Chemo-dynamical signatures in simulated Milky Way-like galaxies

2017 ◽  
Vol 12 (S330) ◽  
pp. 263-264
Author(s):  
Alessandro Spagna ◽  
Anna Curir ◽  
Marco Giammaria ◽  
Mario G. Lattanzi ◽  
Giuseppe Murante ◽  
...  
Keyword(s):  
Milky Way ◽  
Galactic Plane ◽  
Dynamical Evolution ◽  
Thin Disk ◽  
Disk Galaxy ◽  
Radial Gradient ◽  
Heating Mechanism ◽  
Disk Evolution ◽  
Inside Out

AbstractWe have investigated the chemo-dynamical evolution of a Milky Way-like disk galaxy, AqC4, produced by a cosmological simulation integrating a sub-resolution ISM model. We evidence a global inside-out and upside-down disk evolution, that is consistent with a scenario where the “thin disk” stars are formed from the accreted gas close to the galactic plane, while the older “thick disk” stars are originated in situ at higher heights. Also, the bar appears the most effective heating mechanism in the inner disk. Finally, no significant metallicity-rotation correlation has been observed, in spite of the presence of a negative [Fe/H] radial gradient.

scholarly journals Young Stars far from the Galactic Plane: Runaways from Clusters

2004 ◽  
Vol 191 ◽  
pp. 121-127
Author(s):  
Christine Allen ◽  
T.D. Kinman
Keyword(s):  
Star Formation ◽  
Galactic Halo ◽  
Galactic Plane ◽  
Dynamical Evolution ◽  
Young Stars ◽  
Formation Mechanisms ◽  
Conventional View ◽  
Spiral Density Waves ◽  
Ejection Mechanism

AbstractQuite recently, a significant number of OB stars far from the galactic plane have been found, situated at z- distances ranging from several hundreds of pc to several kpc. The short lifetimes of these stars pose problems for their interpretation in terms of the standard picture of star formation. Different mechanisms have been put forward to explain the existence of these stars, either within the conventional view, or postulating star formation in the galactic halo itself. These mechanisms range from arguing that they are misidentified evolved or abnormal stars, to postulating powerful ejection mechanisms for young disk stars; in situ formation also admits several variants. We have collected from the literature a list of young stars far from the plane, for which the evidence of youth seems convincing. We discuss two possible formation mechanisms for these stars: ejection from the plane as the result of dynamical evolution of small clusters (Poveda et al. 1967) and in situ formation, via induced shocks created by spiral density waves (Martos et al. 1999). We compute galactic orbits for these stars, and identify the stars that could be explained by one or the other mechanism. We find that about 90 percent of the stars can be accounted for by the cluster ejection mechanism, that is, they can be regarded as runaway stars in the galactic halo.

Galactic archaeology: Understanding the metallicity gradients with chemo-dynamical models

2018 ◽  
Vol 14 (A30) ◽  
pp. 253-254
Author(s):  
I. Minchev ◽  
F. Anders ◽  
C. Chiappini
Keyword(s):  
Interstellar Medium ◽  
Milky Way ◽  
Cosmic Time ◽  
Dynamical Evolution ◽  
Disk Galaxies ◽  
Dynamical Models ◽  
Disk Formation ◽  
Recent Method ◽  
Gradient Evolution ◽  
Inside Out

AbstractRadial metallicity gradients measured today in the interstellar medium (ISM) and stellar components of disk galaxies are the result of chemo-dynamical evolution since the beginning of disk formation. This makes it difficult to infer the disk past without knowledge of the ISM metallicity gradient evolution with cosmic time. We show that abundance gradients are meaningful only if stellar age information is available. The observed gradient inversion with distance from the disk mid-plane seen in the Milky Way can be explained as the effect of inside-out disk formation and disk flaring of mono-age populations. A novel recent method is presented for constraining the evolution of the Galactic ISM metallicity with radius and time directly from the observations, while at the same time recovering the birth radii of any stellar sample with precise metallicity and age measurements.

scholarly journals A test for radial mixing using local star samples

2012 ◽  
Vol 10 (H16) ◽  
pp. 357-357
Author(s):  
Jincheng Yu ◽  
Jerry Sellwood ◽  
Carlton Pryor ◽  
Li Chen ◽  
Jinliang Hou
Keyword(s):  
Angular Momentum ◽  
Main Sequence ◽  
Milky Way ◽  
Galactic Center ◽  
Thin Disk ◽  
Main Sequence Stars ◽  
Radial Gradient ◽  
Stellar Temperature ◽  
Effective Temperatures ◽  
Constant Gradient

