Merger-induced galaxy transformations in the <scp>artemis</scp> simulations

M., Dillamore, Adam; Belokurov, Vasily; Font, Andreea S.; McCarthy, Ian G.

doi:10.1093/mnras/stac1038

Cited by 36 publications

(38 citation statements)

References 125 publications

(189 reference statements)

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“…Furthermore, these HAC/VOD analogs persist over several gigayears, which is consistent with the observationally inferred timeline of the GSE merger. Lastly, the dark matter contribution from GSE is ∼20% within r gal < 30 kpc in this simulation, which is consistent with hydrodynamical simulations of GSE-like major mergers in MW-like galaxies (Fattahi et al 2019;Dillamore et al 2021).…”

Section: Introductionsupporting

confidence: 88%

“…For example, Emami et al (2021) report that only 32% of Milky Way-like galaxies in the Illustris TNG50 simulation (Nelson et al 2019;Pillepich et al 2019) show simple DM halos, and the rest of the sample exhibit either twisted (gradually rotating) or stretched (abruptly rotating) halos. Prada et al (2019) find that 20% of Milky Way-like galaxies in the Auriga project (Grand et al 2017;Monachesi et al 2019) have twisted halos, while Dillamore et al (2021) find that most galaxies in the ARTEMIS simulations (Font et al 2020) that show GSE-like features exhibit a global change in orientation of their DM halo. In EAGLE simulations (Crain et al 2015;Schaye et al 2015), Shao et al (2021) find that the DM halo of galaxies are well aligned with the common orbital plane of their satellite galaxies.…”

Section: Discussionmentioning

confidence: 99%

“…First, observations of the stellar halo suggest a large-scale tilt on the relevant scales of r gal ∼ 30 kpc, hinting that the DM halo may embody a similar tilt. Second, cosmological simulations show that it is common for DM halos in MW-like galaxies to exhibit nonspherical shapes that are misaligned with the disk (e.g., Prada et al 2019;Emami et al 2021;Dillamore et al 2021) for a variety of reasons linked to their accretion history. In the Galaxy, such a diskhalo misalignment has been proposed to explain the stability of the Sagittarius stream (Debattista et al 2013) or the coplanar orbits of Galaxy's satellites (Shao et al 2021).…”

Section: Introductionmentioning

confidence: 99%

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A Tilt in the Dark Matter Halo of the Galaxy

Han

Naidu

Conroy

et al. 2022

ApJ

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Recent observations of the stellar halo have uncovered the debris of an ancient merger, Gaia–Sausage–Enceladus (GSE), estimated to have occurred ≳8 Gyr ago. Follow-up studies have associated GSE with a large-scale tilt in the stellar halo that links two well-known stellar overdensities in diagonally opposing octants of the Galaxy (the Hercules–Aquila Cloud and Virgo Overdensity; HAC and VOD). In this paper, we study the plausibility of such unmixed merger debris persisting over several gigayears in the Galactic halo. We employ the simulated stellar halo from Naidu et al., which reproduces several key properties of the merger remnant, including the large-scale tilt. By integrating the orbits of these simulated stellar halo particles, we show that adoption of a spherical halo potential results in rapid phase mixing of the asymmetry. However, adopting a tilted halo potential preserves the initial asymmetry in the stellar halo for many gigayears. The asymmetry is preserved even when a realistic growing disk is added to the potential. These results suggest that HAC and VOD are long-lived structures that are associated with GSE and that the dark matter halo of the Galaxy is tilted with respect to the disk and aligned in the direction of HAC–VOD. Such halo–disk misalignment is common in modern cosmological simulations. Lastly, we study the relationship between the local and global stellar halo in light of a tilted global halo comprised of highly radial orbits. We find that the local halo offers a dynamically biased view of the global halo due to its displacement from the Galactic center.

