scholarly journals Nitrogen evolution in the halo, thick disc, thin disc, and bulge of the Galaxy

2021 ◽  
Vol 508 (1) ◽  
pp. 719-727
Author(s):  
V Grisoni ◽  
F Matteucci ◽  
D Romano
Keyword(s):  
Galactic Halo ◽  
Massive Stars ◽  
Chemical Elements ◽  
Distribution Functions ◽  
Abundance Pattern ◽  
Origin And Evolution ◽  
Thick Disc ◽  
Thin Disc ◽  
Abundance Patterns ◽  
The Galaxy

ABSTRACT We study the evolution of nitrogen (N) in the Galactic halo, thick disc, thin disc, and bulge by comparing detailed chemical evolution models with recent observations. The models used in this work have already been constrained to explain the abundance patterns of α-elements and the metallicity distribution functions of halo, disc, and bulge stars; here, we adopt them to investigate the origin and evolution of N in the different Galactic components. First, we consider different sets of yields and study the importance of the various channels proposed for N production. Secondly, we apply the reference models to study the evolution of both the Galactic discs and bulge. We conclude that: i) primary N produced by rotating massive stars is required to reproduce the plateau in log(N/O) and [N/Fe] ratios at low metallicity, as well as the secondary and primary production from low- and intermediate-mass stars to reproduce the data of the thin disc; ii) the parallel model can provide a good explanation of the evolution of N abundance in the thick and thin discs, and we confirm that the thick disc has evolved much faster than the thin disc, in agreement with the results from the abundance patterns of other chemical elements; and iii) finally, we present new model predictions for N evolution in the Galactic bulge, and we show that the observations in bulge stars can be explained if massive stars rotate fast during the earliest phases of Galactic evolution, in agreement with findings from the abundance pattern of carbon.

scholarly journals Fluorine in the solar neighbourhood: modelling the Galactic thick and thin discs

2020 ◽  
Vol 498 (1) ◽  
pp. 1252-1258 ◽  
Author(s):  
V Grisoni ◽  
D Romano ◽  
E Spitoni ◽  
F Matteucci ◽  
N Ryde ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Chemical Elements ◽  
Distribution Functions ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Origin And Evolution ◽  
Thin Disc ◽  
Halo Stars ◽  
Abundance Patterns ◽  
Giant Branch Stars

ABSTRACT We investigate the evolution of the abundance of fluorine in the Milky Way thick and thin discs by means of detailed chemical evolution models compared with recent observational data. The chemical evolution models adopted here have already been shown to fit the observed abundance patterns of CNO and α-elements as well as the metallicity distribution functions for the Galactic thick and thin disc stars. We apply them here to the study of the origin and evolution of fluorine, which is still a matter of debate. First, we study the importance of the various sites proposed for the production of fluorine. Then, we apply the reference models to follow the evolution of the two different Galactic components. We conclude that rotating massive stars are important producers of F and they can set a plateau in F abundance below [Fe/H] = −0.5 dex, though its existence for [Fe/H]<−1 has yet to be confirmed by extensive observations of halo stars. In order to reproduce the F abundance increase in the discs at late times, instead, a contribution from lower mass stars – single asymptotic giant branch stars and/or novae – is required. The dichotomy between the thick and thin discs is more evident in the [F/O] versus [O/H] plot than in the [F/Fe] versus [Fe/H] one, and we confirm that the thick disc has evolved much faster than the thin disc, in agreement with findings from the abundance patterns of other chemical elements.

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 Know thy star, know thy planet: chemo-kinematically characterizing TESS targets

2019 ◽  
Vol 491 (3) ◽  
pp. 4365-4381 ◽  
Author(s):  
Andreia Carrillo ◽  
Keith Hawkins ◽  
Brendan P Bowler ◽  
William Cochran ◽  
Andrew Vanderburg
Keyword(s):  
Distribution Functions ◽  
Target List ◽  
Thick Disc ◽  
Thin Disc ◽  
Candidate Target ◽  
Stellar Properties ◽  
The Individual ◽  
Host Stars ◽  
Gaia Dr2 ◽  
Kinematic Properties

