Birds of a Feather? Magellan/IMACS Spectroscopy of the Ultra-faint Satellites Grus II, Tucana IV, and Tucana V*

Simon, Joshua D.; Li, Ting S.; Erkal, Denis; Pace, Andrew B.; Drlica-Wagner, A.; James, D. J.; Marshall, J. L.; Bechtol, K.; Hansen, Terese T.; Kuêhn, K.; Lidman, C.; Allam, S.; Annis, J.; Ávila, S.; Bertin, E.; Brooks, D.; Burke, D. L.; Rosell, A. Carnero; Kind, M. Carrasco; Carretero, J.; Costa, L. N. da; Vicente, J. De; Desai, S.; Doel, P.; Eifler, T. F.; Everett, S.; Fosalba, P.; Frieman, Joshua A.; García-Bellido, J.; Gaztañaga, E.; Gerdes, D. W.; Gruen, David; Gruendl, R. A.; Gschwend, J.; Gutiérrez, G.; Hollowood, D. L.; Honscheid, K.; Krause, E.; Kuropatkin, N.; MacCrann, N.; Maia, M. A. G.; March, M.; Miquel, R.; Palmese, A.; Paz-Chinchón, F.; Plazas, A. A.; Reil, K.; Roodman, A.; Sánchez, E.; Santiago, B.; Scarpine, V.; Schubnell, M.; Serrano, S.; Smith, M.; Suchyta, E.; Tarlè, G.; Walker, A. R.

doi:10.3847/1538-4357/ab7ccb

Cited by 61 publications

(63 citation statements)

References 117 publications

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“…The mean value of the resulting velocities along with the standard deviation are listed in Table 1. Our values are different from the velocities determined for the stars by Simon et al (2020), who find V hel =−108.6±1.0 kms −1 , −108.1±1.0kms −1 , and −109.3±1.0kms −1 for J220423, J220409, and J220352, respectively. However, J220423 and J220409 were both observed at high airmass, 1.8 and 1.6 respectively, which can cause offsets in the radial velocities (Ji et al 2020), and J220352 is likely in a binary system (Simon et al 2020).…”

Section: Observationscontrasting

confidence: 99%

“…It is not yet clear if a different birth environment like the LMC could result in the different chemical abundance patterns seen in some of the LMC-associated UFD galaxies (Nagasawa et al 2018). However, as a counter-argument, Simon et al (2020) find it unlikely that GruII is associated with the LMC.…”

Section: Other Alternativesmentioning

confidence: 99%

“…The first spectrum of DES J220352.01-462446.5 (J220352) was observed in 2017 August and the second in 2018 November along with spectra of DESJ220318.62-464116.4 (J220318) and DESJ220253.88-463522.6 (J220253). Three of the stars (J220423, J220409, and J220352) were selected as spectroscopically confirmed members from medium-resolution velocity and metallicity measurements (Simon et al 2020). The brightest star, J220423, was first identified as a member from an observing run with the Anglo-Australia Telescope (AAT) in 2016 July.…”

Section: Observationsmentioning

confidence: 99%

“…While the AAT observing run was mostly for targeting the Tucana III stream (see details in Li et al 2018), a small fraction of time was also spent on bright candidate members in GruII and Tucana IV during nights with cirrus cloud coverage, to identify bright member stars for MIKE observations. The membership of J220423 was subsequently confirmed with Magellan/IMACS spectroscopy (Simon et al 2020). The remaining two stars, J220318 and J220253, were selected as member candidates from Pace & Li (2019), although with relatively low membership probabilities (p i =0.47 and p i =0.14, respectively).…”

Section: Observationsmentioning

confidence: 99%

“…GruII was identified as a candidate MW satellite galaxy in the Dark Energy Survey (DES) at a distance of 53kpc (Drlica-Wagner et al 2015). Spectroscopic follow-up of the system was presented by Simon et al (2020), who were unable to resolve a velocity dispersion or detect a metallicity spread, indicative of dwarf galaxies, for the system. However, based on the large physical size (r 1/2 =94 pc) and low metallicity ([ ] = - Fe H 2.51 0.11), Simon et al (2020) classify the system as a likely dwarf galaxy.…”

Section: Introductionmentioning

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: Observationscontrasting

confidence: 99%

Section: Other Alternativesmentioning

confidence: 99%

Section: Observationsmentioning

confidence: 99%

Section: Observationsmentioning

confidence: 99%

Section: Introductionmentioning

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

Frebel,

2023

Handbook of Nuclear Physics

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Birds of a Feather? Magellan/IMACS Spectroscopy of the Ultra-faint Satellites Grus II, Tucana IV, and Tucana V*

Abstract: We present Magellan/IMACS spectroscopy of three recently discovered ultra-faint Milky Way satellites, GrusII, TucanaIV, and TucanaV. We measure systemic velocities of = - v 110.0 0.5 hel -

Cited by 61 publications

References 117 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*

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

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

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