Chemical Abundance Analysis of Tucana III, the Second r-process Enhanced Ultra-faint Dwarf Galaxy*

Marshall, J. L.; Hansen, Terese T.; Simon, Joshua D.; Li, T. S.; Bernstein, R. A.; Kuêhn, K.; Pace, Andrew B.; DePoy, D. L.; Palmese, A.; Pieres, A.; Strigari, Louis E.; Drlica-Wagner, A.; Bechtol, K.; Lidman, C.; Nagasawa, D. Q.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Burke, D. L.; Rosell, A. Carnero; Kind, M. Carrasco; Carretero, J.; Cunha, C. E.; D’Andrea, C. B.; Costa, L. N. da; Vicente, J. De; Desai, S.; Doel, P.; Eifler, T. F.; Flaugher, B.; Fosalba, P.; Frieman, J.; García-Bellido, J.; Gaztañaga, E.; Gerdes, D. W.; Gruendl, R. A.; Gschwend, J.; Gutiérrez, G.; Hartley, W. G.; Hollowood, D. L.; Honscheid, K.; Hoyle, B.; James, D. J.; Kuropatkin, N.; Maia, M. A. G.; Menanteau, F.; Miller, Christopher J.; Miquel, R.; Plazas, A. A.; Sanchez, E. J.; Santiago, B.; Scarpine, V.; Schubnell, M.; Serrano, S.; Sevilla-Noarbe, I.; Smith, M.; Soares-Santos, M.; Suchyta, E.; Swanson, M. E. C.; Tarlè, G.; Wester, W.

doi:10.3847/1538-4357/ab3653

Cited by 55 publications

(32 citation statements)

References 75 publications

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“…Another possible explanation for the chemically peculiar stars in GruII is that the chemical enrichment and star formation in systems like GruII are stochastic and inhomogeneous. It can be seen in Figure 4 that other UFD galaxy stars exhibit a similar α-element signature as the three GruII and two Her stars, including the r-process enhanced galaxies RetII and TucIII (Ji et al 2016c;Marshall et al 2019). In these systems, however, the high [ ] Mg Ca stars are outliers and the majority of the stars exhibit enhancements in the α elements similar to metal-poor halo stars.…”

Section: Stochastic Chemical Enrichmentmentioning

confidence: 85%

“…Recent exploration of the chemical abundances in ultrafaint dwarf (UFD) galaxies have revealed abundance patterns of these objects similar to those that have been detected in the majority of metal-poor Milky Way (MW) halo stars (Frebel & Norris 2015). However, some notable outliers have also been observed, for example ReticulumII (Ret II) and TucanaIII (Tuc III) both show enhancement in rapid neutron-capture (r-process) elements (Ji et al 2016a;Roederer et al 2016;Hansen et al 2017;Marshall et al 2019). This chemical signature is also seen in a very small fraction of MW halo stars (Barklem et al 2005;Hansen et al 2018).…”

Section: Introductionmentioning

confidence: 81%

“…Stellar parameter determination and abundance analysis was done following the techniques described in Hansen et al (2017) and Marshall et al (2019), using the 2017 version of MOOG (Sneden 1973) and making the assumption of local thermodynamic equilibrium (LTE) and including Rayleigh scattering treatment as described by Sobeck et al (2011). 52 The stellar parameters for the three stars were determined spectroscopically from equivalent width (EW) measurements of Fe I and Fe II lines.…”

Section: Stellar Parameter Determination and Abundance Analysismentioning

confidence: 99%

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Chemical Analysis of the Ultrafaint Dwarf Galaxy Grus II. Signature of High-mass Stellar Nucleosynthesis*

Hansen¹,

Marshall²,

Simon³

et al. 2020

ApJ

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We present a detailed abundance analysis of the three brightest member stars at the top of the giant branch of the ultrafaint dwarf (UFD) galaxy GrusII. All stars exhibit a higher than expected [Mg/Ca] ratio compared to metalpoor stars in other UFD galaxies and in the Milky Way (MW) halo. Nucleosynthesis in high-mass ( 20 M e) corecollapse supernovae has been shown to create this signature. The abundances of this small sample (three) stars suggests the chemical enrichment of GrusII could have occurred through substantial high-mass stellar evolution, and is consistent with the framework of a top-heavy initial mass function. However, with only three stars it cannot be ruled out that the abundance pattern is the result of a stochastic chemical enrichment at early times in the galaxy. The most metal-rich of the three stars also possesses a small enhancement in rapid neutron-capture (r-process) elements. The abundance pattern of the r-process elements in this star matches the scaled r-process pattern of the solar system and r-process enhanced stars in other dwarf galaxies and in the MW halo, hinting at a common origin for these elements across a range of environments. All current proposed astrophysical sites of r-process element production are associated with high-mass stars, thus the possible top-heavy initial mass function of GrusII would increase the likelihood of any of these events occurring. The time delay between the α and r-process element enrichment of the galaxy favors a neutron star merger as the origin of the r-process elements in GrusII. Unified Astronomy Thesaurus concepts: Chemical abundances (224); Dwarf galaxies (416); Chemically peculiar stars (226); Stellar abundances (1577)