ABSTRACT The Transiting Exoplanet Survey Satellite (TESS) has already begun to discover what will ultimately be thousands of exoplanets around nearby cool bright stars. These potential host stars must be well understood to accurately characterize exoplanets at the individual and population levels. We present a catalogue of the chemo-kinematic properties of 2218 434 stars in the TESS Candidate Target List using survey data from Gaia DR2, APOGEE, GALAH, RAVE, LAMOST, and photometrically derived stellar properties from SkyMapper. We compute kinematic thin disc, thick disc, and halo membership probabilities for these stars and find that though the majority of TESS targets are in the thin disc, 4 per cent of them reside in the thick disc and <1 per cent of them are in the halo. The TESS Objects of Interest in our sample also display similar contributions from the thin disc, thick disc, and halo with a majority of them being in the thin disc. We also explore metallicity and [α/Fe] distributions for each Galactic component and show that each cross-matched survey exhibits metallicity and [α/Fe] distribution functions that peak from higher to lower metallicity and lower to higher [α/Fe] from the thin disc to the halo. This catalogue will be useful to explore planet occurrence rates, among other things, with respect to kinematics, component membership, metallicity, or [α/Fe].

scholarly journals Supernova Yields for Chemical Evolution Modeling

2013 ◽  
Vol 9 (S298) ◽  
pp. 154-166
Author(s):  
Ken'ichi Nomoto ◽  
Tomoharu Suzuki
Keyword(s):  
Chemical Evolution ◽  
Massive Stars ◽  
Elemental Abundance ◽  
Solar Abundance ◽  
Abundance Pattern ◽  
Chemical Enrichment ◽  
Abundance Patterns ◽  
Yield Table ◽  
Supernova Explosions ◽  
Evolution Modeling

AbstractWe review the recent results of the nucleosynthesis yields of massive stars. We examine how those yields are affected by some hydrodynamical effects during the supernova explosions, namely, explosion energies from those of hypernovae to faint supernovae, mixing and fallback of processed materials, asphericity, etc. Those parameters in the supernova nucleosynthesis models are constrained from observational data of supernovae and metal-poor stars. The elemental abundance patterns observed in extremely metal-poor stars show some peculiarities relative to the solar abundance pattern, which suggests the important contributions of hypernovae and faint supernovae in the early chemical enrichment of galaxies. These constraints on supernova nucleosynthesis are taken into account in the latest yield table for chemical evolution modeling.

scholarly journals New Beryllium results in halo stars from Keck/HIRES spectra

2009 ◽  
Vol 5 (S268) ◽  
pp. 231-236
Author(s):  
Ann Merchant Boesgaard ◽  
Jeffrey A. Rich ◽  
Emily M. Levesque ◽  
Brendan P. Bowler
Keyword(s):  
Galactic Halo ◽  
Massive Stars ◽  
High Energy ◽  
High Signal ◽  
Signal To Noise ◽  
Interstellar Gas ◽  
Halo Stars ◽  
Spallation Reactions ◽  
Blue Straggler ◽  
The Galaxy

AbstractWe have obtained high-resolution, high signal-to-noise Keck spectra to determine Be abundances in over 100 stars in the Galactic halo. The stellar metallicities range from [Fe/H] = −0.50 to −3.50. Using this large sample, we have examined the trends of Be with Fe and Be with O. We find a real dispersion in Be at a given [O/H] that indicates that Be may not be a good cosmochronometer. Our results indicate that the dominant production mechanism for Be changes as the Galaxy ages. In the early eras of the Galaxy, when massive stars become supernovae, Be is produced from the acceleration of energetic CNO atoms which bombard protons in the vicinity of supernovae. Later spallation reactions occur as high energy protons bombard CNO atoms in the interstellar gas. The change occurs near [Fe/H] = −2.2. We have found that Be is deficient in Li-deficient halo stars, which favors the blue straggler analog hypothesis.

scholarly journals Planetary mass–radius relations across the galaxy

2020 ◽  
Vol 639 ◽  
pp. A66 ◽  
Author(s):  
A. Michel ◽  
J. Haldemann ◽  
C. Mordasini ◽  
Y. Alibert
Keyword(s):  
Bulk Composition ◽  
Chemical Species ◽  
Stellar Populations ◽  
Chemical Abundance ◽  
Thick Disc ◽  
Thin Disc ◽  
Planetary Mass ◽  
The Galaxy ◽  
Galactic Stellar Populations ◽  
Internal Structure Models

