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 Spatial variations in the star formation history of the Large Magellanic Cloud

2008 ◽  
Vol 4 (S256) ◽  
pp. 281-286
Author(s):  
Carme Gallart ◽  
Ingrid Meschin ◽  
Antonio Aparicio ◽  
Peter B. Stetson ◽  
Sebastián L. Hidalgo
Keyword(s):  
Star Formation ◽  
Outer Part ◽  
Large Magellanic Cloud ◽  
Star Formation History ◽  
Wide Field ◽  
Galactocentric Distance ◽  
Formation History ◽  
The Galaxy ◽  
History Of ◽  
Star Formation Histories

AbstractBased on the quantitative analysis of a set of wide-field color—magnitude diagrams reaching the old main sequence-turnoffs, we present new LMC star-formation histories, and their variation with galactocentric distance. Some coherent features are found, together with systematic variations of the star-formation history among the three fields analyzed. We find two main episodes of star formation in all three fields, from 1 to 4 and 7 to 13 Gyr ago, with relatively low star formation around ≃ 4–7 Gyr ago. The youngest age in each field gradually increases with galactocentric radius; in the innermost field, LMC 0514–6503, an additional star formation event younger than 1 Gyr is detected, with star formation declining, however, in the last ≃ 200 Myr. The population is found to be older on average toward the outer part of the galaxy, although star formation in all fields seems to have started around 13 Gyr ago.

scholarly journals Dynamical and Chemical Evolution of IZw18

2004 ◽  
Vol 21 (2) ◽  
pp. 157-160
Author(s):  
Simone Recchi
Keyword(s):  
Star Formation ◽  
Chemical Evolution ◽  
Dwarf Galaxy ◽  
Star Formation History ◽  
Intermediate Mass ◽  
Intermediate Mass Stars ◽  
Formation History ◽  
Type Ia ◽  
Ia Supernovae ◽  
Detailed Chemical

AbstractWe study the effect of different star formation regimes on the dynamical and chemical evolution of IZw18, the most metal-poor dwarf galaxy locally known. To do that we adopt a two-dimensional hydrocode coupled with detailed chemical yields originating from Type II and Type Ia supernovae and from intermediate-mass stars. Particular emphasis is devoted to the problem of mixing of metals. We conclude that, under particular conditions, cooling of metals occurs with a timescale of the order of 10 Myr, thus confirming the hypothesis of instantaneous mixing adopted in chemical evolution models. We try to draw conclusions about the star formation history and the age of the last burst in IZw18.

scholarly journals STAR FORMATION HISTORY AND CHEMICAL EVOLUTION OF THE SEXTANS DWARF SPHEROIDAL GALAXY

2009 ◽  
Vol 703 (1) ◽  
pp. 692-701 ◽  
Author(s):  
Myung Gyoon Lee ◽  
In-Soo Yuk ◽  
Hong Soo Park ◽  
Jason Harris ◽  
Dennis Zaritsky
Keyword(s):  
Star Formation ◽  
Chemical Evolution ◽  
Star Formation History ◽  
Formation History

scholarly journals The LMC Centre Unfolding

1999 ◽  
Vol 190 ◽  
pp. 357-358 ◽  
Author(s):  
A. Ardeberg ◽  
P. Linde ◽  
B. Gustafsson
Keyword(s):  
Star Formation ◽  
Chemical Evolution ◽  
Star Formation History ◽  
Formation History

We study star formation history and chemical evolution in the LMC Bar centre. With the HST PC and WFC plus uvby photometry, we find 30% of the stars younger than 200 My and evidence for reduced star formation 3 to 0.2 Gy ago. The overall [Fe/H] is −0.5. Many stars older than 4 Gy contradict a very young Bar.

scholarly journals A Comparison of Chemical Evolution between the Milky Way and M31 Galaxy

2006 ◽  
Vol 2 (S235) ◽  
pp. 313-313
Author(s):  
J. Yin ◽  
J.L. Hou ◽  
R.X. Chang ◽  
S. Boissier ◽  
N. Prantzos
Keyword(s):  
Star Formation ◽  
Chemical Evolution ◽  
Milky Way ◽  
Local Group ◽  
Spiral Galaxies ◽  
Star Formation History ◽  
Milky Way Galaxy ◽  
Andromeda Galaxy ◽  
Formation History ◽  
Formation And Evolution

Andromeda galaxy (M31,NGC224) is the biggest spiral in the Local Group. By studying the star formation history(SFH) and chemical evolution of M31, and comparing with the Milky Way Galaxy, we are able to understand more about the formation and evolution of spiral galaxies.

