From dawn till disk: Milky Way's turbulent youth revealed by the APOGEE+Gaia data

Belokurov, Vasily; Kravtsov, Andrey

doi:10.48550/arxiv.2203.04980

Cited by 8 publications

(36 citation statements)

References 185 publications

(279 reference statements)

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“…The left panel displays two clear regimes: at [Fe/H] −1 the kinematic behavior is constant, while at [Fe/H] −1 the population becomes increasingly well-ordered (and kinematically colder) toward higher metallicities. This change in behavior of the kinematics at [Fe/H] ≈ −1 is in good agreement with Belokurov & Kravtsov (2022). The trend at [Fe/H] −1 is broadly in agreement with previous work (e.g., Lee et al 2011;Re Fiorentin et al 2019;Han et al 2020).…”

Section: Resultssupporting

confidence: 92%

“…Of the 35 NIHAO galaxies presented in Buck (2020), only one shows a transition at the low metallicity seen in the data (g5.31e11). This result is in agreement with Belokurov & Kravtsov (2022), who find that the transition between hot and cold kinematics occurs too late in the Latte (Wetzel et al 2022) and Auriga (Grand et al 2018b) simulations. For the NIHAO simulations, mergers appear to be the main driver of the enhanced star formation efficiency and non-monotonic abundance behavior.…”

Section: Comparison To Simulationssupporting

confidence: 92%

“…Despite decades of effort, this task remains challenging (see e.g., Buder et al 2022). Following the work of Hawkins et al (2015), Belokurov & Kravtsov (2022) use [Al/Fe] to separate in-situ and accreted populations. While this selection provides good separation at [Fe/H] −1.2, at lower metallicities the in-situ population overlaps in chemical space with the accreted stars, in both the diagnostic [Al/Fe] and [Mg/Mn] abundance ratios, as we show in Appendix B (and also discussed in Horta et al 2021;Belokurov & Kravtsov 2022).…”

Section: Comparison To Simulationsmentioning

confidence: 99%

“…Following the work of Hawkins et al (2015), Belokurov & Kravtsov (2022) use [Al/Fe] to separate in-situ and accreted populations. While this selection provides good separation at [Fe/H] −1.2, at lower metallicities the in-situ population overlaps in chemical space with the accreted stars, in both the diagnostic [Al/Fe] and [Mg/Mn] abundance ratios, as we show in Appendix B (and also discussed in Horta et al 2021;Belokurov & Kravtsov 2022). This means that it will be challenging to identify in-situ stars at low metallicity purely on the basis of these proposed diagnostic abundance ratios.…”

Section: Comparison To Simulationsmentioning

confidence: 99%

“…Recently, several authors have identified very metal-poor stars ([Fe/H] < −2.5) with low eccentricities reminiscent of the thin disk (Sestito et al 2020;Carter et al 2021). Using [Al/Fe] from APOGEE (Majewski et al 2017) to separate in-situ from accreted stars, Belokurov & Kravtsov (2022) identified in-situ stars to [Fe/H] ≈ −1.5. The average tangential velocity of the in-situ stars in their sample increased rapidly at [Fe/H] ≈ −1.…”

Section: Introductionmentioning

confidence: 99%

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Birth of the Galactic Disk Revealed by the H3 Survey

