Super Metal-rich Stars in the LAMOST Survey: A Test on Radial Migration

Chen, Yuqin; Zhao, Gang; Zhao, Jingkun; Liang, Xian-Ting; Wu, Yaqian; Jia, Yunpeng; Tian, Hao; Liu, J. M.

doi:10.3847/1538-3881/ab5283

Cited by 14 publications

(26 citation statements)

References 48 publications

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“…At a given age from 4 to 12 Gyr, the maximal difference between R g and R b could reach 5 kpc for the most metal-rich stars, indicating that these stars may have a minimal average migration speed of about 0.5 to 1 kpc/Gyr, if we assume that the stars start to migrate since they are born. This is consistent with Quillen et al (2018) and Chen et al (2019b), who suggest that the stellar migration due to the excitation of the Galactic bar have a speed of 0.5-1 kpc/Gyr, depending on the pitch angle of the bar.…”

Section: Churningsupporting

confidence: 91%

“…This is bending mode (Widrow et al 2012;Williams et al 2013;Widrow et al 2014;Sun et al 2015;Carrillo et al 2018;Chequers et al 2018), and the results are similar to the results shown by Williams et al (2013); Carrillo et al (2018); Wang et al (2019b). At the outer disc R ∼ 13 kpc, It is revealed that the vertical velocities in southern disc stars have larger vertical velocities than the northern disc stars, due to the effect of the warp structure (Skowron et al 2019;Chen et al 2019b). The values for J Z show a strong dependence on Z while they are only marginally dependent on R. This is determined by the nature of J Z .…”

Section: Vertical Velocity V Z and Action J Zsupporting

confidence: 76%

Section: Churningmentioning

confidence: 96%

“…Furthermore, the effectiveness of this method has been verified by Chen et al (2019b) via applying to the LAMOST stars. Similar to Chen et al (2019b), here we adopt the Minchev et al (2018) method to estimate the birth radii of our RGB stars. Note that the thick disc stars are widely suggested to exhibit an insignificant radial metallicity gradient, which is explained as an evidence that the disc stars are born from radially well-mixed gas (e.g.…”

Section: Churningmentioning

confidence: 96%

“…These stars are likely a consequence of the radial migration due to the churning process (e.g. Nordström et al 2004;Boeche et al 2013;Kordopatis et al 2013;Xiang et al 2015b;Anders et al 2017;Chen et al 2019b;Wang et al 2019a).…”

mentioning

confidence: 99%

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Age-metallicity dependent stellar kinematics of the Milky Way disc from LAMOST and Gaia

Wu,

Xiang,

Chen

et al. 2020

Preprint

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We investigate the stellar kinematics of the Galactic disc in 7 < R < 13 kpc using a sample of 118 945 red giant branch (RGB) stars from LAMOST and Gaia. We characterize the median, dispersion and skewness of the distributions of the 3D stellar velocities, actions and orbital parameters across the age-metallicity and the disc R -Z plane. Our results reveal abundant but clear stellar kinematic patterns and structures in the age -metallicity and the disc R -Z plane. The most prominent feature is the strong variations of the velocity, action, and orbital parameter distributions from the young, metal-rich thin disc to the old, metal-poor thick disc, a number of smaller-scale structures -such as velocity streams, north-south asymmetries, and kinematic features of spiral arms -are clearly revealed. Particularly, the skewness of V φ and J φ reveals a new substructure at R 12 kpc and Z 0 kpc, possibly related to dynamical effects of spiral arms in the outer disc. We further study the stellar migration through analysing the stellar orbital parameters and stellar birth radii. The results suggest that the thick disc stars near the solar radii and beyond are mostly migrated from the inner disc of R ∼ 4 − 6 kpc due to their highly eccentrical orbits. Stellar migration due to dynamical processes with angular momentum transfer (churning) are prominent for both the old, metal-rich stars (outward migrators) and the young metal-poor stars (inward migrators). The spatial distribution in the R -Z plane for the inward migrators born at a Galactocentric radius of >12 kpc show clear age stratifications, possibly an evidence that these inward migrators are consequences of splashes triggered by merger events of satellite galaxies that have been lasted in the past few giga years.