scholarly journals SMART for the Next Decade

2009 ◽  
Vol 5 (S262) ◽  
pp. 291-294
Author(s):  
Myung Gyoon Lee ◽  
In-Soo Yuk ◽  
Sungsoon Lim
Keyword(s):  
Star Formation ◽  
Chemical Evolution ◽  
Star Formation History ◽  
Formation History

AbstractSMART is a model to derive both star formation history and chemical evolution simultaneously from color-magnitude diagrams of resolved stars in a galaxy. We present current progress and discuss the prospects of SMART for the next decade.

scholarly journals Stellar Populations and the Star Formation Histories of LSB Galaxies—Part I: Optical and HαImaging

2011 ◽  
Vol 2011 ◽  
pp. 1-18 ◽  
Author(s):  
James Schombert ◽  
Tamela Maciel ◽  
Stacy McGaugh
Keyword(s):  
Star Formation ◽  
Data Storage ◽  
Star Formation History ◽  
Star Forming ◽  
Reduction Techniques ◽  
Formation History ◽  
History Of ◽  
Star Formation Histories ◽  
Baryonic Mass ◽  
Lsb Galaxies

This paper presents optical and Hαimaging for a large sample of LSB galaxies selected from the PSS-II catalogs (Schombert et al., 1992). As noted in previous work, LSB galaxies span a range of luminosities () and sizes (), although they are consistent in their irregular morphology. Their Hαluminosities (L(Hα)) range from 1036to 1041 ergs s−1(corresponding to a range in star formation, using canonical prescriptions, from 10−5to 1  yr−1). Although their optical colors are at the extreme blue edge for galaxies, they are similar to the colors of dwarf galaxies (Van Zee, 2001) and gas-rich irregulars (Hunter and Elmegreen, 2006). However, their star formation rates per unit stellar mass are a factor of ten less than other galaxies of the same baryonic mass, indicating that they are not simply quiescent versions of more active star-forming galaxies. This paper presents the data, reduction techniques, and new philosophy of data storage and presentation. Later papers in this series will explore the stellar population and star formation history of LSB galaxies using this dataset.

scholarly journals BGM FASt: Besançon Galaxy Model for big data

2018 ◽  
Vol 620 ◽  
pp. A79 ◽  
Author(s):  
R. Mor ◽  
A. C. Robin ◽  
F. Figueras ◽  
T. Antoja
Keyword(s):  
Distribution Function ◽  
Star Formation ◽  
Mass Density ◽  
Mass Range ◽  
Star Formation History ◽  
Solar Neighbourhood ◽  
Parameter Inference ◽  
Formation History ◽  
Galaxy Model ◽  
Validation Tests

Aims. We develop a new theoretical framework to generate Besançon Galaxy Model Fast Approximate Simulations (BGM FASt) to address fundamental questions of the Galactic structure and evolution performing multi-parameter inference. As a first application of our strategy we simultaneously infer the initial-mass function (IMF), the star formation history and the stellar mass density in the solar neighbourhood. Methods. The BGM FASt strategy is based on a reweighing scheme, that uses a specific pre-sampled simulation, and on the assumption that the distribution function of the generated stars in the Galaxy can be described by an analytical expression. To evaluate the performance of our strategy we execute a set of validation tests. Finally, we use BGM FASt together with an approximate Bayesian computation algorithm to obtain the posterior probability distribution function of the inferred parameters, by automatically comparing synthetic versus Tycho-2 colour-magnitude diagrams. Results. The validation tests show a very good agreement between equivalent simulations performed with BGM FASt and the standard BGM code, with BGM FASt being ∼104 times faster. From the analysis of the Tycho-2 data we obtain a thin-disc star formation history decreasing in time and a present rate of 1.2 ± 0.2 M ⊙ yr−1. The resulting total stellar volume mass density in the solar neighbourhood is 0.051−0.005+0.002 M⊙ pc−3 and the local dark matter density is 0.012 ± 0.001 M ⊙ pc−3. For the composite IMF, we obtain a slope of α2 = 2.1−0.3+0.1 in the mass range between 0.5 M⊙ and 1.53 M⊙. The results of the slope at the high-mass range are trustable up to 4 M⊙ and highly dependent on the choice of extinction map (obtaining α3 = 2.9−0.2+0.2 and α3 = 3.7−0.2+0.2, respectively, for two different extinction maps). Systematic uncertainties coming from model assumptions are not included. Conclusions. The good performance of BGM FASt demonstrates that it is a very valuable tool to perform multi-parameter inference using Gaia data releases.

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