scholarly journals Galaxy simulations in the Gaia era

2017 ◽  
Vol 12 (S330) ◽  
pp. 127-135
Author(s):  
Ivan Minchev
Keyword(s):  
Chemical Composition ◽  
Numerical Simulations ◽  
Spectroscopic Data ◽  
Milky Way ◽  
Disk Galaxies ◽  
Physical Processes ◽  
Radial Migration ◽  
Cosmological Context ◽  
Enormous Amount ◽  
Formation And Evolution

AbstractWe live in an age where an enormous amount of astrometric, photometric, asteroseismic, and spectroscopic data of Milky Way stars are being acquired, many orders of magnitude larger than about a decade ago. Thanks to the Gaia astrometric mission and followup ground-based spectroscopic surveys in the next 5-10 years about 10-20 Million stars will have accurate 6D kinematics and chemical composition measurements. KEPLER-2, PLATO, and TESS will provide asteroseismic ages for a good fraction of those. In this article we outline some outstanding problems concerning the formation and evolution of the Milky Way and argue that, due to the complexity of physical processes involved in the formation of disk galaxies, numerical simulations in the cosmological context are needed for the interpretation of Milky Way observations. We also discuss in some detail the formation of the Milky Way thick disk, chemodynamical models, and the effects of radial migration.

scholarly journals Radial migration in barred galaxies

2012 ◽  
Vol 10 (H16) ◽  
pp. 355-355
Author(s):  
P. Di Matteo ◽  
M. Haywood ◽  
F. Combes ◽  
B. Semelin ◽  
C. Babusiaux ◽  
...  
Keyword(s):  
High Resolution ◽  
Numerical Simulations ◽  
Disk Galaxies ◽  
List Type ◽  
Stellar Content ◽  
Radial Migration ◽  
Barred Galaxies ◽  
Corotation Radius ◽  
Low Activity ◽  
Metallicity Distribution

AbstractIn this talk, I will present the result of high resolution numerical simulations of disk galaxies with various bulge/disk ratios evolving isolated, showing that: •Most of migration takes place when the bar strength is high and decreases in the phases of low activity (in agreement with the results by Brunetti et el. 2011, Minchev et al. 2011).•Most of the stars inside the corotation radius (CR) do not migrate in the outer regions, but stay confined in the inner disk, while stars outside CR can migrate either inwards or outwards, diffusing over the whole disk.•Migration is accompanied by significative azimuthal variations in the metallicity distribution, of the order of 0.1 dex for an initial gradient of ~-0.07 dex/kpc.•Boxy bulges are an example of stellar structures whose properties (stellar content, vertical metallicity, [α/Fe] and age gradients, ..) are affected by radial migration (see also Fig. 1).

scholarly journals Evidence from APOGEE for the presence of a major building block of the halo buried in the inner Galaxy

2020 ◽  
Vol 500 (1) ◽  
pp. 1385-1403 ◽  
Author(s):  
Danny Horta ◽  
Ricardo P Schiavon ◽  
J Ted Mackereth ◽  
Joel Pfeffer ◽  
Andrew C Mason ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Numerical Simulations ◽  
Early Life ◽  
Milky Way ◽  
Stellar Structure ◽  
Galactic Centre ◽  
Galaxy Structure ◽  
Elemental Abundances ◽  
Low Mass ◽  
The Mean

ABSTRACT We report evidence from APOGEE for the presence of a new metal-poor stellar structure located within ∼4 kpc of the Galactic Centre. Characterized by a chemical composition resembling those of low-mass satellites of the Milky Way, this new inner Galaxy structure (IGS) seems to be chemically and dynamically detached from more metal-rich populations in the inner Galaxy. We conjecture that this structure is associated with an accretion event that likely occurred in the early life of the Milky Way. Comparing the mean elemental abundances of this structure with predictions from cosmological numerical simulations, we estimate that the progenitor system had a stellar mass of ∼5 × 108 M⊙, or approximately twice the mass of the recently discovered Gaia-Enceladus/Sausage system. We find that the accreted:in situ ratio within our metal-poor ([Fe/H] < –0.8) bulge sample is somewhere between 1:3 and 1:2, confirming predictions of cosmological numerical simulations by various groups.

