Kinematics of the Milky Way Thick disk in solar neighborhood

2021 ◽  
Author(s):  
K. Vieira ◽  
V. Korchagin ◽  
A. Lutsenko
Keyword(s):  
Milky Way ◽  
Galactic Plane ◽  
Thick Disk ◽  
Solar Neighborhood ◽  
Stellar Disk ◽  
The Sun ◽  
Complete Sample ◽  
Two Component ◽  
Thick Disks ◽  
Red Giant

Using GAIA EDR3 catalog, we present the detailed analysis of the two-component Milky Way stellar disk in the solar neighborhood. To determine the kinematical properties of the thin and of the Thick disks, we select the complete sample of about 278,000 evolved red giant branch (RGB) stars distributed in the cylinder of 1 kpc radius and 0.5 kpc height centered at the Sun. We measured the following mean velocities and dispersions for the thin and the Thick disks, respectively: [Formula: see text][Formula: see text]km s[Formula: see text] with [Formula: see text][Formula: see text]km s[Formula: see text], and [Formula: see text][Formula: see text]km s[Formula: see text] with [Formula: see text][Formula: see text]km s[Formula: see text]. Errors in mean velocities and dispersions are all less than 1[Formula: see text]km s[Formula: see text]. Same values were computed on much smaller subsamples of our Gaia data with RAVE DR5 [Fe/H] values, from which a metallicity selection was added. Results are basically the same. We find that up to 500 pc height above/below the galactic plane, Thick disk stars comprise about half the stars of the disk. We also find evidence of a substructure in [Formula: see text] versus [Formula: see text] in the thick disk population mostly that would give support to the accretion scenario for the formation of the thick 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 Exploration of Galactic Structures beyond the Sun toward the anti-center of the Milky Way

2013 ◽  
Vol 9 (S298) ◽  
pp. 450-450
Author(s):  
Yan Xu ◽  
Heidi Newberg
Keyword(s):  
Milky Way ◽  
Galactic Plane ◽  
Wave Structure ◽  
Thin Disk ◽  
Thick Disk ◽  
The Sun ◽  
The South ◽  
The North ◽  
Metallicity Distribution ◽  
Kinematic Distribution

AbstractWe map the stellar distribution on Hess diagram in the Anti-Center roughly in the boxes 130<l<230, −30<b<−10 and 10<b<30. There are ‘extra components’ associated with the anti-center structures of figure 1 of Newberg et al. (2002). The turnoff point of the structure in the North sky is at 16m.5 and the turnoff point in the South is at 17m.5. In our work, these structures can be found in all of the longitude in our box that can't be explained by standard thin or thick disk models. The distance of the North structure is about 2 kpc (we call it the North near structure) and the galactic height is about 0.7 kpc, the distance of the South structure is about 4 – 6 kpc (we call it the South middle structure). The Vgsr distribution of stars selected along the North near structure has a kinematic distribution similar to that of thick disk stars. But the metallicities of these stars are quite similar to the metallicity distribution of thin disk stars. We try to explain these structures with wave structure of the Galactic plane.

scholarly journals The Canis Major Dwarf Galaxy

2004 ◽  
Vol 21 (4) ◽  
pp. 371-374
Author(s):  
Geraint F. Lewis ◽  
Rodrigo A. Ibata ◽  
Michael J. Irwin ◽  
Nicolas F. Martin ◽  
Michele Bellazzini ◽  
...  
Keyword(s):  
Building Block ◽  
Milky Way ◽  
Galactic Halo ◽  
Galactic Plane ◽  
Dwarf Galaxy ◽  
Observational Evidence ◽  
Thick Disk ◽  
Equatorial Orbit ◽  
Satellite Galaxy

AbstractRecent observational evidence suggests that the Sagittarius dwarf galaxy represents the only major ongoing accretion event in the Galactic halo, accounting for the majority of stellar debris identified there. This paper summarises the recent discovery of another potential Milky Way accretion event, the Canis Major dwarf galaxy. This dwarf satellite galaxy is found to lie just below the Galactic plane and appears to be on an equatorial orbit. Unlike Sagittarius, which is contributing to the Galactic halo, the location and eventual demise of Canis Major suggests that it represents a building block of the thick disk.

scholarly journals The Gaia-ESO Survey: Churning through the Milky Way

2018 ◽  
Vol 609 ◽  
pp. A79 ◽  
Author(s):  
M. R. Hayden ◽  
A. Recio-Blanco ◽  
P. de Laverny ◽  
S. Mikolaitis ◽  
G. Guiglion ◽  
...  
Keyword(s):  
Milky Way ◽  
Past History ◽  
Stellar Populations ◽  
Solar Neighborhood ◽  
The Sun ◽  
Radial Migration ◽  
Orbital Parameters ◽  
The Past ◽  
Major Merger ◽  
History Of

