scholarly journals Abundances of neutron-capture elements in thin- and thick-disc stars in the solar neighbourhood

2021 ◽  
Author(s):  
G. Tautvaisiené ◽  
C. Viscasillas Vázquez ◽  
S. Mikolaitis ◽  
E. Stonkute ◽  
R. Minkeviciute ◽  
...  
Keyword(s):  
Neutron Capture ◽  
Solar Neighbourhood ◽  
Thick Disc

scholarly journals Gaia DR1 completeness within 250 pc & star formation history of the Solar neighbourhood

2017 ◽  
Vol 12 (S330) ◽  
pp. 148-151 ◽  
Author(s):  
Edouard J. Bernard
Keyword(s):  
Star Formation ◽  
Star Formation History ◽  
Solar Neighbourhood ◽  
The Sun ◽  
Thick Disc ◽  
Formation History ◽  
Magnitude Diagram ◽  
History Of

AbstractWe took advantage of the Gaia DR1 to combine TGAS parallaxes with Tycho-2 and APASS photometry to calculate the star formation history (SFH) of the solar neighbourhood within 250 pc using the colour-magnitude diagram fitting technique. We present the determination of the completeness within this volume, and compare the resulting SFH with that calculated from the Hipparcos catalogue within 80 pc of the Sun. We also show how this technique will be applied out to ~5 kpc thanks to the next Gaia data releases, which will allow us to quantify the SFH of the thin disc, thick disc and halo in situ, rather than extrapolating based on the stars from these components that are today in the solar neighbourhood.

scholarly journals Co-formation of the thin and thick discs revealed by APOGEE-DR16 and Gaia-DR2

2020 ◽  
Author(s):  
Leandro Beraldo e Silva ◽  
Victor P Debattista ◽  
David Nidever ◽  
João A S Amarante ◽  
Bethany Garver
Keyword(s):  
Solar Neighbourhood ◽  
Full Sample ◽  
Thick Disc ◽  
Thin Disc ◽  
Vertical Scale ◽  
Stellar Halo ◽  
Sph Simulation ◽  
Gaia Dr2 ◽  
Cross Match ◽  
Age Estimates

Abstract Since thin disc stars are younger than thick disc stars on average, the thin disc is predicted by some models to start forming after the thick disc had formed, around 10 Gyr ago. Accordingly, no significant old thin disc population should exist. Using 6-D coordinates from Gaia-DR2 and age estimates from Sanders & Das (2018), we select ∼24000 old stars (${\tau > 10{\, \rm{Gyr}}}$, with uncertainties $\lesssim 15\%$) within $2{\, \rm{kpc}}$ from the Sun (full sample). A cross-match with APOGEE-DR16 (∼1000 stars) reveals comparable fractions of old chemically defined thin/thick disc stars. We show that the full sample pericenter radius (rper) distribution has three peaks, one associated with the stellar halo and the other two having contributions from the thin/thick discs. Using a high-resolution N-body+SPH simulation, we demonstrate that one peak, at ${r_\rm{per}}\approx 7.1{\, \rm{kpc}}$, is produced by stars from both discs which were born in the inner Galaxy and migrated to the Solar Neighbourhood. In the Solar Neighbourhood, ∼1/2 (∼1/3) of the old thin (thick) disc stars are classified as migrators. Our results suggest that thin/thick discs are affected differently by radial migration inasmuch as they have different eccentricity distributions, regardless of vertical scale heights. We interpret the existence of a significant old thin disc population as evidence for an early co-formation of thin/thick discs, arguing that clump instabilities in the early disc offer a compelling explanation for the observed trends.

scholarly journals The disc origin of the Milky Way bulge

2018 ◽  
Vol 616 ◽  
pp. A180 ◽  
Author(s):  
F. Fragkoudi ◽  
P. Di Matteo ◽  
M. Haywood ◽  
M. Schultheis ◽  
S. Khoperskov ◽  
...  
Keyword(s):  
Distribution Function ◽  
Milky Way ◽  
Chemical Properties ◽  
Stellar Populations ◽  
Solar Neighbourhood ◽  
Stellar Disc ◽  
Thick Disc ◽  
The Mean ◽  
Metallicity Distribution ◽  
Do So

