The distinct stellar metallicity populations of simulated Local Group dwarfs

Genina, Anna; Frenk, Carlos S.; Benitez-Llambay, Alejand ro; Cole, Shaun; Navarro, Julio F.; Oman, Kyle A.; Fattahi, Azadeh

doi:10.1093/mnras/stz1852

Cited by 35 publications

(46 citation statements)

References 72 publications

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Section: H E M O Dy Na M I C P O P U L At I O N S T H Ro U G H O U mentioning

confidence: 84%

“…is smaller in satellites, likely due to tidal stripping (Genina et al 2018(Genina et al , 2019. At the lowest stellar masses, Genina et al (2019) find that most multiple populations in dSphs are primarily formed due to mergers. Observations of prolate rotation may be evidence for past mergers (Amorisco et al 2014;Kacharov et al 2017) and the two populations in UMi could be evidence for a late-time merger.…”

Section: H E M O Dy Na M I C P O P U L At I O N S T H Ro U G H O U mentioning

confidence: 84%

“…Several formation scenarios for multiple populations have been proposed, including mergers (Amorisco & Evans 2012b;del Pino, Aparicio & Hidalgo 2015;Genina et al 2019), supernova feedback (Salvadori, Ferrara & Schneider 2008;Revaz et al 2009), tidal interactions (Pasetto et al 2011), interactions with a gaseous cosmic filament (Genina et al 2019), or compression of gas during infall (Genina et al 2019). In addition, they are seen in isolated hydrodynamical simulations (Revaz & Jablonka 2018).…”

Section: H E M O Dy Na M I C P O P U L At I O N S T H Ro U G H O U mentioning

confidence: 99%

“…In addition, they are seen in isolated hydrodynamical simulations (Revaz & Jablonka 2018). In the merger scenario, the spatial separation is due to metal-poor stars migrating to outer orbits with the metal-rich population forming in situ after the merger (Genina et al 2019). Based on Gaia DR2 proper motions, the infall time of UMi is 10.7 Gyr (Fillingham et al 2019) and is early enough that the metal-rich population could have formed due to gas compression from ram pressure stripping during MW infall.…”

Section: H E M O Dy Na M I C P O P U L At I O N S T H Ro U G H O U mentioning

confidence: 99%

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Multiple chemodynamic stellar populations of the Ursa Minor dwarf spheroidal galaxy

Pace

Kaplinghat

Kirby

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We present a Bayesian method to identify multiple (chemodynamic) stellar populations in dwarf spheroidal galaxies (dSphs) using velocity, metallicity, and positional stellar data without the assumption of spherical symmetry. We apply this method to a new Keck/Deep Imaging Multi-Object Spectrograph (DEIMOS) spectroscopic survey of the Ursa Minor (UMi) dSph. We identify 892 likely members, making this the largest UMi sample with line-of-sight velocity and metallicity measurements. Our Bayesian method detects two distinct chemodynamic populations with high significance (in logarithmic Bayes factor, ln B ∼ 33). The metal-rich ([Fe/H] = −2.05 ± 0.03) population is kinematically colder (radial velocity dispersion of $\sigma _v=4.9_{-1.0}^{+0.8} \, \mathrm{km} \, \mathrm{s}^{-1}$) and more centrally concentrated than the metal-poor ($[{\rm Fe/H}]=-2.29_{-0.06}^{+0.05}$) and kinematically hotter population ($\sigma _v =11.5_{-0.8}^{+0.9}\, \mathrm{km} \, \mathrm{s}^{-1}$). Furthermore, we apply the same analysis to an independent Multiple Mirror Telescope (MMT)/Hectochelle data set and confirm the existence of two chemodynamic populations in UMi. In both data sets, the metal-rich population is significantly flattened (ϵ = 0.75 ± 0.03) and the metal-poor population is closer to spherical ($\epsilon =0.33_{-0.09}^{+0.12}$). Despite the presence of two populations, we are able to robustly estimate the slope of the dynamical mass profile. We found hints for prolate rotation of order ${\sim}2 \, \mathrm{km} \, \mathrm{s}^{-1}$ in the MMT data set, but further observations are required to verify this. The flattened metal-rich population invalidates assumptions built into simple dynamical mass estimators, so we computed new astrophysical dark matter annihilation (J) and decay profiles based on the rounder, hotter metal-poor population and inferred $\log _{10}{(J(0{^{\circ}_{.}}5)/{\rm GeV^{2} \, cm^{-5}})}\approx 19.1$ for the Keck data set. Our results paint a more complex picture of the evolution of UMi than previously discussed.

