Gastro Library. I. The Simulated Chemodynamical Properties of Several Gaia–Sausage–Enceladus-like Stellar Halos

Amarante, João A. S.; Debattista, Victor P.; Silva, Leandro Beraldo e; Laporte, Chervin F. P.; Deg, Nathan

doi:10.3847/1538-4357/ac8b0d

Cited by 40 publications

(31 citation statements)

References 141 publications

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“…Indeed, Horta et al (2021) acknowledge such stars as a potential source of contamination. To expand upon this, Figure 13 Therefore, stars attributed to Kraken may in fact be in-situ Aurora population stars (and also unlikely to originate from the GSE debris because we would then expect to observe an excess of metal-rich stars towards the bulge, Amarante et al 2022). Such an interpretation is also supported by the recent stellar halo study of Myeong et al (2022).…”

Section: Discussionmentioning

confidence: 66%

The impact of two massive early accretion events in a Milky Way-like galaxy: repercussions for the buildup of the stellar disc and halo

Orkney

Laporte

Grand

et al. 2022

Monthly Notices of the Royal Astronomical Society: Letters

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We identify and characterise a Milky Way-like realisation from the Auriga simulations with two consecutive massive mergers ∼2 Gyr apart at high redshift, comparable to the reported Kraken and Gaia-Sausage-Enceladus. The Kraken-like merger (z = 1.6, $M_{\rm Tot}=8\times 10^{10}\, \rm {M_{\odot }}$) is gas-rich, deposits most of its mass in the inner 10 kpc, and is largely isotropic. The Sausage-like merger (z = 1.14, $M_{\rm Tot}=1\times 10^{11}\, \rm {M_{\odot }}$) leaves a more extended mass distribution at higher energies, and has a radially anisotropic distribution. For the higher-redshift merger, the stellar mass ratio of the satellite to host galaxy is high (1:3). As a result, the chemistry of the remnant is indistinguishable from contemporaneous in-situ populations, making it challenging to identify through chemical abundances. This naturally explains why all abundance patterns attributed so far to Kraken are in fact fully consistent with the metal-poor in-situ so-called Aurora population and thick disc. However, our model makes a falsifiable prediction: if the Milky Way underwent a gas-rich double merger at high redshift, then this should be imprinted on its star formation history with bursts about ∼2 Gyrs apart. This may offer constraining power on the highest-redshift massive mergers.

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Section: Discussionmentioning

confidence: 66%

The impact of two massive early accretion events in a Milky Way-like galaxy: repercussions for the buildup of the stellar disc and halo

Orkney

Laporte

Grand

et al. 2022

Monthly Notices of the Royal Astronomical Society: Letters

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“…Building on the above-described facts, we quantify how useful the J z > J R condition is for eliminating potential GSE contaminants within our Sgr stream members. We look at a suite of chemodynamical simulations of Milky Way-mass galaxies with stellar halos produced by a single GSE-like merger presented in Amarante et al (2022). Within these models, the fraction of GSE debris that end up (at redshift z = 0) on orbits with J z > J R is always below 9%.…”

Section: Selection Of Membersmentioning

confidence: 99%

Phase-space Properties and Chemistry of the Sagittarius Stellar Stream Down to the Extremely Metal-poor ([Fe/H] ≲ −3) Regime

