Elevated r-process Enrichment in Gaia Sausage and Sequoia*

Aguado, David S.; Belokurov, Vasily; Myeong, G. C.; Evans, N. W.; Kobayashi, Chiaki; Sbordone, L.; Chanamé, Julio; Navarrete, C.; Koposov, S. E.

doi:10.3847/2041-8213/abdbb8

Cited by 88 publications

(135 citation statements)

References 66 publications

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“…For Y and Ba, the abundances of the chemical selection are above those of the dynamical selection, whereas for Zr, La, Ce, Nd, and Eu this is not the case. We note that our distributions (see also Aguado et al 2021) of Y and Ba are higher than those by Nissen & Schuster (2011). Comparing our distribution with the measurements by Venn et al (2004) for Ba and La as well as Fishlock et al (2017) for Zn, Zr, La, and Nd strengthens the impression from Section 3.1 that the GALAH+ DR3 measurements for these elements are close to or below the detection limit.…”

Section: Neutron-capture Elements: Rb To Eusupporting

confidence: 81%

“…Neutron-capture elements are the least well measured elements in GALAH+ DR3, especially at low metallicities. Because of the limited amount of measurements, we will not comment on the distributions for Rb, Sr (see, however, Aguado et al 2021), and Ru. For the neutron-capture elements, we also see the largest dispersion in the distributions, that is typically on the order of 0.2-0.3 dex.…”

Section: Neutron-capture Elements: Rb To Eumentioning

confidence: 99%

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The GALAH Survey: chemical tagging and chrono-chemodynamics of accreted halo stars with GALAH+ DR3 andGaiaeDR3

Buder

Lind

Ness

et al. 2021

Monthly Notices of the Royal Astronomical Society

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Since the advent of Gaia astrometry, it is possible to identify massive accreted systems within the Galaxy through their unique dynamical signatures. One such system, Gaia-Sausage-Enceladus (GSE), appears to be an early “building block” given its virial mass >1010 M⊙ at infall (z ∼ 1 − 3). In order to separate the progenitor population from the background stars, we investigate its chemical properties with up to 30 element abundances from the GALAH+ Survey Data Release 3 (DR3). To inform our choice of elements for purely chemically selecting accreted stars, we analyse 4164 stars with low-α abundances and halo kinematics. These are most different to the Milky Way stars for abundances of Mg, Si, Na, Al, Mn, Fe, Ni, and Cu. Based on the significance of abundance differences and detection rates, we apply Gaussian mixture models to various element abundance combinations. We find the most populated and least contaminated component, which we confirm to represent GSE, contains 1049 stars selected via [Na/Fe] vs. [Mg/Mn] in GALAH+ DR3. We provide tables of our selections and report the chrono-chemodynamical properties (age, chemistry, and dynamics). Through a previously reported clean dynamical selection of GSE stars, including $30 < \sqrt{J_R / \, \mathrm{kpc\, km\, s^{-1}}} < 55$, we can characterise an unprecedented 24 abundances of this structure with GALAH+ DR3. With our chemical selection we characterise the dynamical properties of the GSE, for example mean $\sqrt{J_R / \, \mathrm{kpc\, km\, s^{-1}}} = 26^{+9}_ {-14}$. We find only $(29\pm 1)\%$ of the GSE stars within the clean dynamical selection region. Our methodology will improve future studies of accreted structures and their importance for the formation of the Milky Way.

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Section: Neutron-capture Elements: Rb To Eusupporting

confidence: 81%

Section: Neutron-capture Elements: Rb To Eumentioning

confidence: 99%

The GALAH Survey: chemical tagging and chrono-chemodynamics of accreted halo stars with GALAH+ DR3 andGaiaeDR3

Buder

Lind

Ness

et al. 2021

Monthly Notices of the Royal Astronomical Society

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“…Such simplistic approaches should be testified by the future cosmological zoom-in simulations that resolve the UFDsized structures of MW-like galaxies. More measurements of stellar abundances in terms of both the number of stars and their accuracy will serve to refine the modelling of the enrichment history of the r-process elements in the MW (e.g., R-Process Alliance, Hansen et al 2018;Sakari et al 2018;Holmbeck et al 2020;Gudin et al 2021;GALAH, Buder et al 2021;Aguado et al 2021;Matsuno et al 2021;LAMOST, Chen et al 2021). In particular, more data are highly desired for UFDs and classical dwarf spheroidals as survivors from the early Galactic merging history.…”

