Metal Abundances and Kinematics of Bright Metal-poor Giants Selected from the LSE Survey: Implications for the Metal-weak Thick Disk

Beers, Timothy C.; Drilling, J. S.; Rossi, Silvia; Chiba, Masashi; Rhee, Jaehyon; Fuhrmeister, B.; Norris, John E.; Hippel, Ted von

doi:10.1086/341377

Cited by 88 publications

(73 citation statements)

References 39 publications

(67 reference statements)

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“…Metal-poor stars probe the early evolution of the Galaxy and give clues to the origin of its first components. Among the MW components containing a large fraction of metal-poor stars are the thick disk (originally known as Intermediate Pop II stars and later reidentified by Yoshii 1982;Gilmore & Reid 1983) via its metal-poor extension (the metal-weak thick disk, MWTD, Morrison 1993;Chiba & Beers 2000;Beers et al 2002), globular clusters, dwarf MW satellite galaxies, and the halo, possibly separating into inner-and outer-halo components (Hartwick 1987;Sommer-Larsen & Zhen 1990;Allen et al 1991;Kinman et al 1994;Norris 1994;Carollo et al 2007Carollo et al , 2010Beers et al 2012), but containing sub-populations of globular clusters (Zinn 1993) and fields stars accreted from hierarchical formation, which undoubtedly played a key role in the formation of the halo. A long standing problem is whether and how these different populations may be discriminated from one another by their spatial, kinematical, and chemical distributions.…”

Section: Introductionmentioning

confidence: 99%

Disentangling the Galactic Halo with APOGEE. I. Chemical and Kinematical Investigation of Distinct Metal-poor Populations

Hayes

Majewski

Shetrone

et al. 2018

ApJ

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158

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We find two chemically distinct populations separated relatively cleanly in the [Fe/H]-[Mg/Fe] plane, but also distinguished in other chemical planes, among metal-poor stars (primarily with metallicities < -[ ] Fe H 0.9) observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE) and analyzed for Data Release 13 (DR13) of the Sloan Digital Sky Survey. These two stellar populations show the most significant differences in their [X/Fe] ratios for the α-elements, C+N, Al, and Ni. In addition to these populations having differing chemistry, the low metallicity high-Mg population (which we denote "the HMg population") exhibits a significant net Galactic rotation, whereas the low-Mg population (or "the LMg population") has halo-like kinematics with little to no net rotation. Based on its properties, the origin of the LMg population is likely an accreted population of stars. The HMg population shows chemistry (and to an extent kinematics) similar to the thick disk, and is likely associated with in situ formation. The distinction between the LMg and HMg populations mimics the differences between the populations of low-and high-α halo stars found in previous studies, suggesting that these are samples of the same two populations.

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Section: Introductionmentioning

confidence: 99%

Disentangling the Galactic Halo with APOGEE. I. Chemical and Kinematical Investigation of Distinct Metal-poor Populations

Hayes

Majewski

Shetrone

et al. 2018

ApJ

Self Cite

158

122

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“…Such stars are often selected for kinematical study by their metallicity ([Fe/H] in the range -0.5 and -1 dex) or for chemical study by their kinematics (rotational lag behind the LSR taken to be 20-60 km s −1 and larger). However, there is strong evidence for both the extremely metal-week tail to [Fe/H] below -1.6 dex (Beers et al 2002) and the high-metallicity tail extending to super-solar values (Bensby et al 2003) in the distribution of the thick-disk field stars, which indicates that [Fe/H] is less discriminant than velocities to separate this population.…”

Section: Introductionmentioning

confidence: 99%

Stellar Populations of the Galactic Disk: Metallicity Distribution and Kinematics

et al. 2003

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Abstract.Metallicities and distances have been determined from Vilnius photometry for an in situ sample of nearly 650 stars in eight proper-motion fields at high Galactic latitudes. For half of these stars, radial velocities have been measured with the CORAVEL spectrometer, which allowed us to derive spatial velocities and Galactic orbits. In this contribution we present a status report on our results for the stellar content of the Galactic disk, with emphasis given to specific aspects of distinguishing the thick-disk stars from the old thin-disk population.

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“…We could not see a significant peak at around the period of the RV variation. the infrared dust emission maps of Schlegel et al (1998) and was calibrated according to Beers et al (2002). Assuming the extinction to reddening ratio to be 3.1, the interstellar extinction was found to be at most A V = 0.047.…”

Section: Discussionmentioning

confidence: 99%

A Jupiter-mass planet around the K0 giant HD 208897

Yılmaz

Sato

Bikmaev

et al. 2017

A&A

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For over 10 years, we have carried out a precise radial velocity (RV) survey to find substellar companions around evolved G,K-type stars to extend our knowledge of planet formation and evolution. We performed high precision RV measurements for the giant star HD 208897 using an iodine (I 2 ) absorption cell. The measurements were made at TÜBİTAK National Observatory (TUG; RTT150) and Okayama Astrophysical Observatory (OAO). For the origin of the periodic variation seen in the RV data of the star, we adopted a Keplerian motion caused by an unseen companion. We found that the star hosts a planet with a minimum mass of m 2 sini = 1.40M J , which is relatively low compared to those of known planets orbiting evolved intermediate-mass stars. The planet is in a nearly circular orbit with a period of P = 353 days at about 1 AU distance from the host star. The star is metal rich and located at the early phase of ascent along the red giant branch. The photometric observations of the star at Ankara University Kreiken Observatory (AUKR) and the HIPPARCOS photometry show no sign of variation with periods associated with the RV variation. Neither bisector velocity analysis nor analysis of the Ca II and Hα lines shows any correlation with the RV measurements.

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Metal Abundances and Kinematics of Bright Metal-poor Giants Selected from the LSE Survey: Implications for the Metal-weak Thick Disk

Cited by 88 publications

References 39 publications

Disentangling the Galactic Halo with APOGEE. I. Chemical and Kinematical Investigation of Distinct Metal-poor Populations

Disentangling the Galactic Halo with APOGEE. I. Chemical and Kinematical Investigation of Distinct Metal-poor Populations

Stellar Populations of the Galactic Disk: Metallicity Distribution and Kinematics

A Jupiter-mass planet around the K0 giant HD 208897

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