Limberg

Queiroz

Perottoni

et al. 2023

ApJ

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In this work, we study the phase-space and chemical properties of the Sagittarius (Sgr) stream, the tidal tails produced by the ongoing destruction of the Sgr dwarf spheroidal (dSph) galaxy, focusing on its very metal-poor (VMP; [Fe/H] < −2) content. We combine spectroscopic and astrometric information from SEGUE and Gaia EDR3, respectively, with data products from a new large-scale run of the StarHorse spectrophotometric code. Our selection criteria yield ∼1600 stream members, including >200 VMP stars. We find the leading arm (b > 0°) of the Sgr stream to be more metal-poor, by ∼0.2 dex, than the trailing one (b < 0°). With a subsample of turnoff and subgiant stars, we estimate this substructure’s stellar population to be ∼1 Gyr older than the thick disk’s. With the aid of an N-body model of the Sgr system, we verify that simulated particles stripped earlier (>2 Gyr ago) have present-day phase-space properties similar to lower metallicity stream stars. Conversely, those stripped more recently (<2 Gyr) are preferentially akin to metal-rich ([Fe/H] > −1) members of the stream. Such correlation between kinematics and chemistry can be explained by the existence of a dynamically hotter, less centrally concentrated, and more metal-poor population in Sgr dSph prior to its disruption, implying that this galaxy was able to develop a metallicity gradient before its accretion. Finally, we identified several carbon-enhanced metal-poor ([C/Fe] > +0.7 and [Fe/H] ≤ −1.5) stars in the Sgr stream, which might be in tension with current observations of its remaining core where such objects are not found.

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“…Recent observational work has also suggested this is the case for the MW (e.g., Myeong et al 2019;Koppelman et al 2020;Naidu et al 2020). However, the nature of all these recently identified stellar halo populations stills needs to be fully established, as many of the identified halo substructures so far could be the result of one overall ancient massive merger (Amarante et al 2022;Horta et al 2022). As we have seen in Figure 3, disrupted satellites can deposit their stars in a wide range of galactocentric radii, which can also appear fragmented in orbital space (Jean-Baptiste et al 2017; Koppelman et al 2020;Naidu et al 2021).…”

Section: What Do These Results Mean For Future Surveys?mentioning

confidence: 98%

The Observable Properties of Galaxy Accretion Events in Milky Way–like Galaxies in the FIRE-2 Cosmological Simulations

Horta

Cunningham

Sanderson

et al. 2023

ApJ

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In the Λ-Cold Dark Matter model of the universe, galaxies form in part through accreting satellite systems. Previous works have built an understanding of the signatures of these processes contained within galactic stellar halos. This work revisits that picture using seven Milky Way–like galaxies in the Latte suite of FIRE-2 cosmological simulations. The resolution of these simulations allows a comparison of contributions from satellites aboveM * ≳ 10 × 7 M ⊙, enabling the analysis of observable properties for disrupted satellites in a fully self-consistent and cosmological context. Our results show that the time of accretion and the stellar mass of an accreted satellite are fundamental parameters that in partnership dictate the resulting spatial distribution, orbital energy, and [α/Fe]-[Fe/H] compositions of the stellar debris of such mergers at present day. These parameters also govern the resulting dynamical state of an accreted galaxy at z = 0, leading to the expectation that the inner regions of the stellar halo (R GC ≲ 30 kpc) should contain fully phase-mixed debris from both lower- and higher-mass satellites. In addition, we find that a significant fraction of the lower-mass satellites accreted at early times deposit debris in the outer halo (R GC > 50 kpc) that are not fully phased-mixed, indicating that they could be identified in kinematic surveys. Our results suggest that, as future surveys become increasingly able to map the outer halo of our Galaxy, they may reveal the remnants of long-dead dwarf galaxies whose counterparts are too faint to be seen in situ in higher-redshift surveys.

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Gastro Library. I. The Simulated Chemodynamical Properties of Several Gaia–Sausage–Enceladus-like Stellar Halos

Cited by 40 publications

References 141 publications

The impact of two massive early accretion events in a Milky Way-like galaxy: repercussions for the buildup of the stellar disc and halo

The impact of two massive early accretion events in a Milky Way-like galaxy: repercussions for the buildup of the stellar disc and halo

Phase-space Properties and Chemistry of the Sagittarius Stellar Stream Down to the Extremely Metal-poor ([Fe/H] ≲ −3) Regime

The Observable Properties of Galaxy Accretion Events in Milky Way–like Galaxies in the FIRE-2 Cosmological Simulations

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