The Pristine Inner Galaxy Survey (PIGS) – IV. A photometric metallicity analysis of the Sagittarius dwarf spheroidal galaxy

Vitali, Sara; Arentsen, Anke; Starkenburg, Else; Jofré, P.; Martín, Nicolás F.; Aguado, David S.; Carlberg, R. G.; Hernández, J. I. González; Ibata, Rodrigo; Kordopatis, G.; Malhan, Khyati; Ramos, P.; Sestito, Federico; Yuan, Zhen; Buder, Sven; Lewis, Geraint F.; Wan, Zhen; Zucker, Daniel B.

doi:10.1093/mnras/stac2869

Cited by 8 publications

(4 citation statements)

References 96 publications

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“…Therefore, with the understanding that the old wrap is essentially composed of low-metallicity stars), we reach the conclusion that the core regions of the Sgr dSph were more metal-rich than its outskirts prior to its accretion. We recall that, indeed, previous works reported evidence for a metallicity gradient in the Sgr remnant (Bellazzini et al 1999;Layden & Sarajedini 2000;Siegel et al 2007;McDonald et al 2013;Mucciarelli et al 2017;Vitali et al 2022). Nevertheless, fully understanding how these stellar-population variations in the Sgr system relate to its interaction with the Milky Way remains to be seen (for example, via induced star formation bursts; Hasselquist et al 2021).…”

Section: Sgr Dsph Before Its Disruptionsupporting

confidence: 65%

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: Sgr Dsph Before Its Disruptionsupporting

confidence: 65%

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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“…The resulting cross-matched sample shown Figures 1, 2, and 3 consists of 34,240 stars. This sample is larger than previous samples of stars with chemical abundance estimates in the Sgr stream by an order of magnitude (though we note that there are large samples of Sgr main-body stars that have estimates from photometric metallicities; e.g., Vitali et al 2022). The Sgr main body can be seen in Figure 1 at (Λ, B) = (Λ 0 , B 0 ) ∼ (0 deg, 1.5 deg); there is a local peak in the metallicity map at the core of ∼−0.8 dex, and the mean metallicity visibly decreases in both coordinates as we move away from the center of the main body.…”

Section: Abundances From Gaia Xp Spectramentioning

confidence: 85%

“…Finally, most studies of metallicity in the Sgr stream have focused on trends with stream longitude (along the stream), and not with stream latitude (across the stream). While a gradient across the core has been observed (Vitali et al 2022), and metallicity differences have been observed in the different branches of the stream (Ramos et al 2022), no gradient has been detected across the Sgr stream. However, a gradient perpendicular to the stream track has been detected in Andromeda's Giant Stellar Stream (Ibata et al 2007;Escala et al 2021).…”

Section: Introductionmentioning

confidence: 94%

“…As samples grew, chemical differences along the different arms of the stream were observed (e.g., Keller et al 2010;Carlin et al 2012Carlin et al , 2018Shi et al 2012;Hyde et al 2015;Hasselquist et al 2019;Yang et al 2019;Hayes et al 2020;Zhao et al 2020;Ramos et al 2022). Several studies have argued that there is a metallicity gradient in the core (e.g., Majewski et al 2013;Mucciarelli et al 2017;Vitali et al 2022;Minelli et al 2023). Other works have argued in favor of an initial metallicity gradient based on the radial velocity dispersions of stream stars in different metallicity bins (e.g., Gibbons et al 2017;Johnson et al 2020;Limberg et al 2023).…”

Section: Introductionmentioning

confidence: 99%

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Chemical Cartography of the Sagittarius Stream with Gaia

Cunningham,

Hunt,

Price-Whelan

et al. 2024

ApJ

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The stellar stream connected to the Sagittarius (Sgr) dwarf galaxy is the most massive tidal stream that has been mapped in the Galaxy, and is the dominant contributor to the outer stellar halo of the Milky Way (MW). We present metallicity maps of the Sgr stream, using 34,240 red giant branch stars with inferred metallicities from Gaia BP/RP spectra. This sample is larger than previous samples of Sgr stream members with chemical abundances by an order of magnitude. We measure metallicity gradients with respect to Sgr stream coordinates (Λ, B), and highlight the gradient in metallicity with respect to stream latitude coordinate B, which has not been observed before. Including the core, we find ∇[M/H] = −2.48 ± 0.08 × 10−2 dex deg−1 above the stream track (B > B 0, where B 0 = 1.5° is the latitude of the Sgr remnant) and ∇[M/H] = −2.02 ± 0.08 × 10−2 dex deg−1 below the stream track (B < B 0). By painting metallicity gradients onto a tailored N-body simulation of the Sgr stream, we find that the observed metallicities in the stream are consistent with an initial radial metallicity gradient in the Sgr dwarf galaxy of ∼−0.1 to −0.2 dex kpc−1, well within the range of observed metallicity gradients in Local Group dwarf galaxies. Our results provide novel observational constraints for the internal structure of the dwarf galaxy progenitor of the Sgr stream. Leveraging new large data sets in conjunction with tailored simulations, we can connect the present-day properties of disrupted dwarfs in the MW to their initial conditions.

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The metallicity distribution in the core of the Sagittarius dwarf spheroidal: Minimising the metallicity biases

Minelli

Bellazzini²,

Mucciarelli

et al. 2023

A&A

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We present metallicity and radial velocity for 450 bona-fide members of the Sagittarius dwarf spheroidal (Sgr dSph) galaxy, measured from high resolution (R 18000) FLAMES@VLT spectra. The targets were carefully selected (a) to sample the core of the main body of Sgr dSph while avoiding contamination from the central stellar nucleus, and (b) to prevent any bias on the metallicity distribution, by selecting targets based on their Gaia parallax and proper motions. All the targets selected in this way were confirmed as radial velocity members. We used this sample to derive the first metallicity distribution of the core of the Sgr dSph virtually unaffected by metallicity biases. The observed distribution ranges from [Fe/H] −2.3 to [Fe/H] 0.0, with a strong, symmetric and relatively narrow peak around [Fe/H] −0.5 and a weak, extended metal-poor tail, with only 13.8 ± 1.9% of the stars having [Fe/H]< −1.0. We confirm previous evidence of correlations between chemical and kinematical properties of stars in the core of Sgr. In our sample stars with [Fe/H]≥ −0.6 display a lower velocity dispersion and a higher rotation amplitude than those with [Fe/H]< −0.6, confirming previous suggestions of a disk/halo structure for the progenitor of the system.

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The Pristine Inner Galaxy Survey (PIGS) – IV. A photometric metallicity analysis of the Sagittarius dwarf spheroidal galaxy

Cited by 8 publications

References 96 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

Chemical Cartography of the Sagittarius Stream with Gaia

The metallicity distribution in the core of the Sagittarius dwarf spheroidal: Minimising the metallicity biases

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