scholarly journals The abundance distribution of [α/Fe] in the Galactic disk stars

2013 ◽  
Vol 9 (S298) ◽  
pp. 419-420
Author(s):  
Ji Li ◽  
Ruijuan Fu
Keyword(s):  
Statistical Analysis ◽  
Star Formation ◽  
Chemical Evolution ◽  
Galactic Disk ◽  
Abundance Ratio ◽  
Thick Disk ◽  
Abundance Distribution ◽  
Dwarf Stars ◽  
The Galaxy ◽  
History Of

AbstractThe abundance ratio [α/Fe] is a useful tracer to probe the history of star formation and the chemical evolution of the Galaxy. We present a statistical analysis of [α/Fe] in 953 dwarf stars to investigate the distributions of [α/Fe] in the the thin- and thick-disk stars.

scholarly journals Beryllium abundances and the formation of the halo and the thick disk

2009 ◽  
Vol 5 (S268) ◽  
pp. 483-488
Author(s):  
Rodolfo Smiljanic ◽  
L. Pasquini ◽  
P. Bonifacio ◽  
D. Galli ◽  
B. Barbuy ◽  
...  
Keyword(s):  
Star Formation ◽  
Formation Rate ◽  
Cosmic Ray ◽  
Thick Disk ◽  
Star Formation History ◽  
Halo Stars ◽  
Formation History ◽  
The Galaxy ◽  
History Of ◽  
Early Galaxy

AbstractThe single stable isotope of beryllium is a pure product of cosmic-ray spallation in the ISM. Assuming that the cosmic-rays are globally transported across the Galaxy, the beryllium production should be a widespread process and its abundance should be roughly homogeneous in the early-Galaxy at a given time. Thus, it could be useful as a tracer of time. In an investigation of the use of Be as a cosmochronometer and of its evolution in the Galaxy, we found evidence that in a log(Be/H) vs. [α/Fe] diagram the halo stars separate into two components. One is consistent with predictions of evolutionary models while the other is chemically indistinguishable from the thick-disk stars. This is interpreted as a difference in the star formation history of the two components and suggests that the local halo is not a single uniform population where a clear age-metallicity relation can be defined. We also found evidence that the star formation rate was lower in the outer regions of the thick disk, pointing towards an inside-out formation.

scholarly journals Two distinct halo populations in the solar neighborhood: evidence from stellar abundance of beryllium

2013 ◽  
Vol 9 (S298) ◽  
pp. 83-85
Author(s):  
Kefeng Tan ◽  
Gang Zhao
Keyword(s):  
Star Formation ◽  
Galactic Halo ◽  
Formation Rate ◽  
Solar Neighborhood ◽  
Elemental Abundance ◽  
Star Formation History ◽  
Dwarf Stars ◽  
Formation History ◽  
The Galaxy ◽  
History Of

AbstractIt is now generally believed that the Galaxy was formed through hierarchical merging, which means that different components of the Galaxy may have experienced different chemical evolution histories. Since alpha elements are mainly produced by core collapse supernovae, they are closely associated with the star formation history of the Galaxy. In this regard, Galactic components with different alpha elemental abundance patterns may show different behaviors in beryllium abundances since the production of beryllium is correlated with the cosmic rays and thus the supernovae. A recent study by Nissen & Schuster (2010) has revealed the existence of two distinct halo populations in the solar neighborhood based on the alpha elemental abundances and kinematics of 94 dwarf stars. We determined beryllium abundances for some of these stars and find systematic differences in beryllium abundances between these two halo populations. Our results consolidate the conclusion of two distinct halo populations in the solar neighborhood. Our results also show that beryllium abundance is a very good indicator of star formation rate, and could be used to trace the substructures of the Galactic halo.

scholarly journals The Chemical Evolution of the Galactic Halo and Disk

1987 ◽  
Vol 115 ◽  
pp. 701-703
Author(s):  
Federico Ferrini ◽  
Francesco Palla ◽  
Steven N. Shore
Keyword(s):  
Star Formation ◽  
Chemical Evolution ◽  
Galactic Halo ◽  
Stellar Populations ◽  
Galactic Evolution ◽  
Formation Model ◽  
Present Epoch ◽  
The Galaxy ◽  
Metal Abundance ◽  
History Of

The history of star formation in our galaxy is written in the metal abundance distributions of the stellar populations. Any star formation model is constrained by two facts. First, there was a period in the early stages of galactic evolution during which the metallicity of the gas out of which stars were being formed was significantly lower than the present epoch. Second, there is a paucity of extremely metal deficient stars in the disk of the galaxy.

