanced stars demonstrates that the r-process elements in Ret II must have been synthesized early in its initial star-forming phase. We therefore constrain the delay time between the formation of the first stars in Ret II and the r-process nucleosynthesis to be less than 500 Myr. This measurement rules out an r-process source with a delay time of several Gyr or more, such as GW170817.
Ämnesord
- NATURVETENSKAP -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)
Nyckelord
- Dwarf galaxies
- Local Group
- Stellar populations
- Galaxy ages
- HST photometry
- Nucleosynthesis
- R-process
Publikations- och innehållstyp
- ref (ämneskategori)
- art (ämneskategori)
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