scholarly journals The Galactic Thick Disk: An Observational Perspective

2009 ◽  
Vol 5 (S265) ◽  
pp. 289-299
Author(s):  
Bacham E. Reddy
Keyword(s):  
Galaxy Formation ◽  
Chemical Properties ◽  
Thick Disk ◽  
Elemental Abundance ◽  
Distinct Component ◽  
Chemical Enrichment ◽  
Abundance Patterns ◽  
The Galaxy ◽  
Star Formation Histories ◽  
And Chemical Properties

AbstractIn this review, we present a brief description of observational efforts to understand the Galactic thick disk and its relation to the other Galactic components. This review primarily focused on elemental abundance patterns of the thick disk population to understand the process or processes that were responsible for its existence and evolution. Kinematic and chemical properties of disk stars establish that the thick disk is a distinct component in the Milky Way, and its chemical enrichment and star formation histories hold clues to the bigger picture of understanding the Galaxy formation.

scholarly journals Globular Clusters and Field Halo Stars

1988 ◽  
Vol 126 ◽  
pp. 133-148
Author(s):  
Bruce W. Carney
Keyword(s):  
Distribution Function ◽  
Globular Clusters ◽  
Chemical Properties ◽  
Elemental Abundance ◽  
Stellar Kinematics ◽  
Halo Stars ◽  
Abundance Patterns ◽  
Halo Population ◽  
Metallicity Distribution ◽  
And Chemical Properties

Recent work on the chemistry and kinematics of the field halo population stars is reviewed, including the metallicity distribution function, elemental abundance patterns, primordial abundances, and their relations with stellar kinematics. The important role played by these stars in determining the ages of the globular clusters is discussed. A comparison is made between the kinematic and chemical properties of the field and cluster stars to ascertain if they share a common history.

Statistical criteria of stellar population types

1966 ◽  
Vol 24 ◽  
pp. 101-110
Author(s):  
W. Iwanowska
Keyword(s):  
Stellar Population ◽  
Chemical Properties ◽  
Spectrophotometric Study ◽  
Physical And Chemical Properties ◽  
Population Type ◽  
The Galaxy ◽  
Distribution Parameters ◽  
Physical And Chemical ◽  
Statistical Criteria ◽  
And Chemical Properties

In connection with the spectrophotometric study of population-type characteristics of various kinds of stars, a statistical analysis of kinematical and distribution parameters of the same stars is performed at the Toruń Observatory. This has a twofold purpose: first, to provide a practical guide in selecting stars for observing programmes, second, to contribute to the understanding of relations existing between the physical and chemical properties of stars and their kinematics and distribution in the Galaxy.

scholarly journals The chemical fingerprints of the thin and the thick disk

2008 ◽  
Vol 4 (S254) ◽  
pp. 197-202
Author(s):  
Sofia Feltzing ◽  
Sally Oey ◽  
Thomas Bensby
Keyword(s):  
Past History ◽  
Thick Disk ◽  
Chemical Abundance ◽  
Dwarf Stars ◽  
Abundance Patterns ◽  
The Galaxy ◽  
Thin And Thick Disks ◽  
Thick Disks ◽  
Definition Of ◽  
Galactic Stellar Populations

AbstractThe past history and origin of the different Galactic stellar populations are manifested in their different chemical abundance patterns. We obtained new elemental abundances for 553 F and G dwarf stars, to more accurately quantify these patterns for the thin and thick disks. However, the exact definition of disk membership is not straightforward. Stars that have a high likelihood of belonging to the thin disk show different abundance patterns from those for the thick disk. In contrast, we show that stars for the Hercules Stream do not show unique abundance patterns, but rather follow those of the thin and thick disks. This strongly suggests that the Hercules Stream is a feature induced by internal dynamics within the Galaxy rather than the remnant of an accreted satellite.

scholarly journals Chemical evolution of the Galaxy disk in connection with large-scale winds

2008 ◽  
Vol 4 (S254) ◽  
pp. 393-398
Author(s):  
Takuji Tsujimoto ◽  
Joss Bland-Hawthorn ◽  
Kenneth C. Freeman
Keyword(s):  
Chemical Evolution ◽  
Large Scale ◽  
Solar Neighborhood ◽  
Elemental Abundance ◽  
Abundance Gradient ◽  
Chemical Enrichment ◽  
Outer Disk ◽  
The Galaxy ◽  
Galaxy Disk ◽  
Set Up

AbstractComparison of elemental abundance features between old and young thin disk stars may reveal the action of ravaging winds from the Galactic bulge, which once enriched the whole disk, and set up the steep abundance gradient in the inner disk (RGC ≲ 10–;12 kpc) and simultaneously the metallicity floor ([Fe/H]~ −0.5) in the outer disk. After the end of a crucial influence by winds, chemical enrichment through accretion of a metal-poor material from the halo onto the disk gradually reduced the metallicity of the inner region, whereas an increase in the metallicity proceeded beyond a solar circle. This results in a flattening of abundance gradient in the inner disk, and our chemical evolution models confirm this mechanism for a flattening, which is in good agreement with the observations. Our scenario also naturally explains an observed break in the metallicity floor of the outer disk by young stars since the limit of self-enrichment in the outer disk is supposed to be [Fe/H]≲ −1 and inevitably incurs a direct influence of the dilution by a low-metal infall whose metallicity is [Fe/H]~ −1. Accordingly, we propose that the enrichment by large-scale winds is a crucial factor for chemical evolution of the disk, and claim to reconsider the models thus far for the disk including the solar neighborhood, in which the metallicity is predicted to monotonously increase with time. Furthermore, we anticipate that a flattening of abundance gradient together with a metal-rich floor in the outer disk are the hallmark of disk galaxies with significant central bulges.

