The chemical characterization of halo substructure in the Milky Way based on APOGEE

Horta, Danny; Schiavon, Ricardo P.; Mackereth, J. Ted; Weinberg, David H.; Hasselquist, Sten; Feuillet, Diane; O’Connell, R. W.; Anguiano, Borja; Allende-Prieto, Carlos; Beaton, Rachael L.; Bizyaev, Dmitry; Cunha, Kátia; Geisler, Doug; García–Hernández, D. A.; Holtzman, Jon A.; Jönsson, Henrik; Majewski, S. R.; Mészáros, Szabolcs; Minniti, D.; Nitschelm, Christian; Shetrone, M.; Smith, Verne V.; Zasowski, Gail

doi:10.1093/mnras/stac3179

Cited by 59 publications

(43 citation statements)

References 153 publications

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“…On the chemical-abundance front, SEGUE data allowed us to verify that the [α/Fe] of the Sgr stream decreases with increasing [Fe/H]. Most important, at a given metallicity, we ascertained that the median [α/Fe] of the Sgr stream is lower than GSE's, in conformity with other recent efforts (Hasselquist et al 2021;Limberg et al 2022;Horta et al 2023). 8.…”

Section: Discussionsupporting

confidence: 83%

“…stein 1962;Tinsley 1979) for this substructure. However, this result is not supported by contemporaneous high-resolution spectroscopic data, especially from APOGEE (Hayes et al 2020;Limberg et al 2022;Horta et al 2023), also H3 (Johnson et al 2020;Naidu et al 2020). If the position of Sgr's α knee was truly located at such high [Fe/H], it would imply that it should be even more massive than GSE under standard chemical-evolution prescriptions (e.g., Matteucci & Brocato 1990).…”

Section: Sgr Dsph Before Its Disruptionmentioning

confidence: 86%

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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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Section: Discussionsupporting

confidence: 83%

Section: Sgr Dsph Before Its Disruptionmentioning

confidence: 86%

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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“…Horta et al (2021) applied the same idea for a star sample located in the Galactic centre to find debris stars within the Galactic bulge. They called this inner Galaxy structure placed in the ex-situ portion of the [Mg/Mn]-[Al/Fe] plane Heracles and defined it as follows (Horta et al 2022): for Pal 6 members, because this cluster is located perfectly in the high-α region. In contrast, the NGC 6355 is located at the border between Heracles and the in-situ high-α region.…”

Section: Analysis Of Abundance Discriminatorsmentioning

confidence: 99%

Chrono-chemodynamical analysis of the globular cluster NGC 6355: Looking for the fundamental bricks of the Bulge

Souza

Ernandes

Valentini

et al. 2023

A&A

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The information on Galactic assembly time is imprinted on the chemodynamics of globular clusters. This makes them important probes that help us to understand the formation and evolution of the Milky Way. Discerning between in-situ and ex-situ origin of these objects is difficult when we study the Galactic bulge, which is the most complex and mixed component of the Milky Way. To investigate the early evolution of the Galactic bulge, we analysed the globular cluster NGC 6355. We derived chemical abundances and kinematic and dynamic properties by gathering information from high-resolution spectroscopy with FLAMES-UVES, photometry with the Hubble Space Telescope, and Galactic dynamic calculations applied to the globular cluster NGC 6355. We derive an age of 13.2 ± 1.1 Gyr and a metallicity of [Fe/H] = − 1.39 ± 0.08 for NGC 6355, with α-enhancement of [α/Fe] = + 0.37 ± 0.11. The abundance pattern of the globular cluster is compatible with bulge field RR Lyrae stars and in-situ well-studied globular clusters. The orbital parameters suggest that the cluster is currently confined within the bulge volume when we consider a heliocentric distance of 8.54 ± 0.19 kpc and an extinction coefficient of RV = 2.84 ± 0.02. NGC 6355 is highly likely to come from the main bulge progenitor. Nevertheless, it still has a low probability of being formed from an accreted event because its age is uncertain and because of the combined [Mg/Mn] [Al/Fe] abundance. Its relatively low metallicity with respect to old and moderately metal-poor inner Galaxy clusters may suggest a low-metallicity floor for globular clusters that formed in-situ in the early Galactic bulge.

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“…This contamination by disk stars is further enhanced by the existence of "Splash" stars, which are early disk stars whose orbits were perturbed by the collision with GE/S (Belokurov et al 2020). For a discussion of the impact of selection criteria on the chemical properties of GE/S, see Horta et al (2022b).…”

Section: Sagittarius Dsph Galaxymentioning

confidence: 99%

“…Chemical compositions and orbital information is becoming available for millions of stars in the MW and its Local Group companions. In addition, with the launching of the Gaia satellite (Gaia Collaboration et al 2016), detailed phase space information has become available, enabling the identification of further substructures in the stellar halo of the Galaxy, associated with various accretion events, including Gaia-Enceladus/Sausage, a massive dwarf galaxy accreted to the MW about ∼10Gyr ago (Belokurov et al 2018;Haywood et al 2018;Helmi et al 2018;Mackereth et al 2019), as well as Heracles (Horta et al 2021a), and various other substructures (e.g., Koppelman et al 2019a;Belokurov et al 2018;Kruĳssen et al 2020;Naidu et al 2020;Horta et al 2022a). Hawkins et al (2015) and Das et al (2020) have recently proposed that a combination of the abundances of Mn, Mg, Al, and Fe can be used to chemically discriminate accreted populations from their counterparts formed in situ.…”

Section: Introductionmentioning

confidence: 99%

A Comparative Analysis of the Chemical Compositions of Gaia-Enceladus/Sausage and Milky Way Satellites using APOGEE

Fernandes¹,

Mason²,

Horta³

et al. 2023

Preprint

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We use data from the 17 th data release of the Apache Point Observatory Galactic Evolution Experiment (APOGEE 2) to contrast the chemical composition of the recently discovered Gaia Enceladus/Sausage system (GE/S) to those of ten Milky Way (MW) dwarf satellite galaxies: LMC, SMC, Boötes I, Carina, Draco, Fornax, Sagittarius, Sculptor, Sextans and Ursa Minor. Our main focus is on the distributions of the stellar populations of those systems in the [Mg/Fe]-[Fe/H] and [Mg/Mn]-[Al/Fe] planes, which are commonly employed in the literature for chemical diagnosis and where dwarf galaxies can be distinguished from in situ populations. We show that, unlike MW satellites, a GE/S sample defined purely on the basis of orbital parameters falls almost entirely within the locus of "accreted" stellar populations in chemical space, which is likely caused by an early quenching of star formation in GE/S. Due to a more protracted history of star formation, stars in the metal-rich end of the MW satellite populations are characterized by lower [Mg/Mn] than those of their GE/S counterparts. The chemical compositions of GE/S stars are consistent with a higher early star formation rate than MW satellites of comparable and even higher mass, suggesting that star formation in the early universe was strongly influenced by other parameters in addition to mass. We find that the direction of the metallicity gradient in the [Mg/Mn]-[Al/Fe] plane of dwarf galaxies is an indicator of the early star formation rate of the system.

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The chemical characterization of halo substructure in the Milky Way based on APOGEE

Cited by 59 publications

References 153 publications

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

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

Chrono-chemodynamical analysis of the globular cluster NGC 6355: Looking for the fundamental bricks of the Bulge

A Comparative Analysis of the Chemical Compositions of Gaia-Enceladus/Sausage and Milky Way Satellites using APOGEE

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