The Information Content of Stellar Halos: Stellar Population Gradients and Accretion Histories in Early-Type Illustris Galaxies

Cook, B. A.; Conroy, Charlie; Pillepich, Annalisa; Rodríguez-Gómez, Vicente; Hernquist, Lars

doi:10.3847/1538-4357/833/2/158

Cited by 74 publications

(117 citation statements)

References 105 publications

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“…Greene et al 2015;McDermid et al 2015; Barone et al 2018;Ferreras et al 2019). This is consistent with the cosmological simulations of the massive ETGs that predict different metallicity profiles as function of the mass assembly history, with shallower profiles in the outskirts when repeated mergers occur (Cook et al 2016).…”

Section: Introductionsupporting

confidence: 90%

The Fornax3D project: Tracing the assembly history of the cluster from the kinematic and line-strength maps

Iodice

Sarzi

Bittner

et al. 2019

A&A

186

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The 31 brightest galaxies (m B ≤ 15 mag) inside the virial radius of the Fornax cluster were observed from the centres to the outskirts with the Multi Unit Spectroscopic Explorer on the Very Large Telescope. These observations provide detailed high-resolution maps of the line-of-sight kinematics and line strengths of the stars and ionised gas reaching 2-3 R e for 21 early-type galaxies and 1-2 R e for 10 late-type galaxies. The majority of the galaxies are regular rotators, with eight hosting a kinematically distinct core. Only two galaxies are slow rotators. The mean age, total metallicity, and [Mg/Fe] abundance ratio in the bright central region inside 0.5R e and in the galaxy outskirts are presented. Extended emission-line gas is detected in 13 galaxies, most of them are late-type objects with wide-spread star formation. The measured structural properties are analysed in relation to the galaxies' position in the projected phase space of the cluster. This shows that the Fornax cluster appears to consist of three main groups of galaxies inside the virial radius: the old core; a clump of galaxies, which is aligned with the local large-scale structure and was accreted soon after the formation of the core; and a group of galaxies that fell in more recently.

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Section: Introductionsupporting

confidence: 90%

The Fornax3D project: Tracing the assembly history of the cluster from the kinematic and line-strength maps

Iodice

Sarzi

Bittner

et al. 2019

A&A

186

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“…The CRC in NGC 3522 has a peak rotation of only about 20 km/s and is located within the central 5 tions (e.g. Dubois et al 2013;Hirschmann et al 2015;Cook et al 2016) Notwithstanding the details and the absolute level of predicted metallicity gradients by models, a general conclusion is that galaxies undergoing dissipation-less merging will have flatter gradients than galaxies that experience gas-rich mergers or secondary star formation of any origin. This is important because we can link these predictions with formation scenarios for galaxies with cores (gas-poor major mergers) or for those with core-less light profiles (gas-rich mergers followed by a nuclear starburst).…”

Section: Formation Of Flat Metallicity Gradientsmentioning

confidence: 99%

“…Massive galaxies are gas-poor systems, and their late evolution (z < 2) is dominated by accretion of stars formed elsewhere (e.g. De Lucia & Blaizot 2007;Oser et al 2010;Wellons et al 2015;Cook et al 2016;Lagos et al 2018). The current picture is that low-mass galaxies typically grow through star formation and are more likely to experience dissipative mergers, while massive galaxies accrete stars formed elsewhere and grow through dissipation-less mergers (e.g.…”