scholarly journals The Gaia-ESO Survey: The N/O abundance ratio in the Milky Way

2018 ◽  
Vol 618 ◽  
pp. A102 ◽  
Author(s):  
L. Magrini ◽  
F. Vincenzo ◽  
S. Randich ◽  
E. Pancino ◽  
G. Casali ◽  
...  
Keyword(s):  
Star Formation ◽  
Chemical Evolution ◽  
Milky Way ◽  
Open Cluster ◽  
Abundance Ratio ◽  
Open Clusters ◽  
Spatially Resolved ◽  
Wide Range ◽  
The Galaxy ◽  
Formation Efficiency

Context. The abundance ratio N/O is a useful tool to study the interplay of galactic processes, for example star formation efficiency, timescale of infall, and outflow loading factor. Aims. We aim to trace log(N/O) versus [Fe/H] in the Milky Way and to compare this ratio with a set of chemical evolution models to understand the role of infall, outflow, and star formation efficiency in the building up of the Galactic disc. Methods. We used the abundances from IDR2-3, IDR4, IDR5 data releases of the Gaia-ESO Survey both for Galactic field and open cluster stars. We determined membership and average composition of open clusters and we separated thin and thick disc field stars. We considered the effect of mixing in the abundance of N in giant stars. We computed a grid of chemical evolution models, suited to reproduce the main features of our Galaxy, exploring the effects of the star formation efficiency, infall timescale, and differential outflow. Results. With our samples, we map the metallicity range −0.6 ≤ [Fe/H] ≤ 0.3 with a corresponding −1.2 ≤ log(N/O) ≤ −0.2, where the secondary production of N dominates. Thanks to the wide range of Galactocentric distances covered by our samples, we can distinguish the behaviour of log(N/O) in different parts of the Galaxy. Conclusions. Our spatially resolved results allow us to distinguish differences in the evolution of N/O with Galactocentric radius. Comparing the data with our models, we can characterise the radial regions of our Galaxy. A shorter infall timescale is needed in the inner regions, while the outer regions need a longer infall timescale, coupled with a higher star formation efficiency. We compare our results with nebular abundances obtained in MaNGA galaxies, finding in our Galaxy a much wider range of log(N/O) than in integrated observations of external galaxies of similar stellar mass, but similar to the ranges found in studies of individual H II regions.

scholarly journals Kinematics and Dynamics of the Magellanic Clouds

1984 ◽  
Vol 108 ◽  
pp. 107-114
Author(s):  
K. C. Freeman
Keyword(s):  
Star Formation ◽  
Chemical Evolution ◽  
Magellanic Clouds ◽  
Star Formation History ◽  
Kinematics And Dynamics ◽  
List Type ◽  
Formation History ◽  
The Galaxy ◽  
History Of ◽  
Magellanic Stream

Why are the kinematics and dynamics of the Magellanic Clouds worth studying ? Some of the reasons are: 1.The Clouds are the closest examples of Magellanic systems. These asymmetric systems give some interesting dynamical problems. Because the Clouds are so close, a unique amount of information can be obtained on the kinematics of objects of all ages. This should be very helpful for understanding the dynamics.2.The Clouds and the Galaxy are interacting. This produces complex kinematics of the gas in and between the Clouds, and also the Magellanic Stream. Again, very detailed information can be derived. We would like to know enough about the gas dynamics of interacting galaxies, to be able to explain the kinematics produced by this interaction.3.The interaction will affect the star formation and chemical evolution in the Clouds. As new results are obtained on the star formation history and the chemical evolution, it is important to follow in parallel the dynamical history of the system, to see if the dynamics, star formation and chemical evolution can be tied together.

scholarly journals Planetary Nebulae and the Chemical Evolution of Galaxies

1983 ◽  
Vol 103 ◽  
pp. 463-472 ◽  
Author(s):  
Alfonso Serrano
Keyword(s):  
Star Formation ◽  
Chemical Evolution ◽  
Planetary Nebulae ◽  
Low Mass Stars ◽  
Chemical Enrichment ◽  
The Past ◽  
The Galaxy ◽  
History Of ◽  
Low Mass

Tinsley (1978) has done an excellent review that illustrates the methods and concepts that can be developed to assess the effects of planetary nebulae (PN) on the long-term history of the galaxy. Tinsley concluded that research in PN could put constraints on the past rate of star formation and provide information on chemical enrichment by low mass stars.

scholarly journals Bimodal chemical evolution of the Galactic disk and the Barium abundance of Cepheids