Context. There have been conflicting results with respect to the extent that radial migration has played in the evolution of the Galaxy. Additionally, observations of the solar neighborhood have shown evidence of a merger in the past history of the Milky Way that drives enhanced radial migration. Aims. We attempt to determine the relative fraction of stars that have undergone significant radial migration by studying the orbital properties of metal-rich ([Fe/H] > 0.1) stars within 2 kpc of the Sun. We also aim to investigate the kinematic properties, such as velocity dispersion and orbital parameters, of stellar populations near the Sun as a function of [Mg/Fe] and [Fe/H], which could show evidence of a major merger in the past history of the Milky Way. Methods. We used a sample of more than 3000 stars selected from the fourth internal data release of the Gaia-ESO Survey. We used the stellar parameters from the Gaia-ESO Survey along with proper motions from PPMXL to determine distances, kinematics, and orbital properties for these stars to analyze the chemodynamic properties of stellar populations near the Sun. Results. Analyzing the kinematics of the most metal-rich stars ([Fe/H] > 0.1), we find that more than half have small eccentricities (e< 0.2) or are on nearly circular orbits. Slightly more than 20% of the metal-rich stars have perigalacticons Rp> 7 kpc. We find that the highest [Mg/Fe], metal-poor populations have lower vertical and radial velocity dispersions compared to lower [Mg/Fe] populations of similar metallicity by ~10 km s-1. The median eccentricity increases linearly with [Mg/Fe] across all metallicities, while the perigalacticon decreases with increasing [Mg/Fe] for all metallicities. Finally, the most [Mg/Fe]-rich stars are found to have significant asymmetric drift and rotate more than 40 km s-1 slower than stars with lower [Mg/Fe] ratios. Conclusions. While our results cannot constrain how far stars have migrated, we propose that migration processes are likely to have played an important role in the evolution of the Milky Way, with metal-rich stars migrating from the inner disk toward to solar neighborhood and past mergers potentially driving enhanced migration of older stellar populations in the disk.

scholarly journals The Flare and Warp of the Young Stellar Disk Traced with LAMOST DR5 OB-type Stars

2021 ◽  
Vol 922 (1) ◽  
pp. 80
Author(s):  
Yang Yu ◽  
Hai-Feng Wang ◽  
Wen-Yuan Cui ◽  
Lin-Lin Li ◽  
Chao Liu ◽  
...  
Keyword(s):  
Galactic Plane ◽  
Scale Height ◽  
Stellar Disk ◽  
Spatial Density ◽  
Galactocentric Distance ◽  
Secular Evolution ◽  
The North ◽  
Red Giant ◽  
Almost All ◽  
North And South

Abstract We present an analysis of the spatial density structure for the outer disk from 8–14 kpc with the LAMOST DR5 13,534 OB-type stars and observe similar flaring on the north and south sides of the disk, implying that the flaring structure is symmetrical about the Galactic plane, for which the scale height at different Galactocentric distances is from 0.14 to 0.5 kpc. By using the average slope to characterize the flaring strength, we find that the thickness of the OB stellar disk is similar but that flaring is slightly stronger compared to the thin disk as traced by red giant branch stars, possibly implying that secular evolution is not the main contributor to the flaring but rather perturbation scenarios such as interactions with passing dwarf galaxies could be possible. When comparing the scale height of the OB stellar disk on the north and south sides with the gas disk, the former one is slightly thicker than the latter one by ≈33 and 9 pc, meaning that one could tentatively use young OB-type stars to trace the gas properties. Meanwhile, we determine that the radial scale length of the young OB stellar disk is 1.17 ± 0.05 kpc, which is shorter than that of the gas disk, confirming that the gas disk is more extended than the stellar disk. What is more, by considering the midplane displacements (Z 0) in our density model we find that almost all values of Z 0 are within 100 pc, with an increasing trend as Galactocentric distance increases.

scholarly journals Predicción probabilística de la existencia de estrellas Cefeidas en la galaxia

2019 ◽  
Vol 65 (1) ◽  
pp. 34
Author(s):  
A. Cabañas Hernández ◽  
D. L. Cárdenas ◽  
E. E. Damián de la Cruz ◽  
A. Fortiz Flores ◽  
L. E. Garduño Puga ◽  
...  
Keyword(s):  
Probability Density Function ◽  
Probability Density ◽  
Milky Way ◽  
Solar Neighborhood ◽  
The Sun ◽  
Concentration Zone ◽  
High Concentration ◽  
Normal Probability ◽  
The Galaxy ◽  
Probabilistic Study

