scholarly journals Binary Fractions of G and K Dwarf Stars Based on Gaia EDR3 and LAMOST DR5: Impacts of the Chemical Abundances

2021 ◽  
Vol 922 (2) ◽  
pp. 211
Author(s):  
Zexi Niu ◽  
Haibo Yuan ◽  
Song Wang ◽  
Jifeng Liu
Keyword(s):  
Thin Disk ◽  
Thick Disk ◽  
Chemical Abundances ◽  
Dwarf Stars ◽  
Halo Stars ◽  
Binary Formation ◽  
Data Release ◽  
Inclination Angles ◽  
Thin And Thick Disks ◽  
Single Epoch

Abstract Based on the large volume Gaia Early Data Release 3 and LAMOST Data Release 5 data, we estimate the bias-corrected binary fractions of the field late G and early K dwarfs. A stellar locus outlier method is used in this work, which works well for binaries of various periods and inclination angles with single-epoch data. With a well-selected, distance-limited sample of about 90,000 GK dwarfs covering wide stellar chemical abundances, it enables us to explore the binary fraction variations with different stellar populations. The average binary fraction is 0.42 ± 0.01 for the whole sample. Thin-disk stars are found to have a binary fraction of 0.39 ± 0.02, thick-disk stars have a higher one of 0.49 ± 0.02, while inner halo stars possibly have the highest binary fraction. For both the thin- and thick-disk stars, the binary fractions decrease toward higher [Fe/H], [α/H], and [M/H] abundances. However, the suppressing impacts of [Fe/H], [α/H], and [M/H] are more significant for the thin-disk stars than those for the thick-disk stars. For a given [Fe/H], a positive correlation between [α/Fe] and the binary fraction is found for the thin-disk stars. However, this tendency disappears for the thick-disk stars. We suspect that it is likely related to the different formation histories of the thin and thick disks. Our results provide new clues for theoretical works on binary formation.

scholarly journals The chemical fingerprints of the thin and the thick disk

2008 ◽  
Vol 4 (S254) ◽  
pp. 197-202
Author(s):  
Sofia Feltzing ◽  
Sally Oey ◽  
Thomas Bensby
Keyword(s):  
Past History ◽  
Thick Disk ◽  
Chemical Abundance ◽  
Dwarf Stars ◽  
Abundance Patterns ◽  
The Galaxy ◽  
Thin And Thick Disks ◽  
Thick Disks ◽  
Definition Of ◽  
Galactic Stellar Populations

AbstractThe past history and origin of the different Galactic stellar populations are manifested in their different chemical abundance patterns. We obtained new elemental abundances for 553 F and G dwarf stars, to more accurately quantify these patterns for the thin and thick disks. However, the exact definition of disk membership is not straightforward. Stars that have a high likelihood of belonging to the thin disk show different abundance patterns from those for the thick disk. In contrast, we show that stars for the Hercules Stream do not show unique abundance patterns, but rather follow those of the thin and thick disks. This strongly suggests that the Hercules Stream is a feature induced by internal dynamics within the Galaxy rather than the remnant of an accreted satellite.

scholarly journals A New Sample of Thick Disk and Halo Stars

1995 ◽  
Vol 164 ◽  
pp. 386-386
Author(s):  
C. Soubiran ◽  
M.N. Perrin ◽  
R. Cayrel ◽  
E. Chereul
Keyword(s):  
Stellar Population ◽  
Thin Disk ◽  
Thick Disk ◽  
The Other ◽  
Chemical Characteristics ◽  
Fundamental Parameters ◽  
Halo Stars ◽  
Synthetic Spectra ◽  
The Galaxy ◽  
Comparison Stars

The aim of our stellar population study is to investigate the kinematical and chemical characteristics of the thin disk, thick disk and halo of the Galaxy. We have selected 51 stars in 2 astrometric and photometric surveys at l = 42°, b = +79° (Soubiran 1992) and l = 167°, b = +47° (Ojha et al. 1994), on the basis of the Reduced Proper Motion Diagram. They were observed with the 193cm telescope at Observatoire de Haute-Provence, with the CARELEC spectrograph (dispersion of 66Å/mm, FWHM of 3.0Å, range λλ4600 – 5500Å), together with 43 comparison stars with known fundamental parameters. The derivation of Teff, logg and [Fe/H] was done differentially using a grid of synthetic spectra and the comparison stars, as described in Cayrel et al. (1991). Twenty of the target stars were found to be more deficient than −0.5. In the (V, [Fe/H]) distribution, the halo stars are clearly separated from the other stars with a mean of (V, [Fe/H]) ≃ (−210km/s, – 1.4dex). Because of the small size of the sample, it was not possible to discriminate the thick disk from the thin disk. We have taken 200 more spectra, and with these new observations, we hope to be able to deconvolve the 3 populations in the (U, V, W, [Fe/H]) space as we did previously with the (U, V) velocity (Soubiran 1993).