Section: Discussionmentioning

confidence: 99%

Neutron star mergers as the astrophysical site of the r-process in the Milky Way and its satellite galaxies

Wanajo

Hirai

Prantzos

2021

Monthly Notices of the Royal Astronomical Society

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Recent progress of nucleosynthesis work as well as the discovery of a kilonova associated with the gravitational-wave source GW170817 indicates that neutron star mergers (NSM) can be a site of the r-process. Several studies of galactic chemical evolution, however, have pointed out inconsistencies between this idea and the observed stellar abundance signatures in the Milky Way: (a) the presence of Eu at low (halo) metallicity and (b) the descending trend of Eu/Fe at high (disc) metallicity. In this study, we explore the galactic chemical evolution of the Milky Way’s halo, disc and satellite dwarf galaxies. Particular attention is payed to the forms of delay-time distributions for both type Ia supernovae (SN Ia) and NSMs. The Galactic halo is modeled as an ensemble of independently evolving building-block galaxies with different masses. The single building blocks as well as the disc and satellite dwarfs are treated as well-mixed one-zone systems. Our results indicate that the aforementioned inconsistencies can be resolved and thus NSMs can be the unique r-process site in the Milky Way, provided that the delay-time distributions satisfy the following conditions: (i) a long delay (∼1 Gyr) for the appearance of the first SN Ia (or a slow early increase of its number) and (ii) an additional early component providing $\gtrsim 50{{\ \rm per\ cent}}$ of all NSMs with a delay of ∼0.1 Gyr. In our model, r-process-enhanced and r-process-deficient stars in the halo appear to have originated from ultra-faint dwarf-sized and massive building blocks, respectively. Our results also imply that the natal kicks of binary neutron stars have a little impact on the evolution of Eu in the disc.

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“…Often this is achieved by combining the complete phase-space information with detailed chemistry from spectroscopic surveys (e.g. Aguado et al 2021;Gudin et al 2021;Limberg et al 2021a,b;Montalbán et al 2021;Naidu et al 2021;Shank et al 2021).…”

Section: Introductionmentioning

confidence: 99%

Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia EDR3 stars brighter than G = 18.5

Anders

Khalatyan

Queiroz

et al. 2022

A&A

165

142

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We present a catalogue of 362 million stellar parameters, distances, and extinctions derived from Gaia’s Early Data Release (EDR3) cross-matched with the photometric catalogues of Pan-STARRS1, SkyMapper, 2MASS, and AllWISE. The higher precision of the Gaia EDR3 data, combined with the broad wavelength coverage of the additional photometric surveys and the new stellar-density priors of the StarHorse code, allows us to substantially improve the accuracy and precision over previous photo-astrometric stellar-parameter estimates. At magnitude G = 14 (17), our typical precisions amount to 3% (15%) in distance, 0.13 mag (0.15 mag) in V-band extinction, and 140 K (180 K) in effective temperature. Our results are validated by comparisons with open clusters, as well as with asteroseismic and spectroscopic measurements, indicating systematic errors smaller than the nominal uncertainties for the vast majority of objects. We also provide distance- and extinction-corrected colour-magnitude diagrams, extinction maps, and extensive stellar density maps that reveal detailed substructures in the Milky Way and beyond. The new density maps now probe a much greater volume, extending to regions beyond the Galactic bar and to Local Group galaxies, with a larger total number density. We publish our results through an ADQL query interface (gaia.aip.de) as well as via tables containing approximations of the full posterior distributions. Our multi-wavelength approach and the deep magnitude limit render our results useful also beyond the next Gaia release, DR3.

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Elevated r-process Enrichment in Gaia Sausage and Sequoia*

Cited by 88 publications

References 66 publications

The GALAH Survey: chemical tagging and chrono-chemodynamics of accreted halo stars with GALAH+ DR3 andGaiaeDR3

The GALAH Survey: chemical tagging and chrono-chemodynamics of accreted halo stars with GALAH+ DR3 andGaiaeDR3

Neutron star mergers as the astrophysical site of the r-process in the Milky Way and its satellite galaxies

Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia EDR3 stars brighter than G = 18.5

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