Las estrellas Cefeidas han sido de gran relevancia para la determinación de distancias tanto en la Galaxia como a escala cosmológica. Debido a que, hasta el momento, la mayor parte de las Cefeidas cercanas observadas se encuentran en la vecindad solar, se juzga pertinente un estudio probabilístico sobre su distribución, no solo en la vecindad solar sino también en toda la Vía Láctea, pues deben estar jugando un papel importante para mantener la estructura de nuestra Galaxia. Partiendo de 187 Cefeidas observadas en la Vía Láctea, se presenta una función de densidad de probabilidad normal que sirvió para elaborar un modelo en tres dimensiones que permite encontrar la zona de más alta concentración de Cefeidas y de paso, con ella, predecir la existencia de Cefeidas en zonas ceranas a toda la Galaxia. Asmismo, se da a conocer una segunda distribución de probabilidad, normal también, pero en la vecindad del eje galáctico, a fin de elaborar otro modelo que permita predecir la existencia de estrellas Cefeidas dentro de la Vía Láctea y en la vecindad del sol.ABSTRACTThe Cepheid stars have been very relevant for the determination ofdistances both in the Galaxy and also at cosmological scale. Because, so far, most of the nearby observed Cepheids are in the solar neighborhood, a probabilistic study about their distribution in the solar neighborhood and in the whole Milky Way is pertinent, since they must be playing an important role for keeping the structure of our Galaxy. Starting from the in the Milky Way already 187 observed Cepheids, a normal probability density function for their distribution in the Galaxy is presented, which is used to carry out a model which allows to find the high concentration zone of Cepheids and, in turn, with it, to predict the existence of Cepheids in the neighborhood of the Galaxy. A second model has been done, in order to prognosticate the existence of Cepheids within the milky way and in the neigborhood of the sun.

scholarly journals Structure and Evolution of the Milky Way Galaxy

1989 ◽  
Vol 111 ◽  
pp. 83-102 ◽  
Author(s):  
Gerard Gilmore ◽  
Rosemary F.G. Wyse
Keyword(s):  
Globular Cluster ◽  
Milky Way ◽  
Axial Ratio ◽  
Thick Disk ◽  
The Sun ◽  
Chemical Abundance ◽  
Milky Way Galaxy ◽  
The Galaxy ◽  
Globular Cluster System ◽  
Available Information

AbstractThe combination of chemical abundance, kinematic, and age data for stars near the sun provides important information about the early evolution of the Galaxy. We review available data, with some new analysis, to show that the sum of all available information strongly suggests that the extreme population II subdwarf system formed during a period of rapid collapse of the proto-Galaxy. This subdwarf system now forms a flattened, pressure-supported distribution, with axial ratio ∼2:1. The thick disk formed subsequent to the subdwarf system. At least the metal-poor tail of the thick disk is comparable in age to the globular cluster system. The thick disk is probably kinematically discrete from the Galactic old disk, though the data remain inadequate for robust conclusions.

scholarly journals New constraints on the structure of the nuclear stellar cluster of the Milky Way from star counts and MIR imaging

2020 ◽  
Vol 634 ◽  
pp. A71 ◽  
Author(s):  
E. Gallego-Cano ◽  
R. Schödel ◽  
F. Nogueras-Lara ◽  
H. Dong ◽  
B. Shahzamanian ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Milky Way ◽  
Galactic Center ◽  
Galactic Plane ◽  
3D Structure ◽  
Major Axis ◽  
Stellar Disk ◽  
Axis Ratio ◽  
Stellar Cluster ◽  
Red Clump

Context. The Milky Way nuclear star cluster (MWNSC) is a crucial laboratory for studying the galactic nuclei of other galaxies, but its properties have not been determined unambiguously until now. Aims. We aim to study the size and spatial structure of the MWNSC. Methods. This study uses data and methods that address potential shortcomings of previous studies on the topic. We use 0.2″ angular resolution Ks data to create a stellar density map in the central 86.4 pc × 21 pc at the Galactic center. We include data from selected adaptive-optics-assisted images obtained for the inner parsecs. In addition, we use Spitzer/IRAC mid-infrared (MIR) images. We model the Galactic bulge and the nuclear stellar disk in order to subtract them from the MWNSC. Finally, we fit a Sérsic model to the MWNSC and investigate its symmetry. Results. Our results are consistent with previous work. The MWNSC is flattened with an axis ratio of q = 0.71 ± 0.10, an effective radius of Re = (5.1 ± 1.0) pc, and a Sérsic index of n = 2.2 ± 0.7. Its major axis may be tilted out of the Galactic plane by up to −10°. The distribution of the giants brighter than the Red Clump (RC) is found to be significantly flatter than the distribution of the faint stars. We investigate the 3D structure of the central stellar cusp using our results on the MWNSC structure on large scales to constrain the deprojection of the measured stellar surface number density, obtaining a value of the 3D inner power law of γ = 1.38 ± 0.06sys ± 0.01stat. Conclusions. The MWNSC shares its main properties with other extragalactic NSCs found in spiral galaxies. The differences in the structure between bright giants and RC stars might be related to the existence of not completely mixed populations of different ages. This may hint at recent growth of the MWNSC through star formation or cluster accretion.

