A new<i>α</i>-enhanced super-solar metallicity population

Adibekyan, V.; Santos, N. C.; Sousa, S. G.; Israelian, G.

doi:10.1051/0004-6361/201118240

Cited by 154 publications

(238 citation statements)

References 43 publications

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“…Here we use this dichotomy in the chemical evolution to separate different stellar populations. Adibekyan et al (2011) showed that the stars of this sample fall into two populations, clearly separated in terms of [α/Fe] up to super-solar metallicities. In turn, high-α stars were also separated into two families with a gap in both [α/Fe] Adibekyan et al (2011) to separate the stellar groups 4 .…”

Section: Dissecting the Galactic Disksmentioning

confidence: 87%

“…It is becoming increasingly clear that a dissection of the Galactic disks based only on stellar abundances is superior to kinematic separation (e.g., Navarro et al 2011;Lee et al 2011;Adibekyan et al 2011;Liu & van de Ven 2012). This is because chemistry is a relatively more stable property of a star than its spatial positions and kinematics.…”

Section: The Sample and Disk Definitionmentioning

confidence: 99%

“…These two populations have different kinematics and chemical properties. Generally, the thick disk is thought to be composed of relatively old stars (e.g., Bensby et al 2003Bensby et al , 2005Fuhrmann 2008;Adibekyan et al 2011), metal-poor, and α-enhanced (e.g., Fuhrmann 1998Fuhrmann , 2008Prochaska et al 2000;Feltzing et al 2003;Reddy et al 2006;Haywood 2008;Lee et al 2011;Adibekyan et al 2012) that move in Galactic orbits with a largescale height and long-scale length (e.g., Robin et al 1996;Buser et al 1999;Jurić et al 2008;Kordopatis et al 2011). However, some of the observed trends may depend on the criteria applied to divide stars into the two disk populations (e.g., Fuhrmann 2008;Schönrich & Binney 2009b;Lee et al 2011).…”

Section: Introductionmentioning

confidence: 99%

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Kinematics and chemical properties of the Galactic stellar populations

Adibekyan

Figueira

Santos

et al. 2013

A&A

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158

202

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Aims. We analyzed chemical and kinematical properties of about 850 FGK solar neighborhood long-lived dwarfs observed with the HARPS high-resolution spectrograph. The stars in the sample have log g ≥ 4 dex, 5000 ≤ T eff ≤ 6500 K, and −1.39 ≤ [Fe/H] ≤ 0.55 dex. The aim of this study is to characterize and explore the kinematics and chemical properties of stellar populations of the Galaxy in order to understand their origins and evolution. Methods. We applied a purely chemical analysis approach based on the [α/Fe] vs. [Fe/H] plot to separate Galactic stellar populations into the thin disk, thick disk, and high-α metal-rich (hαmr). Then, we explored the population's stellar orbital eccentricity distributions, their correlation with metallicity, and rotational velocity gradients with metallicity in the Galactic disks to provide constraints on the various formation models. Results. We identified a gap in the [α/Fe]-[Fe/H] plane for the α-enhanced stars, and by performing a bootstrapped Monte Carlo test we obtained a probability higher than 99.99% that this gap is not due to small-number statistics. Our analysis shows a negative gradient of the rotational velocity of the thin disk stars with [Fe/H] (-17 km s −1 dex −1 ), and a steep positive gradient for both the thick disk and hαmr stars with the same magnitude of about +42 km s −1 dex −1 . For the thin disk stars we observed no correlation between orbital eccentricities and metallicity, but observed a steep negative gradient for the thick disk and hαmr stars with practically the same magnitude (≈-0.18 dex −1 ). The correlations observed for the nearby stars (on average 45 pc) using high-precision data, in general agree well with the results obtained for the SDSS sample of stars located farther from the Galactic plane. Conclusions. Our results suggest that radial migration played an important role in the formation and evolution of the thin disk. For the thick disk stars it is not possible to reach a firm conclusion about their origin. Based on the eccentricity distribution of the thick disk stars only their accretion origin can be ruled out, and the heating and migration scenario could explain the positive steep gradient of V φ with [Fe/H]. When we analyzed the hαmr stellar population we found that they share properties of both the thin and thick disk population. A comparison of the properties of the hαmr stars with those of the subsample of stars from the N-body/SPH simulation using radial migration suggest that they may have originated from the inner Galaxy. Further detailed investigations would help to clarify their exact nature and origin.