Abundance ratios & ages of stellar populations in HARPS-GTO sample

2017 ◽  
Vol 12 (S330) ◽  
pp. 156-159 ◽  
Author(s):  
E. Delgado Mena ◽  
M. Tsantaki ◽  
V. Zh. Adibekyan ◽  
S. G. Sousa ◽  
N. C. Santos ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Thin Disk ◽  
Thick Disk ◽  
Heavy Elements ◽  
Galactic Chemical Evolution ◽  
Chemical Abundances ◽  
Homogeneous Sample ◽  
Different Populations ◽  
Search Program ◽  
Cu And Zn

AbstractIn this work we present chemical abundances of heavy elements (Z>28) for a homogeneous sample of 1059 stars from HARPS planet search program. We also derive ages using parallaxes from Hipparcos and Gaia DR1 to compare the results. We study the [X/Fe] ratios for different populations and compare them with models of Galactic chemical evolution. We find that thick disk stars are chemically disjunt for Zn adn Eu. Moreover, the high-alpha metal-rich population presents an interesting behaviour, with clear overabundances of Cu and Zn and lower abundances of Y and Ba with respect to thin disk stars. Several abundance ratios present a significant correlation with age for chemically separated thin disk stars (regardless of their metallicity) but thick disk stars do not present that behaviour. Moreover, at supersolar metallicities the trends with age tend to be weaker for several elements.

scholarly journals The vertical metallicity gradients of mono-age stellar populations in the Milky Way thin disk

2017 ◽  
Vol 13 (S334) ◽  
pp. 281-282
Author(s):  
Ioana Ciucă ◽  
Daisuke Kawata ◽  
Jane Lin ◽  
Luca Casagrande ◽  
George Seabroke ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Milky Way ◽  
Stellar Populations ◽  
Thin Disk ◽  
Dwarf Stars ◽  
Star Forming ◽  
Data Release ◽  
The Cross

AbstractWe investigate the vertical metallicity gradients of five mono-age stellar populations between 0 and 11 Gyr for a sample of 18 435 dwarf stars selected from the cross-matched Tycho-Gaia Astrometric Solution (TGAS) and RAdial Velocity Experiment (RAVE) Data Release 5. We find a correlation between the vertical metallicity gradients and age, with no vertical metallicity gradient in the youngest population and an increasingly steeper negative vertical metallicity gradient for the older stellar populations. We also find that the intrinsic dispersion in metallicity increases steadily with age. Our results are consistent with a scenario that thin disk stars formed from a flaring thin star-forming disk.

scholarly journals The radial extent of the Galactic thick disk

2016 ◽  
Vol 11 (S321) ◽  
pp. 3-5
Author(s):  
Thomas Bensby
Keyword(s):  
Milky Way ◽  
Galactic Disk ◽  
Thin Disk ◽  
Thick Disk ◽  
Stellar Disk ◽  
Chemical Signatures ◽  
Radial Extent ◽  
Thin And Thick Disks ◽  
Thick Disks ◽  
Scale Length

AbstractBased on observational data from the fourth internal data release of the Gaia-ESO Survey we probe the abundance structure in the Milky Way stellar disk as a function of galactocentric radius and height above the plane. We find that the inner and outer Galactic disks have different chemical signatures. The stars in the inner Galactic disk show abundance signatures of both the thin and thick disks, while the stars in the outer Galactic disk resemble in majority the abundances seen in the thin disk. Assuming that the Galactic thick disk can be associated with the α-enriched population, this can be interpreted as that the thick disk density drops drastically beyond a galactocentric radius of about 10 kpc. This is in agreement with recent findings that the thick disk has a short scale-length, shorter than that of the the thin disk.

scholarly journals The Galactic Disk-Halo Transition – Evidence from Stellar Abundances