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Section: H E M O Dy Na M I C P O P U L At I O N S T H Ro U G H O U mentioning

confidence: 84%

Section: H E M O Dy Na M I C P O P U L At I O N S T H Ro U G H O U mentioning

confidence: 84%

Section: H E M O Dy Na M I C P O P U L At I O N S T H Ro U G H O U mentioning

confidence: 99%

Section: H E M O Dy Na M I C P O P U L At I O N S T H Ro U G H O U mentioning

confidence: 99%

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Multiple chemodynamic stellar populations of the Ursa Minor dwarf spheroidal galaxy

Pace

Kaplinghat

Kirby

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…Some of these differences could indicate an ancient merger, which would have dispersed the old stellar component and allowed the enriched gas to sink further in before forming stars (Benítez-Llambay et al 2016;Genina et al 2019). This would provide a plausible explanation for the radial offset between the original distribution of Fornax GCs and the present-day distributions of its stars.…”

Section: Discussionmentioning

confidence: 99%

Cusp or core? Revisiting the globular cluster timing problem in Fornax

Meadows

Navarro

Santos-Santos

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We use N-body simulations to revisit the globular cluster (GC) "timing problem" in the Fornax dwarf spheroidal (dSph). In agreement with earlier work, we find that, due to dynamical friction, GCs sink to the center of dark matter halos with a cuspy inner density profile but "stall" at roughly 1/3 of the core radius (r core ) in halos with constant-density cores. The timescales to sink or stall depend strongly on the mass of the GC and on the initial orbital radius, but are essentially the same for either cuspy (NFW) or cored halos normalized to have the same total mass within r core . Arguing against a cusp on the basis that GCs have not sunk to the center is thus no different from arguing against a core, unless all clusters are today at ∼ (1/3) r core . This would imply a core radius exceeding ∼ 3 kpc, much larger than seems plausible in any core-formation scenario. (The average projected distance of Fornax GCs is R GC,Fnx ∼ 1 kpc and its effective radius is ∼ 700 pc.) A simpler explanation is that Fornax GCs have only been modestly affected by dynamical friction, as expected if clusters started orbiting at initial radii of order ∼ 1-2 kpc, just outside Fornax's present-day half-light radius but well within the tidal radius imprinted by Galactic tides. This is not entirely unexpected. Fornax GCs are significantly older and more metal-poor than most Fornax stars, and such populations in dSphs tend to be more spatially extended than their younger and more metal-rich counterparts. Contrary to some earlier claims, our simulations further suggest that GCs do not truly "stall" at ∼ 0.3 r core , but rather continue decaying toward the center, albeit at reduced rates. We conclude that dismissing the presence of a cusp in Fornax based on the spatial distribution of its GC population is unwarranted.

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The Fornax3D project: Environmental effects on the assembly of dynamically cold disks in Fornax cluster galaxies

Ding

Zhu

Ven

et al. 2023

A&A

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We apply a population-orbit superposition metho1d to 16 galaxies in the Fornax cluster observed with MUSE/VLT in the context of the Fornax3D project. By fitting the luminosity distribution, stellar kinematics, and age and metallicity maps simultaneously, we obtained the internal stellar orbit distribution, as well as the age and metallicity distribution of stars on different orbits for each galaxy. Based on the model, we decompose each galaxy into a dynamically cold disk (orbital circularity λz ≥ 0.8) and a dynamically hot non-disk component (orbital circularity λz < 0.8), and obtain the surface-brightness, age, and metallicity radial profiles of each component. The galaxy infall time into the cluster is strongly correlated with galaxy cold-disk age with older cold disks in ancient infallers. We quantify the infall time tinfall of each galaxy with its cold-disk age using a correlation calibrated with TNG50 cosmological simulations. For galaxies in the Fornax cluster, we found that the luminosity fraction of cold disk in galaxies with tinfall > 8 Gyr are a factor of ∼4 lower than in more recent infallers while controlling for total stellar mass. Nine of the 16 galaxies have spatially extended cold disks, and most of them show positive or zero age gradients; stars in the inner disk are ∼2 − 5 Gyr younger than that in the outer disk, in contrast to the expectation of inside-out growth. Our results indicate that the assembly of cold disks in galaxies is strongly affected by their infall into clusters, by either removal of gas in outer regions or even tidally stripping or heating part of the pre-existing disks. Star formation in outer disks can stop quickly after the galaxy falls into the cluster, while star formation in the inner disks can last for a few Gyrs more, building the positive age gradient measured in cold disks.

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The distinct stellar metallicity populations of simulated Local Group dwarfs

Cited by 35 publications

References 72 publications

Multiple chemodynamic stellar populations of the Ursa Minor dwarf spheroidal galaxy

Multiple chemodynamic stellar populations of the Ursa Minor dwarf spheroidal galaxy

Cusp or core? Revisiting the globular cluster timing problem in Fornax

The Fornax3D project: Environmental effects on the assembly of dynamically cold disks in Fornax cluster galaxies

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