Disk Galaxies in the Magneticum Pathfinder Simulations

2014 ◽  
Vol 10 (S309) ◽  
pp. 145-148 ◽  
Author(s):  
Rhea-Silvia Remus ◽  
Klaus Dolag ◽  
Lisa K. Bachmann ◽  
Alexander M. Beck ◽  
Andreas Burkert ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Mass Function ◽  
Disk Galaxies ◽  
Physical Processes ◽  
Galaxy Formation And Evolution ◽  
Mass Size ◽  
Formation And Evolution ◽  
Galaxy Populations ◽  
Size Relation ◽  
The Universe

AbstractWe presentMagneticum Pathfinder, a new set of hydrodynamical cosmological simulations covering a large range of cosmological scales. Among the important physical processes included in the simulations are the chemical and thermodynamical evolution of the diffuse gas as well as the evolution of stars and black holes and the corresponding feedback channels. In the high resolution boxes aimed at studies of galaxy formation and evolution, populations of both disk and spheroidal galaxies are self-consistently reproduced. These galaxy populations match the observed stellar mass function and show the same trends for disks and spheroids in the mass–size relation as observations from the SDSS. Additionally, we demonstrate that the simulated galaxies successfully reproduce the observed specific angular-momentum–mass relations for the two different morphological types of galaxies. In summary, theMagneticum Pathfindersimulations are a valuable tool for studying the assembly of cosmic and galactic structures in the universe.

scholarly journals Traits for chemical evolution in solar twins

2020 ◽  
Vol 633 ◽  
pp. L9 ◽  
Author(s):  
Paula Jofré ◽  
Holly Jackson ◽  
Marcelo Tucci Maia
Keyword(s):  
Chemical Evolution ◽  
Milky Way ◽  
Chemical Elements ◽  
Abundance Ratio ◽  
Time Dependency ◽  
Physical Processes ◽  
Low Mass ◽  
Formation And Evolution ◽  
Process Elements ◽  
Space Phase

The physical processes driving chemical evolution in the Milky Way can be probed using the distribution of abundances in low-mass FGK type stars in space phase at different times. During their final stages of evolution, stars experience nucleosynthesis several times, each at different timescales and producing different chemical elements. Finding abundance ratios that have simple variations across cosmic times therefore remains a challenge. Using the sample of 80 solar twins for which ages and abundances of 30 elements have been measured with high precision, we searched for all possible abundance ratio combinations that show linear trends with age. We found 55 such ratios, all combining an n-capture element and another element produced by different nucleosynthesis channels. We recovered the ratios of [Y/Mg], [Ba/Mg], and [Al/Y] that have been reported previously in the literature, and found that [C/Ba] depends most strongly on age, with a slope of 0.049 ± 0.003 dex Gyr−1. This imposes constraints on the magnitude of the time dependency of abundance ratios in solar twins. Our results suggest that s-process elements, in lieu of Fe, should be used as a reference for constraining chemical evolution models of the solar neighbourhood. Our study illustrates that a wide variety of chemical elements measured in high-resolution spectra is key to meeting the current challenges in understanding the formation and evolution of our Galaxy.

Simulations of MW-mass galaxies in the cosmological context

2017 ◽  
Vol 13 (S334) ◽  
pp. 201-208
Author(s):  
Cecilia Scannapieco
Keyword(s):  
Angular Momentum ◽  
Environmental Effects ◽  
Milky Way ◽  
Local Group ◽  
Initial Conditions ◽  
Cosmic Time ◽  
Cosmological Context ◽  
Formation And Evolution

AbstractDuring the last three decades simulations of the formation of galaxies have made fantastic progress, overcoming problems such as the angular momentum catastrophe and producing galaxies that resemble disk-bulge systems similar to those observed. In this work, I discuss such progress focusing on the formation and evolution of disks in galaxies similar to our Milky Way, and on the effects of different feedback processes that affect galaxies through cosmic time.I also present the results of simulations that use constrained initial conditions of the Local Group, and discuss environmental effects that might play a role in the formation and evolution of our Galaxy.

scholarly journals Radial migration in numerical simulations of Milky-Way sized galaxies

2016 ◽  
Vol 337 (8-9) ◽  
pp. 957-960 ◽  
Author(s):  
R. J. J. Grand ◽  
D. Kawata
Keyword(s):  
Numerical Simulations ◽  
Milky Way ◽  
Radial Migration

scholarly journals The Galactic bulge: a review

2007 ◽  
Vol 3 (S245) ◽  
pp. 323-332 ◽  
Author(s):  
Dante Minniti ◽  
Manuela Zoccali
Keyword(s):  
Chemical Composition ◽  
Central Region ◽  
Milky Way ◽  
Galactic Center ◽  
Current Understanding ◽  
Ir Detectors ◽  
Individual Stars ◽  
Near Ir ◽  
Great Progress ◽  
Formation And Evolution