2008 ◽  
Vol 4 (S254) ◽  
pp. 103-108 ◽  
Author(s):  
Poul Erik Nissen ◽  
William J. Schuster
Keyword(s):  
Milky Way ◽  
Galactic Disk ◽  
Thin Disk ◽  
Thick Disk ◽  
Chemical Abundance ◽  
Elemental Abundances ◽  
Halo Stars ◽  
New Information ◽  
First Results ◽  
Satellite Galaxies

AbstractNew information on the relations between the Galactic disks, the halo, and satellite galaxies is being obtained from elemental abundances of stars having metallicities in the range −1.5 < [Fe/H] < −0.5. The first results for a sample of 26 halo stars and 13 thick-disk stars observed with the ESO VLT/UVES spectrograph are presented. The halo stars fall in two distinct groups: one group (9 stars) has [α/Fe] = 0.30 ± 0.03 like the thick-disk stars. The other group (17 stars) shows a clearly deviating trend ranging from [α/Fe] = 0.20 at [Fe/H] = −1.3 to [α/Fe] = 0.08 at [Fe/H] = −0.8. The kinematics of the stars are discussed and the abundance ratios Na/Fe, Ni/Fe, Cu/Fe and Ba/Y are applied to see if the “low-alpha” stars are connected to the thin disk or to Milky Way satellite galaxies. Furthermore, we compare our data with simulations of chemical abundance distributions in hierarchically formed stellar halos in a ΛCDM Universe.

scholarly journals Abundances of α-Process Elements in Thin-Disk, Thick-Disk, and Halo Stars of the Galaxy: Non-LTE Analysis

2019 ◽  
Vol 63 (9) ◽  
pp. 726-738 ◽  
Author(s):  
L. I. Mashonkina ◽  
M. D. Neretina ◽  
T. M. Sitnova ◽  
Yu. V. Pakhomov
Keyword(s):  
Thin Disk ◽  
Thick Disk ◽  
Halo Stars ◽  
The Galaxy ◽  
Process Elements

scholarly journals Abundance to age ratios in the HARPS-GTO sample with Gaia DR2

2019 ◽  
Vol 624 ◽  
pp. A78 ◽  
Author(s):  
E. Delgado Mena ◽  
A. Moya ◽  
V. Adibekyan ◽  
M. Tsantaki ◽  
J. I. González Hernández ◽  
...  
Keyword(s):  
Temporal Evolution ◽  
Thin Disk ◽  
Thick Disk ◽  
Clear Correlation ◽  
Chemical Abundances ◽  
Empirical Relations ◽  
Stellar Ages ◽  
Small Uncertainty ◽  
The Galaxy ◽  
Process Elements

Aims. The purpose of this work is to evaluate how several elements produced by different nucleosynthesis processes behave with stellar age and provide empirical relations to derive stellar ages from chemical abundances. Methods. We derived different sets of ages using Padova and Yonsei–Yale isochrones and HIPPARCOS and Gaia parallaxes for a sample of more than 1000 FGK dwarf stars for which he have high-resolution (R ~ 115 000) and high-quality spectra from the HARPS-GTO program. We analyzed the temporal evolution of different abundance ratios to find the best chemical clocks. We applied multivariable linear regressions to our sample of stars with a small uncertainty on age to obtain empirical relations of age as a function of stellar parameters and different chemical clocks. Results. We find that [α/Fe] ratio (average of Mg, Si, and Ti), [O/Fe] and [Zn/Fe] are good age proxies with a lower dispersion than the age-metallicity dispersion. Several abundance ratios present a significant correlation with age for chemically separated thin disk stars (i.e., low-α) but in the case of the chemically defined thick disk stars (i.e., high-α) only the elements Mg, Si, Ca, and Ti II show a clear correlation with age. We find that the thick disk stars are more enriched in light-s elements than thin disk stars of similar age. The maximum enrichment of s-process elements in the thin disk occurs in the youngest stars which in turn have solar metallicity. The slopes of the [X/Fe]-age relations are quite constant for O, Mg, Si, Ti, Zn, Sr, and Eu regardless of the metallicity. However, this is not the case for Al, Ca, Cu and most of the s-process elements, which display very different trends depending on the metallicity. This demonstrates the limitations of using simple linear relations based on certain abundance ratios to obtain ages for stars of different metallicities. Finally, we show that by using 3D relations with a chemical clock and two stellar parameters (either Teff, [Fe/H] or stellar mass) we can explain up to 89% of age variance in a star. A similar result is obtained when using 2D relations with a chemical clock and one stellar parameter, explaining up to a 87% of the variance. Conclusions. The complete understanding of how the chemical elements were produced and evolved in the Galaxy requires the knowledge of stellar ages and precise chemical abundances. We show how the temporal evolution of some chemical species change with metallicity, with remarkable variations at super-solar metallicities, which will help to better constrain the yields of different nucleosynthesis processes along the history of the Galaxy.