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Section: Stochastic Chemical Enrichmentmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 81%

Section: Stellar Parameter Determination and Abundance Analysismentioning

confidence: 99%

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Chemical Analysis of the Ultrafaint Dwarf Galaxy Grus II. Signature of High-mass Stellar Nucleosynthesis*

Hansen¹,

Marshall²,

Simon³

et al. 2020

ApJ

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“…In Fig. 3, we highlight the comparison of abundances obtained with AlterBBN at high η to metal-poor stars observed in the dwarf galaxy Reticulum II [42] (purple areas) and in Tucana III [48] (orange areas). In these galaxies, which are highly dark-matter-dominated, there are hints of an enrichment in r-process elements, which in the absence of the most established astrophysical explanation, namely neutron star binaries [51], could possibly correspond to a primordial component.…”

Section: Comparison With Metal-poor Stars In Dwarf Spheroidal and mentioning

confidence: 99%

“…4. Comparison of AlterBBN europium abundance (black line, summed over the isotopes) as a function of η with metalpoor halo star data [46] (blue dashed areas), dwarf spheroidal faint galaxy data [47] (green dashed areas), and two sets of rprocess enhanced dwarf galaxy data: Reticulum II [42] (purple areas) and Tucana III [48] (orange areas). We also represent the 1σ spread of the data.…”

Section: Comparison With Metal-poor Stars In Dwarf Spheroidal and mentioning

confidence: 99%

Stellar signatures of inhomogeneous big bang nucleosynthesis

2020

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We evaluate abundance anomalies generated in patches of the Universe where the baryon-to-photon ratio was locally enhanced by possibly many orders of magnitude in the range η ¼ 10 −10-10 −1. Our study is motivated by the possible survival of rare dense regions in the early Universe, the most extreme of which, above a critical threshold, collapsed to form primordial black holes. If this occurred, one may expect there to also be a significant population of early-forming stars that formed in similar but subthreshold patches. We derive a range of element abundance signatures by performing BBN simulations at high values of the baryon-to-photon ratio that may be detectable in any surviving first-generation stars of around a solar mass. Our predictions apply to metal-poor Galactic halo stars, to old globular star clusters, and to dwarf galaxies, and we compare with observations in each of these cases.

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Observations of R-Process Stars in the Milky Way and Dwarf Galaxies

Frebel

2022

Handbook of Nuclear Physics

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This chapter presents an overview of the recent progress on spectroscopic observations of metal-poor stars with r-process element signatures found in the Milky Way's stellar halo and satellite dwarf galaxies. Major empirical lessons related to the origins of the r-process are discussed, including the universality of the observed r-process pattern and deviations from universality among the light r-process elements and actinides. Different astrophysical sites of the r-process based on theoretical expectations are presented, including common and rare supernovae and neutron star mergers. A major distinguishing factor between r-process sites is their delay time distribution. The best constraints on the detailed r-process pattern come from Galactic halo r-process stars, but these cannot provide information on the environment of the stars' birth gas clouds. Studying r-process enrichment within dwarf galaxies can remedy the situation despite the fact that high-resolution spectroscopic observations of individual stars in these systems are very difficult to obtain. A general overview of dwarf galaxy properties and chemical evolution expectations depending on their mass and star formation duration is provided. The r-process trends depend on the stellar mass and star formation durations of dwarf galaxies in a way that clearly shows that the r-process is rare, prolific, and has both prompt and delayed sources. This work complements ongoing theoretical heavy-element nucleosynthesis explorations and experimental measurements of the properties of r-process nuclei, such as with the Facility for Rare Isotope Beams.

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Chemical Abundance Analysis of Tucana III, the Second r-process Enhanced Ultra-faint Dwarf Galaxy*

Cited by 55 publications

References 75 publications

Chemical Analysis of the Ultrafaint Dwarf Galaxy Grus II. Signature of High-mass Stellar Nucleosynthesis*

Chemical Analysis of the Ultrafaint Dwarf Galaxy Grus II. Signature of High-mass Stellar Nucleosynthesis*

Stellar signatures of inhomogeneous big bang nucleosynthesis

Observations of R-Process Stars in the Milky Way and Dwarf Galaxies

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