There is a long-standing debate over the origin of the metal-poor stellar populations of the Milky Way (MW) bulge, with the two leading scenarios being that these populations are either (i) part of a classical metal-poor spheroid or (ii) the same population as the chemically defined thick disc seen at the solar neighbourhood. Here we test whether the latter scenario can reproduce the observed chemical properties of the MW bulge. To do so we compare an N-body simulation of a composite (thin+thick) stellar disc – which evolves secularly to form a bar and a boxy/peanut (b/p) bulge – to data from APOGEE DR13. This model, in which the thick disc is massive and centrally concentrated, can reproduce the morphology of the metal-rich and metal-poor stellar populations in the bulge, as well as the mean metallicity and [α/Fe] maps as obtained from the APOGEE data. It also reproduces the trends, in both longitude and latitude, of the bulge metallicity distribution function (MDF). Additionally, we show that the model predicts small but measurable azimuthal metallicity variations in the inner disc due to the differential mapping of the thin and thick disc in the bar. We therefore see that the chemo-morphological relations of stellar populations in the MW bulge are naturally reproduced by mapping the thin and thick discs of the inner MW into a b/p.

scholarly journals Modelling the chemical evolution of Zr, La, Ce, and Eu in the Galactic discs and bulge

2020 ◽  
Vol 492 (2) ◽  
pp. 2828-2834 ◽  
Author(s):  
V Grisoni ◽  
G Cescutti ◽  
F Matteucci ◽  
R Forsberg ◽  
H Jönsson ◽  
...  
Keyword(s):  
Star Formation ◽  
Chemical Evolution ◽  
Neutron Capture ◽  
Distribution Functions ◽  
Point Of View ◽  
Thick Disc ◽  
Thin Disc ◽  
Abundance Patterns ◽  
History Of ◽  
Star Formation Histories

ABSTRACT We study the chemical evolution of Zr, La, Ce, and Eu in the Milky Way discs and bulge by means of chemical evolution models compared with spectroscopic data. We consider detailed chemical evolution models for the Galactic thick disc, thin disc, and bulge, which have been already tested to reproduce the observed [α/Fe] versus [Fe/H] diagrams and metallicity distribution functions for the three different components, and we apply them to follow the evolution of neutron capture elements. In the [Eu/Fe] versus [Fe/H] diagram, we observe and predict three distinct sequences corresponding to the thick disc, thin disc, and bulge, similar to what happens for the α-elements. We can nicely reproduce the three sequences by assuming different time-scales of formation and star formation efficiencies for the three different components, with the thin disc forming on a longer time-scale of formation with respect to the thick disc and bulge. On the other hand, in the [X/Fe] versus [Fe/H] diagrams for Zr, La, and Ce, the three populations are mixed and also from the model point of view there is an overlapping between the predictions for the different Galactic components, but the observed behaviour can be also reproduced by assuming different star formation histories in the three components. In conclusions, it is straightforward to see how different star formation histories can lead to different abundance patterns and also looking at the abundance patterns of neutron capture elements can help in constraining the history of formation and evolution of the major Galactic components.

scholarly journals A spectroscopic survey of thick disc stars outside the solar neighbourhood

2011 ◽  
Vol 535 ◽  
pp. A107 ◽  
Author(s):  
G. Kordopatis ◽  
A. Recio-Blanco ◽  
P. de Laverny ◽  
G. Gilmore ◽  
V. Hill ◽  
...  
Keyword(s):  
Solar Neighbourhood ◽  
Thick Disc

A spectroscopic survey of the Thick Disc outside the Solar neighbourhood: A comparison with the Besançon model

2010 ◽  
Vol 45 ◽  
pp. 405-408
Author(s):  
G. Kordopatis ◽  
A. Recio-Blanco ◽  
P. de Laverny ◽  
G. Gilmore ◽  
V. Hill ◽  
...  
Keyword(s):  
Solar Neighbourhood ◽  
Thick Disc

Observing the galactic magnetic field

1967 ◽  
Vol 31 ◽  
pp. 375-380
Author(s):  
H. C. van de Hulst
Keyword(s):  
Magnetic Field ◽  
Fair Agreement ◽  
Solar Neighbourhood ◽  
Galactic Magnetic Field ◽  
The Magnetic Field

Various methods of observing the galactic magnetic field are reviewed, and their results summarized. There is fair agreement about the direction of the magnetic field in the solar neighbourhood:l= 50° to 80°; the strength of the field in the disk is of the order of 10-5gauss.

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