AbstractThe Milky Way is the only galaxy for which we can resolve individual stars at all evolutionary phases, from the Galactic center to the outskirt. The last decade, thanks to the advent of near IR detectors and 8 meter class telescopes, has seen a great progress in the understanding of the Milky Way central region: the bulge. Here we review the most recent results regarding the bulge structure, age, kinematics and chemical composition. These results have profound implications for the formation and evolution of the Milky Way and of galaxies in general. This paper provides a summary on our current understanding of the Milky Way bulge, intended mainly for workers on other fields.

scholarly journals The GALAH survey: tracing the Galactic disk with open clusters

2021 ◽  
Author(s):  
Lorenzo Spina ◽  
Yuan-Sen Ting ◽  
Gayandhi M De Silva ◽  
Neige Frankel ◽  
Sanjib Sharma ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Spectroscopic Data ◽  
Galactic Disk ◽  
Chemical Elements ◽  
Selection Effect ◽  
Open Clusters ◽  
High Quality ◽  
Radial Migration ◽  
History Of ◽  
Chemical Distribution

Abstract Open clusters are unique tracers of the history of our own Galaxy’s disk. According to our membership analysis based on Gaia astrometry, out of the 226 potential clusters falling in the footprint of GALAH or APOGEE, we find that 205 have secure members that were observed by at least one of the survey. Furthermore, members of 134 clusters have high-quality spectroscopic data that we use to determine their chemical composition. We leverage this information to study the chemical distribution throughout the Galactic disk of 21 elements, from C to Eu. The radial metallicity gradient obtained from our analysis is −0.076 ± 0.009 dex kpc−1, which is in agreement with previous works based on smaller samples. Furthermore, the gradient in the [Fe/H] - guiding radius (rguid) plane is −0.073 ± 0.008 dex kpc−1. We show consistently that open clusters trace the distribution of chemical elements throughout the Galactic disk differently than field stars. In particular, at given radius, open clusters show an age-metallicity relation that has less scatter than field stars. As such scatter is often interpreted as an effect of radial migration, we suggest that these differences are due to the physical selection effect imposed by our Galaxy: clusters that would have migrated significantly also had higher chances to get destroyed. Finally, our results reveal trends in the [X/Fe]-rguid-age space, which are important to understand production rates of different elements as a function of space and time.

scholarly journals An Atmospheric Origin for HCN-Derived Polymers on Titan

Processes ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 965
Author(s):  
Zoé Perrin ◽  
Nathalie Carrasco ◽  
Audrey Chatain ◽  
Lora Jovanovic ◽  
Ludovic Vettier ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Gas Phase ◽  
Formation Process ◽  
Upper Atmosphere ◽  
Gas Mixture ◽  
Space Probe ◽  
Atmospheric Haze ◽  
Formation And Evolution ◽  
Haze Formation

Titan’s haze is strongly suspected to be an HCN-derived polymer, but despite the first in situ measurements by the ESA-Huygens space probe, its chemical composition and formation process remain largely unknown. To investigate this question, we simulated the atmospheric haze formation process, experimentally. We synthesized analogues of Titan’s haze, named Titan tholins, in an irradiated N2–CH4 gas mixture, mimicking Titan’s upper atmosphere chemistry. HCN was monitored in situ in the gas phase simultaneously with the formation and evolution of the haze particles. We show that HCN is produced as long as the particles are absent, and is then progressively consumed when the particles appear and grow. This work highlights HCN as an effective precursor of Titan’s haze and confirms the HCN-derived polymer nature of the haze.

scholarly journals Radial metallicity gradients with Galactic nebular probes

2018 ◽  
Vol 14 (A30) ◽  
pp. 240-241 ◽  
Author(s):  
Jorge García-Rojas
Keyword(s):  
Milky Way ◽  
Galactic Disc ◽  
Formation And Evolution

AbstractThe study of radial metallicity gradients in the disc of the Milky Way is a powerful tool to understand the mechamisms that have been acting in the formation and evolution of the Galactic disc. In this proceeding, I will put the eye on some problems that should be carefully addressed to obtain precise determinations of the metallicity gradients.

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