scholarly journals Dynamical Influences of the Last Magellanic Interaction on the Magellanic Clouds

2007 ◽  
Vol 24 (1) ◽  
pp. 21-29 ◽  
Author(s):  
Kenji Bekki ◽  
Masashi Chiba
Keyword(s):  
Distribution Function ◽  
Star Formation ◽  
Magellanic Clouds ◽  
Young Stars ◽  
Spatial Distributions ◽  
Diffuse Halo ◽  
Self Consistent ◽  
Hydrodynamical Interaction ◽  
Tidal Tails ◽  
Metallicity Distribution

AbstractWe investigate the present distributions of gas and young stars in the Large and Small Magellanic Clouds (LMC and SMC) based on fully self-consistent numerical simulations of the Clouds for the last ∼0.8 Gyr. Our principal results, which can be tested against observations, are as follows. The last dynamical and hydrodynamical interaction between the Clouds about ∼0.2 Gyr ago can form the apparently off-center bar and peculiar Hı spirals of the LMC. The present spatial distributions of young stars with ages less than ∼20 Myr in the LMC can be significantly asymmetric and clumpy owing to the interaction. A small but non-negligible fraction of stellar and gaseous components can be transferred from the SMC into the LMC during the interaction to form diffuse halo components around the LMC. The burst of star formation in the SMC can be synchronized with that of the LMC about 0.2 Gyr ago in some models. New stars can form from gas in the SMC's tidal tails, one of which can be observed as the Magellanic Bridge (MB). The metallicity distribution function of new stars in the MB has a peak of [Fe/H] ∼ −0.8, which is significantly smaller than the stellar metallicity of the SMC. Based on these results, we discuss the origin of 30 Doradus, the southern molecular ridge of the LMC, the globular cluster ESO 121-SC03, metal-poor inter-Cloud stars within the MB, and giant Hı holes of the LMC.

scholarly journals Stellar Populations in the Magellanic Clouds

1995 ◽  
Vol 164 ◽  
pp. 153-163 ◽  
Author(s):  
M.W. Feast
Keyword(s):  
Star Formation ◽  
Strong Evidence ◽  
Globular Clusters ◽  
Stellar Populations ◽  
Magellanic Clouds ◽  
Young Stars ◽  
Galaxy Interactions

There seems to be no strong evidence that the young globular clusters in the MC have metallicities differing significantly from the metallicities of MC field stars of the same age. The old globular clusters in the LMC are of the same age as, or slightly younger than, those in the outer halo of our Galaxy. It is suggested that the increase in the SFR in the LMC ~ 4 Gyr ago was related to the collapse of the system to a plane. Evidence for a spread in metallicities amongst young stars in either Cloud remains tentative. There is no strong evidence for bursts of star formation being triggered by LMC-SMC-Galaxy interactions but the possibility is raised that the SFR in the SMC has been strongly affected by this interaction.

scholarly journals Deriving the Metallicity Distribution Function of Galactic Systems

2003 ◽  
Vol 20 (2) ◽  
pp. 189-195 ◽  
Author(s):  
Yeshe Fenner ◽  
Brad K. Gibson
Keyword(s):  
Distribution Function ◽  
Star Formation ◽  
Chemical Evolution ◽  
Thin Disk ◽  
Star Formation History ◽  
Dual Phase ◽  
Formation History ◽  
Stellar Halo ◽  
Star Formation Histories ◽  
Metallicity Distribution

AbstractThe chemical evolution of the Milky Way is investigated using a dual-phase metal-enriched infall model in which primordial gas fuels the earliest epoch of star formation, followed by the ongoing formation of stars from newly accreted gas. The latest metallicity distribution of local K-dwarfs is reproduced by this model, which allows the Galactic thin disk to form from slightly metal-enriched gas with α-element enhancement. Our model predicts ages for the stellar halo and thin disk of 12.5 and 7.4 Gyr respectively, in agreement with empirically determined values. The model presented in this paper is compared with a similar dual-phase infall model from Chiappini et al. (2001). We discuss a degeneracy that enables both models to recover the K-dwarf metallicity distribution while yielding different star formation histories.The metallicity distribution function (MDF) of K-dwarfs is proposed to be more directly comparable to chemical evolution model results than the G-dwarf distribution because lower mass K-dwarfs are less susceptible to stellar evolutionary effects. The K-dwarf MDF should consequently be a better probe of star formation history and provide a stronger constraint to chemical evolution models than the widely used G-dwarf MDF. The corrections that should be applied to a G-dwarf MDF are quantified for the case of the outer halo of NGC 5128.

scholarly journals The age and abundance structure of the stellar populations in the central sub-kpc of the Milky Way

2017 ◽  
Vol 13 (S334) ◽  
pp. 86-89
Author(s):  
T. Bensby ◽  
S. Feltzing ◽  
A. Gould ◽  
J. C. Yee ◽  
J. A. Johnson ◽  
...  
Keyword(s):  
Star Formation ◽  
Milky Way ◽  
Stellar Populations ◽  
Young Stars ◽  
Element Abundance ◽  
Abundance Trends ◽  
Solar Metallicity ◽  
High Fraction ◽  
Subgiant Stars ◽  
Metallicity Distribution