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Section: Dissecting the Galactic Disksmentioning

confidence: 87%

Section: The Sample and Disk Definitionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Kinematics and chemical properties of the Galactic stellar populations

Adibekyan

Figueira

Santos

et al. 2013

A&A

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158

202

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“…The similarity in [α/Fe] between the thin and thick disc clusters with ages of 4 to 9 Gyr suggest that age cannot be the key variable, but different proportions of Type II to Type Ia supernovae products in clusters formed at dif- Adibekyan et al 2013;Bensby et al 2014). Although the origin of such objects is still in debate, Adibekyan et al (2011Adibekyan et al ( , 2013 have suggested a possible origin of these α-enhanced metal-rich stars in the inner Galaxy (bulge) followed by a subsequent migration to the solar vicinity.…”

Section: [α/Fe] Vs Cluster's Agementioning

confidence: 99%

The evolution of the Milky Way: new insights from open clusters

Reddy¹,

Lambert²,

Giridhar³

2016

Mon. Not. R. Astron. Soc.

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We have collected high-dispersion echelle spectra of red giant members in the twelve open clusters (OCs) and derived stellar parameters and chemical abundances for 26 species by either line equivalent widths or synthetic spectrum analyses. We confirm the lack of an age−metallicity relation for OCs but argue that such a lack of trend for OCs arise from the limited coverage in metallicity compared to that of field stars which span a wide range in metallicity and age. We confirm that the radial metallicity gradient of OCs is steeper (flatter) for R gc < 12 kpc (>12 kpc). We demonstrate that the sample of clusters constituting a steep radial metallicity gradient of slope −0.052±0.011 dex kpc −1 at R gc < 12 kpc are younger than 1.5 Gyr and located close to the Galactic midplane (| z| < 0.5 kpc) with kinematics typical of the thin disc. Whereas the clusters describing a shallow slope of −0.015±0.007 dex kpc −1 at R gc > 12 kpc are relatively old, thick disc members with a striking spread in age and height above the midplane (0.5 < | z| < 2.5 kpc). Our investigation reveals that the OCs and field stars yield consistent radial metallicity gradients if the comparison is limited to samples drawn from the similar vertical heights. We argue via the computation of Galactic orbits that all the outer disc clusters were actually born inward of 12 kpc but the orbital eccentricity has taken them to present locations very far from their birthplaces.

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“…Adibekyan et al 2011;Recio-Blanco et al 2014) and kinematic approaches (e.g. Bensby et al 2003;Reddy et al 2006).…”

Section: Kinematic Propertiesmentioning

confidence: 99%

CNO behaviour in planet-harbouring stars

Suárez-Andrés

Israelian

Hernández

et al. 2016

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Context. Carbon, nitrogen, and oxygen (CNO) are key elements in stellar formation and evolution, and their abundances should also have a significant impact on planetary formation and evolution. Aims. We present a detailed spectroscopic analysis of 74 solar-type stars, 42 of which are known to harbour planets. We determine the nitrogen abundances of these stars and investigate a possible connection between N and the presence of planetary companions. Methods. We used VLT/UVES to obtain high-resolution near-UV spectra of our targets. Spectral synthesis of the NH band at 3360 Å was performed with the spectral synthesis codes MOOG and FITTING. Results. We identify several spectral windows from which accurate N abundance can be obtained. Nitrogen distributions for stars with and without planets show that planet hosts are nitrogen-rich when compared to single stars. However, given the linear trend between [N/Fe] vs. [Fe/H], this fact can be explained as being due to the metal-rich nature of planet hosts. Conclusions. We conclude that reliable N abundances can be derived for metal-rich solar type stars from the near UV molecular band at 3360 Å. We confirm a linear trend between [N/Fe] and metallicity expected from standard models of Galactic chemical evolution.

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A newα-enhanced super-solar metallicity population

Cited by 154 publications

References 43 publications

Kinematics and chemical properties of the Galactic stellar populations

Kinematics and chemical properties of the Galactic stellar populations

The evolution of the Milky Way: new insights from open clusters

CNO behaviour in planet-harbouring stars

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