Conroy¹,

Weinberg²,

Naidu³

et al. 2022

Preprint

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We use chemistry ([α/Fe] and [Fe/H]), main sequence turnoff ages, and kinematics determined from H3 Survey spectroscopy and Gaia astrometry to identify the birth of the Galactic disk. We separate in-situ and accreted stars on the basis of angular momenta and eccentricities. The sequence of high−α in-situ stars persists down to at least [Fe/H] ≈ −2.5 and shows unexpected non-monotonic behavior: with increasing metallicity the population first declines in [α/Fe], then increases over the range −1.3 [Fe/H] −0.7, and then declines again at higher metallicities. The number of stars in the in-situ population rapidly increases above [Fe/H] ≈ −1. The average kinematics of these stars are hot and independent of metallicity at [Fe/H] −1 and then become increasingly cold and disk-like at higher metallicities. The ages of the in-situ, high−α stars are uniformly very old (≈ 13 Gyr) at [Fe/H] −1.3, and span a wider range (8 − 12 Gyr) at higher metallicities. Interpreting the chemistry with a simple chemical evolution model suggests that the non-monotonic behavior is due to a significant increase in star formation efficiency, which began ≈ 13 Gyr ago. These results support a picture in which the first ≈ 1 Gyr of the Galaxy was characterized by a "simmering phase" in which the star formation efficiency was low and the kinematics had substantial disorder with some net rotation. The disk then underwent a dramatic transformation to a "boiling phase", in which the star formation efficiency increased substantially, the kinematics became disk-like, and the number of stars formed increased tenfold. We interpret this transformation as the birth of the Galactic disk at z ≈ 4. The physical origin of this transformation is unclear and does not seem to be reproduced in current galaxy formation models.

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Section: Resultssupporting

confidence: 92%

Section: Comparison To Simulationssupporting

confidence: 92%

Section: Comparison To Simulationsmentioning

confidence: 99%

Section: Comparison To Simulationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Birth of the Galactic Disk Revealed by the H3 Survey

Conroy¹,

Weinberg²,

Naidu³

et al. 2022

Preprint

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Chemical and stellar properties of early-type dwarf galaxies around the Milky Way

Belokurov

Evans

2022

Nat Astron

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Early-type dwarfs (ETDs) are the end points of the evolution of lowmass galaxies whose gas supply has been extinguished. The cessation of star-formation lays bare the ancient stellar populations. A wealth of information is stored in the colours, magnitudes, metallicities and abundances of resolved stars of the dwarf spheroidal and ultra-faint galaxies around the Milky Way, allowing their chemistry and stellar populations to be studied in great detail. Here, we summarize our current understanding, which has advanced rapidly over the last decade thanks to the flourishing of large-scale astrometric, photometric and spectroscopic surveys. We emphasise that the primeval stellar populations in the ETDs provide a unique laboratory to study the physical conditions on small scales at epochs beyond z = 2. We highlight the observed diversity of star-formation and chemical enrichment histories in nearby dwarfs. These data can not yet be fully deciphered to reveal the key processes in the dwarf evolution but the first successful attempts have been made to pin down the sites of heavy element production.

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The imprint of bursty star formation on alpha-element abundance patterns in Milky Way-like galaxies

Parul

Bailin

Wetzel

et al. 2023

Monthly Notices of the Royal Astronomical Society

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Milky Way-mass galaxies in the FIRE-2 simulations demonstrate two main modes of star formation. At high redshifts star formation occurs in a series of short and intense bursts, while at low redshifts star formation proceeds at a steady rate with a transition from one mode to another at times ranging from 3 to 7 Gyr ago for different galaxies. We analyse how the mode of star formation affects iron and alpha-element abundance. We find that the early bursty regime imprints a measurable pattern in stellar elemental abundances in the form of a ”sideways chevron” shape on the [Fe/H] - [O/Fe] plane and the scatter in [O/Fe] at a given stellar age is higher than when a galaxy is in the steady regime. That suggests that the evolution of [O/Fe] scatter with age provides an estimate of the end of the bursty phase. We investigate the feasibility of observing of this effect by adding mock observational errors to a simulated stellar survey and find that the transition between the bursty and steady phase should be detectable in the Milky Way, although larger observational uncertainties make the transition shallower. We apply our method to observations of the Milky Way from the Second APOKASC Catalog and estimate that the transition to steady star formation in the Milky Way happened 7-8 Gyrs ago, earlier than transition times measured in the simulations.

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From dawn till disk: Milky Way's turbulent youth revealed by the APOGEE+Gaia data

Cited by 8 publications

References 185 publications

Birth of the Galactic Disk Revealed by the H3 Survey

Birth of the Galactic Disk Revealed by the H3 Survey

Chemical and stellar properties of early-type dwarf galaxies around the Milky Way

The imprint of bursty star formation on alpha-element abundance patterns in Milky Way-like galaxies

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