AbstractThe four main findings about the age and abundance structure of the Milky Way bulge based on microlensed dwarf and subgiant stars are: (1) a wide metallicity distribution with distinct peaks at [Fe/H] = -1.09, -0.63, -0.20, +0.12, +0.41; (2) a high fraction of intermediate-age to young stars where at [Fe/H] > 0 more than 35 % are younger than 8 Gyr, (3) several episodes of significant star formation in the bulge 3, 6, 8, and 11 Gyr ago; (4) the ‘knee’ in the α-element abundance trends of the sub-solar metallicity bulge appears to be located at a slightly higher [Fe/H] (about 0.05 to 0.1 dex) than in the local thick disk.

scholarly journals Models for the dynamical evolution of the Magellanic System

2008 ◽  
Vol 4 (S256) ◽  
pp. 105-116
Author(s):  
Kenji Bekki
Keyword(s):  
Galactic Halo ◽  
Dynamical Evolution ◽  
Magellanic Clouds ◽  
Young Stars ◽  
Proper Motions ◽  
Self Consistent ◽  
The Galaxy ◽  
Formation And Evolution ◽  
Magellanic Stream ◽  
Magellanic System

AbstractI discuss the following five selected topics on formation and evolution of the LMC and the SMC based on fully self-consistent chemodynamical simulations of the Magellanic Clouds (MCs): (1) formation of bifurcated gaseous structures and young stars in the Magellanic bridge (MB), (2) formation of the Magellanic stream (MS) due to the tidal interaction between the LMC, the SMC, and the Galaxy within the last 2 Gyrs, (3) origin of the observed kinematical differences between H i gas and stars in the SMC, (4) formation of stellar structures dependent on their ages and metallicities in the LMC, and (5) a new common halo model explaining both the latest HST ACS observations on the proper motions of the LMC and the SMC and the presence of the MS in the Galactic halo. I focus exclusively on the latest developments in numerical simulations on formation and evolution of the Magellanic system.

scholarly journals An overview of the structure and kinematics of the Magellanic Clouds

1991 ◽  
Vol 148 ◽  
pp. 15-23 ◽  
Author(s):  
B. E. Westerlund
Keyword(s):  
Star Formation ◽  
Observational Data ◽  
Spiral Structure ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
Line Of Sight ◽  
Small Magellanic Cloud ◽  
Complex Velocity ◽  
The Past

A vast amount of observational data concerning the structure and kinematics of the Magellanic Clouds is now available. Many basic quantities (e.g. distances and geometry) are, however, not yet sufficiently well determined. Interactions between the Small Magellanic Cloud (SMC), the Large Magellanic Cloud (LMC) and our Galaxy have dominated the evolution of the Clouds, causing bursts of star formation which, together with stochastic self-propagating star formation, produced the observed structures. In the youngest generation in the LMC it is seen as an intricate pattern imitating a fragmented spiral structure. In the SMC much of the fragmentation is along the line of sight complicating the reconstruction of its history. The violent events in the past are also recognizable in complex velocity patterns which make the analysis of the kinematics of the Clouds difficult.

scholarly journals VELOCITY SEGREGATION IN A CLUMP-LIKE OUTFLOW WITH A NON-TOP HAT VELOCITY CROSS-SECTION

2021 ◽  
Vol 57 (2) ◽  
pp. 269-277
Author(s):  
A. Castellanos-Ramírez ◽  
A. C. Raga ◽  
J. Cantó ◽  
A. Rodríguez-González ◽  
L. Hernández-Martínez
Keyword(s):  
Star Formation ◽  
Simple Model ◽  
Radial Velocity ◽  
Cross Section ◽  
High Velocity ◽  
Planetary Nebulae ◽  
Young Stars ◽  
Working Surface ◽  
Star Formation Regions ◽  
Analytic Models

High velocity clumps joined to the outflow source by emission with a “Hubble law” ramp of linearly increasing radial velocity vs. distance are observed in some planetary nebulae and in some outflows in star formation regions. We propose a simple model in which a “clump” is ejected from a source over a period τ0, with a strong axis to edge velocity stratification. This non-top hat cross section results in the production of a highly curved working surface (initially being pushed by the ejected material, and later coasting along due to its inertia). From both analytic models and numerical simulations we find that this working surface has a linear velocity vs. position ramp, and therefore reproduces in a qualitative way the “Hubble law clumps” in planetary nebulae and outflows from young stars.

Star Formation in the Magellanic Clouds: New Insights fromHerschelHERITAGE

2011 ◽  
Vol 52 ◽  
pp. 113-118
Author(s):  
M. Meixner ◽  
M. Sewiło ◽  
F. Galliano ◽  
Keyword(s):  
Star Formation ◽  
Magellanic Clouds
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