Section: Formation Of Slow Rotators With and Without Coresmentioning

confidence: 99%

Formation channels of slowly rotating early-type galaxies

Krajnović

Ural

Küntschner

et al. 2020

A&A

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We study the evidence for a diversity of formation processes in early-type galaxies by presenting the first complete volume-limited sample of slow rotators with both integral-field kinematics from the ATLAS 3D Project and high spatial resolution photometry from the Hubble Space Telescope. Analysing the nuclear surface brightness profiles of 12 newly imaged slow rotators, we classify their light profiles as core-less, and place an upper limit to the core size of about 10 pc. Considering the full magnitude and volumelimited ATLAS 3D sample, we correlate the presence or lack of cores with stellar kinematics, including the proxy for the stellar angular momentum (λ Re ) and the velocity dispersion within one half-light radius (σ e ), stellar mass, stellar age, α-element abundance, and age and metallicity gradients. More than half of the slow rotators have core-less light profiles, and they are all less massive than 10 11 M . Core-less slow rotators show evidence for counter-rotating flattened structures, have steeper metallicity gradients, and a larger dispersion of gradient values (∆[Z/H] = −0.42 ± 0.18) than core slow rotators (∆[Z/H] = −0.23 ± 0.07). Our results suggest that core and core-less slow rotators have different assembly processes, where the former, as previously discussed, are the relics of massive dissipation-less merging in the presence of central supermassive black holes. Formation processes of core-less slow rotators are consistent with accretion of counter-rotating gas or gas-rich mergers of special orbital configurations, which lower the final net angular momentum of stars, but support star formation. We also highlight core fast rotators as galaxies that share properties of core slow rotators (i.e. cores, ages, σ e , and population gradients) and core-less slow rotators (i.e. kinematics, λ Re , mass, and larger spread in population gradients). Formation processes similar to those for core-less slow rotators can be invoked to explain the assembly of core fast rotators, with the distinction that these processes form or preserve cores.

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“…The simulation features a physical model of galaxy formation (Vogelsberger et al 2013;Torrey et al 2014) which has been shown to reproduce various galaxy observables, including several which were not used in the calibration of the model (e.g. Sales et al 2015;Wellons et al 2015;Rodriguez-Gomez et al 2015;Genel et al 2015;Mistani et al 2016;Cook et al 2016).…”

Section: The Illustris and Illustris-dark Simulationsmentioning

confidence: 99%

The role of mergers and halo spin in shaping galaxy morphology

Rodríguez-Gómez

Sales

Genel

et al. 2017

Monthly Notices of the Royal Astronomical Society

183

157

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Mergers and the spin of the dark matter halo are factors traditionally believed to determine the morphology of galaxies within a ΛCDM cosmology. We study this hypothesis by considering approximately 18,000 central galaxies at z = 0 with stellar masses M * = 10 9 -10 12 M selected from the Illustris cosmological hydrodynamic simulation. The fraction of accreted stars -which measures the importance of massive, recent and dry mergers -increases steeply with galaxy stellar mass, from less than 5 per cent in dwarfs to 80 per cent in the most massive objects, and the impact of mergers on galaxy morphology increases accordingly. For galaxies with M * 10 11 M , mergers have the expected effect: if gas-poor they promote the formation of spheroidal galaxies, whereas gas-rich mergers favour the formation and survivability of massive discs. This trend, however, breaks at lower masses. For objects with M * 10 11 M , mergers do not seem to play any significant role in determining the morphology, with accreted stellar fractions and mean merger gas fractions that are indistinguishable between spheroidal and disc-dominated galaxies. On the other hand, halo spin correlates with morphology primarily in the least massive objects in the sample (M * 10 10 M ), but only weakly for galaxies above that mass. Our results support a scenario where (1) mergers play a dominant role in shaping the morphology of massive galaxies, (2) halo spin is important for the morphology of dwarfs, and (3) the morphology of medium-sized galaxies -including the Milky Way -shows little dependence on galaxy assembly history or halo spin, at least when these two factors are considered individually.

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The Information Content of Stellar Halos: Stellar Population Gradients and Accretion Histories in Early-Type Illustris Galaxies

Cited by 74 publications

References 105 publications

The Fornax3D project: Tracing the assembly history of the cluster from the kinematic and line-strength maps

The Fornax3D project: Tracing the assembly history of the cluster from the kinematic and line-strength maps

Formation channels of slowly rotating early-type galaxies

The role of mergers and halo spin in shaping galaxy morphology

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