scholarly journals Star Formation Histories of Dwarf Galaxies from the Colour-Magnitude Diagrams of Their Resolved Stellar Populations

2010 ◽  
Vol 2010 ◽  
pp. 1-25 ◽  
Author(s):  
Michele Cignoni ◽  
Monica Tosi
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Dwarf Galaxies ◽  
Early Type ◽  
Significant Difference ◽  
Magnitude Diagram ◽  
The Galaxy ◽  
Show Evidence ◽  
History Of ◽  
Star Formation Histories

In this tutorial paper we summarize how the star formation (SF) history of a galactic region can be derived from the colour-magnitude diagram (CMD) of its resolved stars. The procedures to build synthetic CMDs and to exploit them to derive the SF histories (SFHs) are described, as well as the corresponding uncertainties. The SFHs of resolved dwarf galaxies of all morphological types, obtained from the application of the synthetic CMD method, are reviewed and discussed. To summarize: (1) only early-type galaxies show evidence of long interruptions in the SF activity; late-type dwarfs present rather continuous, orgasping, SF regimes; (2) a few early-type dwarfs have experienced only one episode of SF activity concentrated at the earliest epochs, whilst many others show extended or recurrent SF activity; (3) no galaxy experiencing now its first SF episode has been found yet; (4) no frequent evidence of strong SF bursts is found; (5) there is no significant difference in the SFH of dwarf irregulars and blue compact dwarfs, except for the current SF rates. Implications of these results on the galaxy formation scenarios are briefly discussed.

scholarly journals MaNGA: Mapping Nearby Galaxies at Apache Point Observatory

2014 ◽  
Vol 10 (S311) ◽  
pp. 100-103
Author(s):  
Kevin Bundy
Keyword(s):  
Galaxy Formation ◽  
Signal To Noise Ratio ◽  
Data Set ◽  
Chemical Enrichment ◽  
Early Results ◽  
Galaxy Formation And Evolution ◽  
Nearby Galaxies ◽  
Formation And Evolution ◽  
Large Telescopes ◽  
Star Formation Histories

AbstractI describe a new integral field spectroscopic survey called MaNGA (Mapping Nearby Galaxies at Apache Point Observatory). One of three core programs in the 6-year SDSS-IV project† that began on July 1st, 2014, MaNGA will deploy 17 fiber-bundle IFUs across the Sloan 2.5m Telescope's 3 degree field-of-view, targeting a mass-selected sample with a median redshift of 0.03, typical spatial resolution of 1-2 kpc, and a per-fiber signal-to-noise ratio of 4-8 in the outskirts of target galaxies. For each galaxy in the sample, MaNGA will provide maps and measured gradients of the composition and dynamics of both stars and gas. I discuss early results that highlight MaNGA's potential to shed light on the ionization and chemical enrichment of gas in galaxies, spatial patterns in their star formation histories, and the internal makeup of stellar populations. MaNGA's unprecedented data set will not only provide powerful new insight on galaxy formation and evolution but will serve as a valuable benchmark for future high-z observations from large telescopes and space-based facilities.

scholarly journals The Transition from Disk to Halo as seen from Correlations between Kinematics and Metallicity

1995 ◽  
Vol 164 ◽  
pp. 391-391
Author(s):  
S. Bartašiūtė
Keyword(s):  
Chemical Properties ◽  
Galactic Latitude ◽  
Kinematic Parameters ◽  
High Galactic Latitude ◽  
Angular Momenta ◽  
The Galaxy ◽  
Color Data ◽  
The Relationship ◽  
Radial Velocity Data ◽  
And Chemical Properties

An investigation has been made to determine the relationship between kinematic and chemical properties of stars covering nearly all population types in the Galaxy. For this purpose, a sample has been taken of about 1150 high-galactic-latitude F–K stars down to V = 14.0, for which photoelectric seven-color data in the Vilnius medium-band system were collected at the Maidanak Observatory in Uzbekistan, Central Asia. Combining the obtained photometric material with the proper motion and radial velocity data enabled us to compute kinematic parameters of the sample stars and then to make plots of the galactic orbital eccentricities, angular momenta, and velocity dispersions versus [Fe/H], with much attention drawn to the region where the transition between the thin disk and halo occurs.

scholarly journals Galactic Chemical Evolution in the Context of the Recently Revealed SNe Ia Delay Time Distribution

2011 ◽  
Vol 7 (S281) ◽  
pp. 251-252
Author(s):  
Takuji Tsujimoto
Keyword(s):  
Chemical Evolution ◽  
Delay Time ◽  
Time Distribution ◽  
Chemical Properties ◽  
Thin Disk ◽  
Chemical Enrichment ◽  
Precise Knowledge ◽  
The Galaxy ◽  
Type Ia ◽  
Ia Supernovae

AbstractThe Galaxy is composed of four distinct structures, i.e., halo, bulge, and thick and thin disks, that are formed and evolved on different timescales; thus accordingly the speeds of chemical enrichment are different from one another, which is imprinted in individual stellar abundances. To decipher them, precise knowledge of the timing of the release of nucleosynthesis materials from various production sites is critical. The delay time distribution (DTD) of Type Ia supernovae (SNe Ia), recently revealed by the SNe Ia surveys of external galaxies, is incorporated into the models of chemical evolution for each structure. Here we report that the observed chemical properties for the thin and thick disks are compatible with a new SNe Ia DTD, and suggests a close chemical connection between the two in the way that the thin disk is formed from gas left after thick disk formation. This nicely explains the lack of thin disk stars with [Fe/H] ≲ −0.8. In this new context, a top-heavy IMF for the bulge is firmly confirmed. Finally we discuss the possibility of some modification of the DTD that might be considered for the halo case.

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