2013 ◽  
Vol 9 (S298) ◽  
pp. 86-91 ◽  
Author(s):  
Jacques R.D. Lépine ◽  
Sergei Andrievky ◽  
Douglas A. Barros ◽  
Thiago C. Junqueira ◽  
Sergio Scarano
Keyword(s):  
Chemical Evolution ◽  
Star Formation Rate ◽  
Galactic Disk ◽  
Formation Rate ◽  
Abundance Distribution ◽  
The Galaxy ◽  
Low Metallicity ◽  
The Difference ◽  
Two Sides ◽  
High Metallicity

AbstractIn order to understand the Barium abundance distribution in the Galactic disk based on Cepheids, one must first be aware of important effects of the corotation resonance, situated a little beyond the solar orbit. The thin disk of the Galaxy is divided in two regions that are separated by a barrier situated at that radius. Since the gas cannot get across that barrier, the chemical evolution is independent on the two sides of it. The barrier is caused by the opposite directions of flows of gas, on the two sides, in addition to a Cassini-like ring void of HI (caused itself by the flows). A step in the metallicity gradient developed at corotation, due to the difference in the average star formation rate on the two sides, and to this lack of communication between them. In connection with this, a proof that the spiral arms of our Galaxy are long-lived (a few billion years) is the existence of this step. When one studies the abundance gradients by means of stars which span a range of ages, like the Cepheids, one has to take into account that stars, contrary to the gas, have the possibility of crossing the corotation barrier. A few stars born on the high metallicity side are seen on the low metallicity one, and vice-versa. In the present work we re-discuss the data on Barium abundance in Cepheids as a function of Galactic radius, taking into account the scenario described above. The [Ba/H] ratio, plotted as a function of Galactic radius, apparently presents a distribution with two branches in the external region (beyond corotation). One can re-interpret the data and attribute the upper branch to the stars that were born on the high metallicity side. The lower branch, analyzed separately, indicates that the stars born beyond corotation have a rising Barium metallicity as a function of Galactic radius.

scholarly journals Identification of Cool White Dwarfs in the Sloan Digital Sky Survey

2000 ◽  
Vol 176 ◽  
pp. 514-514 ◽  
Author(s):  
T. S. Metcalfe ◽  
A. Mukadam ◽  
D. E. Winget ◽  
X. Fan ◽  
M. A. Strauss ◽  
...  
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Luminosity Function ◽  
Galactic Disk ◽  
Sloan Digital Sky Survey ◽  
Dwarf Stars ◽  
White Dwarf Stars ◽  
The Galaxy ◽  
History Of ◽  
Cool White Dwarfs

AbstractWe are searching for the coolest white dwarf stars in the galactic disk and halo. The Sloan survey, in due course, will identify an enormous number of new white dwarf stars which will better define the white dwarf luminosity function—an important tool for understanding the age and history of the stellar population of the galaxy. The broadband filter data obtained in the digital photometry phase of the survey will not permit identification of the most interesting of these, the coolest white dwarf stars. This is because the cool main sequence and subdwarf stars become indistinguishable from the white dwarfs in the various colorcolor diagrams. We have interference filters designed to separate out these classes of objects. We have obtained photometry of test fields to complement the Sloan data and identify the population of cool white dwarf stars. These data will ultimately resolve the controversies, based for the most part on small-number statistics, of the location of the turndown in the white dwarf luminosity function for the disk. If the halo is significantly older than the disk, we will find a second peak in the white dwarf luminosity function, at lower luminosities than the disk turndown. Our data will provide the first meaningful constraints on the location of the turndown in the halo white dwarf luminosity function.

scholarly journals Chemical and Dynamical History of the Milky Way

1996 ◽  
Vol 169 ◽  
pp. 389-394
Author(s):  
I.F. Bikmaev ◽  
L.I. Mashonkina ◽  
N.A. Sakhibullin ◽  
V.V. Shimanskij ◽  
N. Shimanskaya
Keyword(s):  
Star Formation ◽  
Chemical Element ◽  
Milky Way ◽  
Theoretical Models ◽  
High Quality ◽  
Dwarf Stars ◽  
Element Abundances ◽  
The Galaxy ◽  
History Of ◽  
Abundance Determination

F-G dwarf stars of different metallicity are used as tracers of chemical and dynamical history of the Galaxy. Observed ratios of element abundances “[X/Fe] versus [Fe/H]” (where “X” is a some of chemical element) are compared with theoretical ones and allow us to make the choice between models (or parameters of theoretical models) of the Galaxy chemical evolution, nucleosynthesis and processes of star formation. Our experience has shown (Bikmaev, 1991, 1994a,b; Bikmaev et al., 1990) that in some cases classical approaches in abundance determination are affected by methodical uncertainties and the spread in [X/Fe] ratios may be large even if high quality spectra used.

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