Analysis of the disc components of our galaxy via kinematic and spectroscopic procedures

Medientyp: E-Artikel
Titel: Analysis of the disc components of our galaxy via kinematic and spectroscopic procedures
Beteiligte: Karaali, S.; Bilir, S.; Gökçe, E. Yaz; Plevne, O.
Erschienen: Cambridge University Press (CUP), 2019
Erschienen in: Publications of the Astronomical Society of Australia
Sprache: Englisch
DOI: 10.1017/pasa.2019.39
ISSN: 1323-3580; 1448-6083
Schlagwörter: Space and Planetary Science ; Astronomy and Astrophysics
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Beschreibung: <jats:title>Abstract</jats:title> <jats:p>We used the spectroscopic and astrometric data provided from the GALactic Archaeology with HERMES (GALAH) Data Release (DR2) and <jats:italic>Gaia</jats:italic> DR2, respectively, for a large sample of stars to investigate the behaviour of the [<jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" xlink:type="simple" xlink:href="S1323358019000390_inline1" /> <jats:tex-math> $\alpha$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>/Fe] abundances via two procedures, that is, kinematically and spectroscopically. With the kinematical procedure, we investigated the distribution of the [<jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" xlink:type="simple" xlink:href="S1323358019000390_inline2" /> <jats:tex-math> $\alpha$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>/Fe] abundances into the high-/low-probability thin disc, and high-/low-probability thick-disc populations in terms of total space velocity, [Fe/H] abundance, and age. The high-probability thin-disc stars dominate in all sub-intervals of [<jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" xlink:type="simple" xlink:href="S1323358019000390_inline3" /> <jats:tex-math> $\alpha$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>/Fe], including the rich ones: [<jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" xlink:type="simple" xlink:href="S1323358019000390_inline4" /> <jats:tex-math> $\alpha$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>/Fe]<jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" xlink:type="simple" xlink:href="S1323358019000390_inline5" /> <jats:tex-math> $\,>\,0.3$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> dex, where the high-probability thick-disc stars are expected to dominate. This result can be explained by the limiting apparent magnitude of the GALAH DR2 (<jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" xlink:type="simple" xlink:href="S1323358019000390_inline6" /> <jats:tex-math> $V \lt 14$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> mag) and intermediate galactic latitude of the star sample. Stars in the four populations share equivalent [<jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" xlink:type="simple" xlink:href="S1323358019000390_inline7" /> <jats:tex-math> $\alpha$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>/Fe] and [Fe/H] abundances, total space velocities, and ages. Hence, none of these parameters can be used alone for separation of a sample of stars into different populations. High-probability thin-disc stars with abundance <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" xlink:type="simple" xlink:href="S1323358019000390_inline8" /> <jats:tex-math> $-1.3 \lt {\rm[Fe/H]}\leq -0.5$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> dex and age <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" xlink:type="simple" xlink:href="S1323358019000390_inline9" /> <jats:tex-math> $9 \lt \tau\leq13$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> Gyr are assumed to have different birth places relative to the metal-rich and younger ones. With the spectroscopic procedure, we separated the sample stars into <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" xlink:type="simple" xlink:href="S1323358019000390_inline10" /> <jats:tex-math> $\alpha$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>-rich and <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" xlink:type="simple" xlink:href="S1323358019000390_inline11" /> <jats:tex-math> $\alpha$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>-poor categories by means of their ages as well as their [<jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" xlink:type="simple" xlink:href="S1323358019000390_inline12" /> <jats:tex-math> $\alpha$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>/Fe] and [Fe/H] abundances. Stars older than 8 Gyr are richer in [<jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" xlink:type="simple" xlink:href="S1323358019000390_inline13" /> <jats:tex-math> $\alpha$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>/Fe] than the younger ones. We could estimate the abundance [<jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" xlink:type="simple" xlink:href="S1323358019000390_inline14" /> <jats:tex-math> $\alpha$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>/Fe] = 0.14 dex as the boundary separating the <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" xlink:type="simple" xlink:href="S1323358019000390_inline15" /> <jats:tex-math> $\alpha$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>-rich and <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" xlink:type="simple" xlink:href="S1323358019000390_inline16" /> <jats:tex-math> $\alpha$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>-poor sub-samples in the [<jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" xlink:type="simple" xlink:href="S1323358019000390_inline17" /> <jats:tex-math> $\alpha$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>/Fe]<jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" xlink:type="simple" xlink:href="S1323358019000390_inline18" /> <jats:tex-math> $\,\times\,$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>[Fe/H] plane.</jats:p>
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