Context. Planet formation theory suggests that planet bulk compositions are likely to reflect the chemical abundance ratios of their host star’s photosphere. Variations in the abundance of particular chemical species in stellar photospheres between different galactic stellar populations demonstrate that there are differences among the expected solid planet bulk compositions. Aims. We aim to present planetary mass-radius relations of solid planets for kinematically differentiated stellar populations, namely, the thin disc, thick disc, and halo. Methods. Using two separate internal structure models, we generated synthetic planets using bulk composition inputs derived from stellar abundances. We explored two scenarios, specifically iron-silicate planets at 0.1 AU and silicate-iron-water planets at 4 AU. Results. We show that there is a persistent statistical difference in the expected mass-radius relations of solid planets among the different galactic stellar populations. At 0.1 AU for silicate-iron planets, there is a 1.51–2.04% mean planetary radius difference between the thick and thin disc stellar populations, whilst for silicate-iron-water planets past the ice line at 4 AU, we calculate a 2.93–3.26% difference depending on the models. Between the halo and thick disc, we retrieve at 0.1 AU a 0.53–0.69% mean planetary radius difference, and at 4 AU we find a 1.24–1.49% difference depending on the model. Conclusions. Future telescopes (such as PLATO) will be able to precisely characterize solid exoplanets and demonstrate the possible existence of planetary mass-radius relationship variability between galactic stellar populations.

scholarly journals Abundance Patterns Among Very Metal-Poor Stars in the Halo of the Galaxy: A Statistical Approach

2009 ◽  
Vol 5 (S262) ◽  
pp. 412-413
Author(s):  
Vinicius M. Placco ◽  
Silvia Rossi ◽  
Timothy C. Beers ◽  
Sara Lucatello
Keyword(s):  
Neutron Capture ◽  
Statistical Approach ◽  
Chemical Elements ◽  
Comprehensive Analysis ◽  
Elemental Abundances ◽  
Abundance Patterns ◽  
The Galaxy ◽  
R Process ◽  
Early Galaxy ◽  
Natural Groups

AbstractThe main goal of this work is to explore the abundance patterns of the very metal-poor stars ([Fe/H]<−2.0) observed by the HERES (Hamburg ESO R-process Enhanced Star - Christlieb et al. 2004) survey. This type of study allows the analysis of the correlations among chemical elements, and place some constraints on the operation of the neutron-capture (r and s) processes in the early Galaxy. This approach makes use of statistical tools, such as agglomerative nesting, which can identify the formation of natural groups based on relations among elemental abundances (e.g. [C/Fe], [Sr/Fe], [Ba/Fe], and [Eu/Fe]), and can also be used in a series of “large-sample like” studies.This study provides a comprehensive analysis of a sample of 326 metal-poor stars, and introduces two new subclasses (r-0 and s-I) for metal-poor stars with determined abundances of neutron-capture elements, aiming to standardize the nomenclature for those objects and, by reproducing previous results, confirms the validity of the statistical method used.

scholarly journals Constraints on stellar rotation from the evolution of Sr and Ba in the Galactic halo

2021 ◽  
Vol 502 (2) ◽  
pp. 2495-2507
Author(s):  
F Rizzuti ◽  
G Cescutti ◽  
F Matteucci ◽  
A Chieffi ◽  
R Hirschi ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Galactic Halo ◽  
Massive Stars ◽  
Rotational Behaviour ◽  
Model Data ◽  
Stellar Rotation ◽  
Data Comparison ◽  
Promising Tool ◽  
The Galaxy ◽  
The Mean

ABSTRACT Recent studies show that the chemical evolution of Sr and Ba in the Galaxy can be explained if different production sites, hosting r- and s-processes, are taken into account. However, the question of unambiguously identifying these sites is still unsolved. Massive stars are shown to play an important role in the production of s-material if rotation is considered. In this work, we study in detail the contribution of rotating massive stars to the production of Sr and Ba, in order to explain their chemical evolution, but also to constrain the rotational behaviour of massive stars. A stochastic chemical evolution model was employed to reproduce the enrichment of the Galactic halo. We developed new methods for model-data comparison which help to objectively compare the stochastic results to the observations. We employed these methods to estimate the value of free parameters which describe the rotation of massive stars, assumed to be dependent on the stellar metallicity. We constrain the parameters using the observations for Sr and Ba. Employing these parameters for rotating massive stars in our stochastic model, we are able to correctly reproduce the chemical evolution of Sr and Ba, but also Y, Zr, and La. The data supports a decrease of both the mean rotational velocities and their dispersion with increasing metallicity. Our results show that a metallicity-dependent rotation is a necessary assumption to explain the s-process in massive stars. Our novel methods of model-data comparison represent a promising tool for future galactic chemical evolution studies.