scholarly journals Exploring the production and depletion of lithium in the Milky Way stellar disk

2018 ◽  
Vol 615 ◽  
pp. A151 ◽  
Author(s):  
Thomas Bensby ◽  
Karin Lind
Keyword(s):  
Milky Way ◽  
Signal To Noise Ratio ◽  
Thin Disk ◽  
Thick Disk ◽  
Stellar Disk ◽  
Steady Increase ◽  
High Signal ◽  
Unique Element ◽  
Chemical Enrichment ◽  
Upper Limits

Despite the recent availability of large samples of stars with high-precision Li abundances, there are many unanswered questions about the evolution of this unique element in the Galaxy and in the stars themselves. It is unclear which parameters and physical mechanisms govern Li depletion in late-type stars and if Galactic enrichment has proceeded differently in different stellar populations. With this study we aim to explore these questions further by mapping the evolution of Li with stellar mass, age, and effective temperature for Milky Way disk stars, linking the metal-poor and metal-rich regimes, and how Li differs in the thin and thick disks. We determine Li abundances for a well-studied sample of 714 F and G dwarf, turn-off, and subgiant stars in the solar neighbourhood. The analysis is based on line synthesis of the 7Li line at 6707 Å in high-resolution and high-signal-to-noise ratio echelle spectra, obtained with the MIKE, FEROS, SOFIN, UVES, and FIES spectrographs. The presented Li abundances are corrected for non-LTE effects. Out of the sample of 714 stars, we are able to determine Li abundances for 394 stars and upper limits on the Li abundance for another 121 stars. Out of 36 stars that are listed as exoplanet host stars, 18 have well-determined Li abundances and 6 have Li upper limits. Our main finding is that there are no signatures of Li production in stars associated with the thick disk. Instead the Li abundance trend is decreasing with metallicity for these thick disk stars. Significant Li production is however seen in the thin disk, with a steady increase towards super-solar metallicities. At the highest metallicities, however, around [Fe/H] ≈ +0.3, we tentatively confirm the recent discovery that the Li abundances level out. Our finding contradicts the other recent studies that found that Li is also produced in the thick disk. We find that this is likely due to the α-enhancement criteria which those studies used to define their thick disk samples. By using the more robust age criteria, we are able to define a thick disk stellar sample that is much less contaminated by thin disk stars. Furthermore, we also tentatively confirm the age-Li correlation for solar twin stars, and we find that there is no correlation between Li abundance and whether the stars have detected exoplanets or not. The major conclusion that can be drawn from this study is that no significant Li production relative to the primordial abundance took place during the first few billion years of the Milky Way, an era coinciding with the formation and evolution of the thick disk. Significant Li enrichment then took place once long-lived low-mass stars (acting on a timescale longer than SNIa) had had time to contribute to the chemical enrichment of the interstellar medium.

scholarly journals The age of the Galaxy's thick disk

2008 ◽  
Vol 4 (S258) ◽  
pp. 23-30 ◽  
Author(s):  
Sofia Feltzing ◽  
Thomas Bensby
Keyword(s):  
Age Distribution ◽  
Thin Disk ◽  
Thick Disk ◽  
Solar Neighborhood ◽  
Age Dating ◽  
Preliminary Results ◽  
Giant Stars ◽  
Elemental Abundances ◽  
Thick Disks ◽  
Effective Temperatures

AbstractWe discuss the age of the stellar disks in the solar neighborhood. After reviewing the various methods for age dating, we discuss current estimates of the ages of both the thin- and the thick disks. We present preliminary results for kinematically-selected stars that belong to the thin- as well as the thick disk. All of these dwarf and sub-giant stars have been studied spectroscopically and we have derived both elemental abundances as well as ages for them. A general conclusion is that in the solar neighborhood, on average, the thick disk is older than the thin disk. However, we caution that the exclusion of stars with effective temperatures around 6500 K might result in a biased view of the full age distribution for the stars in the thick disk.

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