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Section: Churningsupporting

confidence: 91%

Section: Vertical Velocity V Z and Action J Zsupporting

confidence: 76%

Section: Churningmentioning

confidence: 96%

Section: Churningmentioning

confidence: 96%

mentioning

confidence: 99%

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Age-metallicity dependent stellar kinematics of the Milky Way disc from LAMOST and Gaia

Wu,

Xiang,

Chen

et al. 2020

Preprint

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Gas and dust from metal-rich AGB stars

Ventura

Dell’Agli

Lugaro

et al. 2020

A&A

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Context. Stars evolving through the asymptotic giant branch (AGB) phase provide significant feedback to their host system, which is both gas enriched in nuclear-burning products, and dust formed in their winds, which they eject into the interstellar medium. Therefore, AGB stars are an essential ingredient for the chemical evolution of the Milky Way and other galaxies. Aims. We study AGB models with super-solar metallicities to complete our vast database, so far extending from metal-poor to solar-chemical compositions. We provide chemical yields for masses in the range 1−8 M⊙ and metallicities Z = 0.03 and Z = 0.04. We also study dust production in this metallicity domain. Methods. We calculated the evolutionary sequences from the pre-main sequence through the whole AGB phase. We followed the variation of the surface chemical composition to calculate the chemical yields of the various species and model dust formation in the winds to determine the dust production rate and the total dust mass produced by each star during the AGB phase. Results. The physical and chemical evolution of the star is sensitive to the initial mass: M > 3 M⊙ stars experience hot bottom burning, whereas the surface chemistry of the lower mass counterparts is altered only by third dredge-up. The carbon-star phase is reached by 2.5−3.5 M⊙ stars of metallicity Z = 0.03, whereas all the Z = 0.04 stars (except the 2.5 M⊙) remain O-rich for the whole AGB phase. Most of the dust produced by metal-rich AGBs is in the form of silicate particles. The total mass of dust produced increases with the mass of the star, reaching ∼0.012 M⊙ for 8 M⊙ stars.

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Understanding the evolution and dust formation of carbon stars in the Large Magellanic Cloud via the JWST

Marini

Dell’Agli

Groenewegen

et al. 2021

A&A

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Context. Carbon stars have been, and still are, extensively studied. Given their complex internal structure and their peculiar chemical composition, they are living laboratories in which we can test stellar structure and evolution theories of evolved stars. Furthermore, they are the most relevant dust manufacturers, thus playing a crucial role in the evolution of galaxies. Aims. We aim to study the dust mineralogy of the circumstellar envelope of carbon stars in the Large Magellanic Cloud (LMC) to achieve a better understanding of the dust formation process in the outflow of these objects. We intend to investigate the expected distribution of carbon stars in the observational planes built with the filters of the Mid-Infrared Instrument (MIRI) mounted onboard the James Webb Space Telescope (JWST) to select the best planes allowing an exhaustive characterisation of the stars. Methods. We compared the synthetic spectral energy distributions, obtained by modelling asymptotic giant branch stars and the dust formation process in the wind, with the spectra of carbon stars in the LMC, taken with the Infrared Spectrograph onboard the Spitzer Space Telescope. From the detailed comparison between synthetic modelling and observation we characterise the individual sources and derive the detailed mineralogy of the dust in the circumstellar envelope. Results. The sample of stars considered here is composed of stars of diverse mass, formation epoch, degree of obscuration, and metallicity. We find that precipitation of MgS on SiC seeds is common to all non-metal-poor carbon stars. Solid carbon is the dominant dust component, with percentages above 80% in all cases; a percentage between 10% and 20% of carbon dust is under the form of graphite, the remaining being amorphous carbon. Regarding the observational planes based on the MIRI filters, the colour-magnitude ([F770W]–[F1800W], [F1800W]) plane allows the best understanding of the degree of obscuration of the stars, while the ([F1800W]–[F2550W], [F1800W]) diagram allows better discrimination among stars of different metallicities.

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Super Metal-rich Stars in the LAMOST Survey: A Test on Radial Migration

Cited by 14 publications

References 48 publications

Age-metallicity dependent stellar kinematics of the Milky Way disc from LAMOST and Gaia

Age-metallicity dependent stellar kinematics of the Milky Way disc from LAMOST and Gaia

Gas and dust from metal-rich AGB stars

Understanding the evolution and dust formation of carbon stars in the Large Magellanic Cloud via the JWST

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