scholarly journals Moving Groups in the Galactic Disc

2013 ◽  
Vol 9 (S298) ◽  
pp. 77-82
Author(s):  
P. Ramya ◽  
B. E. Reddy
Keyword(s):  
Open Clusters ◽  
Galactic Disc ◽  
Chemical Abundance ◽  
Abundance Pattern ◽  
Thick Disc ◽  
Thin Disc ◽  
Stellar Streams ◽  
Moving Groups ◽  
Rule Out

AbstractWe present results of chemical abundance study of a few representative stellar streams of Galactic thick and thin discs. Arcturus stream, which was proposed to have an extragalactic origin, and a recently detected stream called AF06 were studied. Results show a range of metallicity, age and abundance pattern that are consistent with those of Galactic thick disc component. We found similar results for AF06. The abundance and age results unambiguously rule out the possibility that the member stars are vestiges of open clusters. Abundance results of a sample of stars of Sirius and Hercules streams combined with the kinematics show that both the streams belong to the thin disc component. Also, results rule out these are remnants of open clusters. It is likely these streams formed insitu due to perturbations caused by non-axisymmetric components such as bar or spirals.

scholarly journals Mono-enriched stars and Galactic chemical evolution

2020 ◽  
Vol 643 ◽  
pp. A49
Author(s):  
C. J. Hansen ◽  
A. Koch ◽  
L. Mashonkina ◽  
M. Magg ◽  
M. Bergemann ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Second Generation ◽  
Asymptotic Giant Branch ◽  
Three Dimensional Model ◽  
First Stars ◽  
Abundance Pattern ◽  
Abundance Patterns ◽  
The Galaxy ◽  
Bona Fide ◽  
R Process

A long sought after goal using chemical abundance patterns derived from metal-poor stars is to understand the chemical evolution of the Galaxy and to pin down the nature of the first stars (Pop III). Metal-poor, old, unevolved stars are excellent tracers as they preserve the abundance pattern of the gas from which they were born, and hence they are frequently targeted in chemical tagging studies. Here, we use a sample of 14 metal-poor stars observed with the high-resolution spectrograph called the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) to derive abundances of 32 elements (34 including upper limits). We present well-sampled abundance patterns for all stars obtained using local thermodynamic equilibrium (LTE) radiative transfer codes and one-dimensional (1D) hydrostatic model atmospheres. However, it is currently well-known that the assumptions of 1D and LTE may hide several issues, thereby introducing biases in our interpretation as to the nature of the first stars and the chemical evolution of the Galaxy. Hence, we use non-LTE (NLTE) and correct the abundances using three-dimensional model atmospheres to present a physically more reliable pattern. In order to infer the nature of the first stars, we compare unevolved, cool stars, which have been enriched by a single event (“mono-enriched”), with a set of yield predictions to pin down the mass and energy of the Pop III progenitor. To date, only few bona fide second generation stars that are mono-enriched are known. A simple χ2-fit may bias our inferred mass and energy just as much as the simple 1D LTE abundance pattern, and we therefore carried out our study with an improved fitting technique considering dilution and mixing. Our sample presents Carbon Enhanced Metal-Poor (CEMP) stars, some of which are promising bona fide second generation (mono-enriched) stars. The unevolved, dwarf BD+09_2190 shows a mono-enriched signature which, combined with kinematical data, indicates that it moves in the outer halo and likely has been accreted onto the Milky Way early on. The Pop III progenitor was likely of 25.5 M⊙ and 0.6 foe (0.6 1051 erg) in LTE and 19.2 M⊙ and 1.5 foe in NLTE, respectively. Finally, we explore the predominant donor and formation site of the rapid and slow neutron-capture elements. In BD-10_3742, we find an almost clean r-process trace, as is represented in the star HD20, which is a “metal-poor Sun benchmark” for the r-process, while TYC5481-00786-1 is a promising CEMP-r/-s candidate that may be enriched by an asymptotic giant branch star of an intermediate mass and metallicity.

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