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Section: Introductionsupporting

confidence: 88%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Tilt in the Dark Matter Halo of the Galaxy

Han

Naidu

Conroy

et al. 2022

ApJ

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“…These modeling attempts agree that the dwarf's SFH was shut down between 8 and 10 Gyr ago. Finally, both the progenitor mass and the accretion time can be gauged by comparing the observed redshift z = 0 properties of the tidal debris cloud with its numerical counterparts in galaxy formation simulations (see Belokurov et al 2018;Bignone et al 2019;Fattahi et al 2019;Elias et al 2020;Dillamore et al 2022). Across different simulation suites, these studies find that the accretion events that lead to creation of a highly radially anisotropic metal-rich stellar halo structure near the Sun typically take place 7-10 Gyr ago and that the progenitor galaxies bring between 10 8 and 10 9 M e of stars.…”

Section: Introductionmentioning

confidence: 99%

Milky Way's Eccentric Constituents with Gaia, APOGEE, and GALAH

Belokurov

Aguado

Evans

et al. 2022

ApJ

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We report the results of an unsupervised decomposition of the local stellar halo in the chemodynamical space spanned by the abundance measurements from APOGEE DR17 and GALAH DR3. In our Gaussian mixture model, only four independent components dominate the halo in the solar neighborhood, three previously known, Aurora, Splash, and Gaia-Sausage/Enceladus (GS/E), and one new, Eos. Only one of these four is of accreted origin, namely, the GS/E, thus supporting the earlier claims that the GS/E is the main progenitor of the Galactic stellar halo. We show that Aurora is entirely consistent with the chemical properties of the so-called Heracles merger. In our analysis in which no predefined chemical selection cuts are applied, Aurora spans a wide range of [Al/Fe] with a metallicity correlation indicative of a fast chemical enrichment in a massive galaxy, the young Milky Way. The new halo component dubbed Eos is classified as in situ given its high mean [Al/Fe]. Eos shows strong evolution as a function of [Fe/H], where it changes from being the closest to GS/E at its lowest [Fe/H] to being indistinguishable from the Galactic low-α population at its highest [Fe/H]. We surmise that at least some of the outer thin disk of the Galaxy started its evolution in the gas polluted by the GS/E, and Eos is evidence of this process.

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“…For instance, pure N-body models (Koppelman et al 2020;Naidu et al 2021) constrained the GSE dwarf to be on a retrograde orbit (with respect to the MW's disk rotation) with low-tointermediate circularity, and with a low-inclination angle between its orbital plane and the MW's disk plane. GSE-like mergers have also been identified/studied in cosmological simulations of MW-like galaxies (e.g., Bignone et al 2019;Fattahi et al 2019;Mackereth et al 2019;Elias et al 2020;Grand et al 2020;Dillamore et al 2022). For example, Fattahi et al (2019) selected MW-like galaxies in Auriga (Grand et al 2017) and found that about one-third of them have a highly anisotropic, metal-rich, [Fe/H] ≈ −1, stellar halo, which becomes isotropic at lower metallicities, i.e., just as is observed in the MW.…”

Section: Introductionmentioning

confidence: 99%

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

Amarante

Debattista

Silva

et al. 2022

ApJ

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The Milky Way (MW) stellar halo contains relics of ancient mergers that tell the story of our galaxy's formation. Some of them are identified due to their similarity in energy, actions, and chemistry, referred to as the "chemodynamical space," and are often attributed to distinct merger events. It is also known that our galaxy went through a significant merger event that shaped the local stellar halo during its first billion years. Previous studies using N-body only and cosmological hydrodynamical simulations have shown that such a single massive merger can produce several "signatures" in the chemodynamical space, which can potentially be misinterpreted as distinct merger events. Motivated by these, in this work we use a subset of the GASTRO library, which consists of several smoothed particle hydrodynamics+N-body models of a single accretion event in a MW-like galaxy. Here, we study models with orbital properties similar to the main merger event of our galaxy and explore the implications to known stellar halo substructures. We find that (i) supernova feedback efficiency influences the satellite's structure and orbital evolution, resulting in distinct chemodynamical features for models with the same initial conditions; (ii) very retrograde high-energy stars are the most metal-poor of the accreted dwarf galaxy and could be misinterpreted as a distinct merger; (iii) the most bound stars are more metal-rich in our models, the opposite of what is observed in the MW, suggesting a secondary massive merger; and, finally, (iv) our models can reconcile other known apparently distinct substructures to a unique progenitor.Unified Astronomy Thesaurus concepts: Milky Way dynamics (1051); Milky Way formation (1053); Milky Way stellar halo (1060); Hydrodynamical simulations (767)

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Merger-induced galaxy transformations in the artemis simulations

Cited by 36 publications

References 125 publications

A Tilt in the Dark Matter Halo of the Galaxy

A Tilt in the Dark Matter Halo of the Galaxy

Milky Way's Eccentric Constituents with Gaia, APOGEE, and GALAH

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

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