AbstractWe use samples of local main-sequence stars to show that the radial gradient of [Fe/H] in the thin disk of the Milky Way decreases with mean effective stellar temperature. We use the angular momentum of each star about the Galactic center to eliminate the effects of epicyclic motion, which would otherwise blur the estimated gradients. We use the effective temperatures as a proxy for mean age, and conclude that the decreasing gradient is consistent with the predictions of radial mixing due to transient spiral patterns. We find some evidence that the trend of decreasing gradient with increasing mean age breaks to a constant gradient for samples of stars whose main-sequence life-times exceed the likely age of the thin disk.

scholarly journals Evolution of abundance gradients for galactic plane PNe

2009 ◽  
Vol 5 (H15) ◽  
pp. 792-792
Author(s):  
A.F. Kholtygin ◽  
Yu.V. Milanova ◽  
V.V. Akimkin
Keyword(s):  
Milky Way ◽  
Galactic Plane ◽  
Planetary Nebulae ◽  
Thin Disk ◽  
Magellanic Clouds ◽  
Element Abundances

AbstractThe modern observations of planetary nebulae (PNe) are used to recalculate the element abundances for more than 150 PNe of the Milky Way and Magellanic Clouds. Basing on our data, we study the evolution of the abundance gradients for PNe in the thin disk and in the bulge.

scholarly journals VINTERGATAN III: how to reset the metallicity of the Milky Way

2021 ◽  
Vol 503 (4) ◽  
pp. 5868-5876
Author(s):  
Florent Renaud ◽  
Oscar Agertz ◽  
Eric P Andersson ◽  
Justin I Read ◽  
Nils Ryde ◽  
...  
Keyword(s):  
Star Formation ◽  
Milky Way ◽  
Galactic Plane ◽  
First Stars ◽  
Massive Galaxies ◽  
The Galaxy ◽  
Chemical Content ◽  
Major Merger ◽  
Purely Sequential

ABSTRACT Using the cosmological zoom simulation VINTERGATAN, we present a new scenario for the onset of star formation at the metal-poor end of the low-[α/Fe] sequence in a Milky Way-like galaxy. In this scenario, the galaxy is fuelled by two distinct gas flows. One is enriched by outflows from massive galaxies, but not the other. While the former feeds the inner galactic region, the latter fuels an outer gas disc, inclined with respect to the main galactic plane, and with a significantly poorer chemical content. The first passage of the last major merger galaxy triggers tidal compression in the outer disc, which increases the gas density and eventually leads to star formation, at a metallicity 0.75 dex lower than the inner galaxy. This forms the first stars of the low-[α/Fe] sequence. These in situ stars have halo-like kinematics, similar to what is observed in the Milky Way, due to the inclination of the outer disc that eventually aligns with the inner one via gravitational torques. We show that this tilting disc scenario is likely to be common in Milky Way-like galaxies. This process implies that the low-[α/Fe] sequence is populated in situ, simultaneously from two formation channels, in the inner and the outer galaxy, with distinct metallicities. This contrasts with purely sequential scenarios for the assembly of the Milky Way disc and could be tested observationally.

scholarly journals How does the stellar disk of the Milky Way get its gas?

2017 ◽  
Vol 13 (S334) ◽  
pp. 219-222
Author(s):  
Sebastián E. Nuza ◽  
Cristina Chiappini ◽  
Cecilia Scannapieco ◽  
Ivan Minchev ◽  
Marie Martig ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Milky Way ◽  
Thin Disk ◽  
Stellar Disk ◽  
Galactocentric Distance ◽  
Chemical Abundances ◽  
Milky Way Galaxy ◽  
The Galaxy ◽  
History Of ◽  
Inside Out

AbstractIn chemodynamical evolution models it is usually assumed that the Milky Way galaxy forms from the inside-out implying that gas inflows onto the disk decrease with galactocentric distance. Similarly, to reproduce differences between chemical abundances of the thick disk and bulge with respect to those of the thin disk, higher accretion fluxes at early times are postulated. By using a suite of Milky Way-like galaxies extracted from cosmological simulations, we investigate the accretion of gas on the simulated stellar disks during their whole evolution. In general, we find that the picture outlined above holds, although the detailed behavior depends on the assembly history of the Galaxy and the complexities inherent to the physics of galaxy formation.