scholarly journals 2MASS Star Counts and Galactic Structure

2001 ◽  
Vol 204 ◽  
pp. 213-213
Author(s):  
D. K. Ojha
Keyword(s):  
Near Infrared ◽  
Local Density ◽  
Global Analysis ◽  
Thin Disk ◽  
Thick Disk ◽  
Sky Survey ◽  
Radial Structure ◽  
Thin And Thick Disks ◽  
Density Scale ◽  
Scale Length

This paper presents a global analysis of the first 2MASS (Two Micron All Sky Survey) data as observed in seven fields at different Galactic latitudes. These new data lead to strong constraints on the radial structure of the Galactic thin and thick disks. The interpretation of star counts and color distributions of stars in the near-infrared with a synthetic stellar population model provides strong evidence that the Galactic thin disk density scale length, hR, is rather short (2.8±0.3 kpc). The Galactic thick disk population is revisited in the light of new data. We find the thick disk to have a local density of 3.5 ± 2.0% of the thin disk, exponential scale height, hz, of 860±200 pc and exponential scale length, hR, of

scholarly journals Phylogeny of the Milky Way’s inner disk and bulge populations: Implications for gas accretion, (the lack of) inside-out thick disk formation, and quenching

2018 ◽  
Vol 618 ◽  
pp. A78 ◽  
Author(s):  
Misha Haywood ◽  
Paola Di Matteo ◽  
Matthew Lehnert ◽  
Owain Snaith ◽  
Francesca Fragkoudi ◽  
...  
Keyword(s):  
Star Formation ◽  
Accretion Rate ◽  
Large Fraction ◽  
Formation Rate ◽  
Thin Disk ◽  
Thick Disk ◽  
Star Formation History ◽  
Two Phase ◽  
Disk Formation ◽  
Gas Accretion

We show that the bulge and the disk of the Milky Way (MW) at R ≲ 7 kpc are well described by a unique chemical evolution and a two-phase star formation history (SFH). We argue that the populations within this inner disk, not the entire disk, are the same, and that the outer Lindblad resonance (OLR) of the bar plays a key role in explaining this uniformity. In our model of a two-phase SFH, the metallicity, [α/Fe] and [α/H] distributions, and age-metallicity relation are all compatible with the observations of both the inner disk and bulge. The dip at [Fe/H] ∼ 0 dex seen in the metallicity distributions of the bulge and inner disk reflects the quenching episode in the SFH of the inner MW at age ∼8 Gyr, and the common evolution of the bulge and inner disk stars. Our results for the inner region of the MW, R ≲ 7 kpc, are consistent with a rapid build-up of a large fraction of its total baryonic mass within a few billion years. We show that at z ≤ 1.5, when the MW was starting to quench, transitioning between the end of the α-enhanced thick disk formation to the start of the thin disk, and yet was still gas rich, the gas accretion rate could not have been significant. The [α/Fe] abundance ratio before and after this quenching phase would be different, which is not observed. The decrease in the accretion rate and gas fraction at z ≤ 2 was necessary to stabilize the disk allowing the transition from thick to thin disks, and for beginning the secular phase of the MW’s evolution. This possibly permitted a stellar bar to develop which we hypothesize is responsible for quenching the star formation. The present analysis suggests that MW history, and in particular at the transition from the thick to the thin disk – the epoch of the quenching – must have been driven by a decrease of the star formation efficiency. We argue that the decline in the intensity of gas accretion, the formation of the bar, and the quenching of the star formation rate (SFR) at the same epoch may be causally connected thus explaining their temporal coincidence. Assuming that about 20% of the gas reservoir in which metals are diluted is molecular, we show that our model is well positioned on the Schmidt-Kennicutt relation at all times.

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