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 chemical evolution of the Galactic thick and thin disks

2008 ◽  
Vol 4 (S254) ◽  
pp. 191-196 ◽  
Author(s):  
Cristina Chiappini
Keyword(s):  
Chemical Evolution ◽  
Abundance Ratio ◽  
Thin Disk ◽  
Thick Disk ◽  
Disk Evolution ◽  
Gas Accretion ◽  
Main Ideas ◽  
Thin Disks ◽  
Formation Efficiency

AbstractRecent data have revealed a clear distinction between the abundance patterns of the Milky Way (MW) thick and thin disks, suggesting a different origin for each of these components. In this work we first review the main ideas on the formation of the thin disk. From chemical evolution arguments we show that the thin disk should have formed on a long timescale. We also show clear signs that the local stellar samples are contaminated by stars coming from inner radii. We then check what would have to be changed in such a model in order to explain the observables in the thick disk. We find that a model in which the thick disk forms on a much shorter timescale than thin disk and with a star formation efficiency of around a factor of 10 larger than that in the thin disk can account for the observed abundance ratio shifts of several elements between thick and thin disk stars. Moreover, the lack of scatter in the abundance ratio patterns of both the thick and thin disks suggest both components to have been formed in situ by gas accretion and not by mergers of smaller stellar systems. Especially for the thick disk, this last constraint becomes a strong one if its metallicity distribution extends to, at least, solar. Finally, we briefly discuss the interplay between present deuterium abundance and present infall rates in connection with the thin disk evolution.

scholarly journals Stellar orbital properties as diagnostics of the origin of the stellar halo

2015 ◽  
Vol 11 (S317) ◽  
pp. 358-359
Author(s):  
Monica Valluri ◽  
Sarah R. Loebman ◽  
Jeremy Bailin ◽  
Adam Clarke ◽  
Victor P. Debattista ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Milky Way ◽  
Large Fraction ◽  
Disk Galaxy ◽  
Short Axis ◽  
Halo Stars ◽  
The Galaxy ◽  
Stellar Halo

AbstractWe examine metallicities, ages and orbital properties of halo stars in a Milky-Way like disk galaxy formed in the cosmological hydrodynamical MaGICC simulations. Halo stars were either accreted from satellites or they formed in situ in the disk or bulge of the galaxy and were then kicked up into the halo (“in situ/kicked-up” stars). Regardless of where they formed both types show surprisingly similar orbital properties: the majority of both types are on short-axis tubes with the same sense of rotation as the disk – implying that a large fraction of satellites are accreted onto the halo with the same sense of angular momentum as the disk.

scholarly journals Remarkable Symmetries in the Milky Way Disc's Magnetic Field

2011 ◽  
Vol 28 (2) ◽  
pp. 171-176 ◽  
Author(s):  
P. P. Kronberg ◽  
K. J. Newton-McGee
Keyword(s):  
Magnetic Structure ◽  
Large Scale ◽  
Milky Way ◽  
Galactic Center ◽  
Galactic Plane ◽  
Galactic Disk ◽  
Field Structure ◽  
Field Pattern ◽  
Close Coupling ◽  
Sign Change

AbstractWe apply a new, expanded compilation of extragalactic source Faraday rotation measures (RM) to investigate the broad underlying magnetic structure of the Galactic disk at latitudes ∣b∣ ≲15° over all longitudes l, where our total number of RMs is comparable to those in the combined Canadian Galactic Plane Survey (CGPS) at ∣b∣ < 4° and the Southern Galactic Plane (SGPS) ∣b∣<1.5°. We report newly revealed, remarkably coherent patterns of RM at ∣b∣≲15° from l∼270° to ∼90° and RM(l) features of unprecedented clarity that replicate in l with opposite sign on opposite sides of the Galactic center. They confirm a highly patterned bisymmetric field structure toward the inner disc, an axisymmetic pattern toward the outer disc, and a very close coupling between the CGPS/SGPS RMs at ∣b∣≲3° (‘mid-plane’) and our new RMs up to ∣b∣∼15° (‘near-plane’). Our analysis also shows the vertical height of the coherent component of the disc field above the Galactic disc's mid-plane—to be ∼1.5 kpc out to ∼6 kpc from the Sun. This identifies the approximate height of a transition layer to the halo field structure. We find no RM sign change across the plane within ∣b∣∼15° in any longitude range. The prevailing disc field pattern and its striking degree of large-scale ordering confirm that our side of the Milky Way has a very organized underlying magnetic structure, for which the inward spiral pitch angle is 5.5°±1° at all ∣b∣ up to ∼12° in the inner semicircle of Galactic longitudes. It decreases to ∼0° toward the anticentre.

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