The Halo Stars in NGC 5128. III. An Inner Halo Field and the Metallicity Distribution

2002 ◽  
Vol 123 (6) ◽  
pp. 3108-3123 ◽  
Author(s):  
William E. Harris ◽  
Gretchen L. H. Harris
Keyword(s):  
Halo Stars ◽  
Metallicity Distribution

The Metallicity Distribution in the Halo Stars of NGC 5128: Implications for Galaxy Formation

1999 ◽  
Vol 117 (2) ◽  
pp. 855-867 ◽  
Author(s):  
Gretchen L. H. Harris ◽  
William E. Harris ◽  
Gregory B. Poole
Keyword(s):  
Galaxy Formation ◽  
Halo Stars ◽  
Metallicity Distribution

scholarly journals EMP stars with high mass IMF and hierarchical galaxy formation

2009 ◽  
Vol 5 (S265) ◽  
pp. 128-129
Author(s):  
Yutaka Komiya ◽  
Takuma Suda ◽  
Asao Habe ◽  
Masayuki Y. Fujimoto
Keyword(s):  
Chemical Evolution ◽  
Galaxy Formation ◽  
Galactic Halo ◽  
Early Stage ◽  
Mass Function ◽  
Initial Mass Function ◽  
High Mass ◽  
Halo Stars ◽  
The Galaxy ◽  
Metallicity Distribution

AbstractExtremely metal-poor (EMP) stars in the Galactic halo are stars formed in the very early stage of the chemical evolution of the Galaxy. In previous study, we proposed that typical mass of EMP stars are massive, based on observations of carbon-enhanced EMP stars. In this study, we build a merger tree of the Galaxy semi-analytically and follow the chemical evolution along the merger tree. We also consider the effect of binary and high-mass initial mass function(IMF). Resultant theoretical metallicity distribution function (MDF) and abundance distribution are compared with observed metal-poor halo stars.

scholarly journals Extremely metal-poor stars in dwarf galaxies

2009 ◽  
Vol 5 (S265) ◽  
pp. 237-240
Author(s):  
Anna Frebel ◽  
Joshua D. Simon ◽  
Evan Kirby ◽  
Marla Geha ◽  
Beth Willman
Keyword(s):  
Galaxy Formation ◽  
Milky Way ◽  
Dwarf Galaxies ◽  
Formation Model ◽  
Abundance Pattern ◽  
Halo Stars ◽  
Abundance Patterns ◽  
Upper Limits ◽  
Stellar Halo ◽  
Metallicity Distribution

AbstractWe present Keck/HIRES spectra of six metal-poor stars in two of the ultra-faint dwarf galaxies orbiting the Milky Way, Ursa Major II and Coma Berenices, and a Magellan/MIKE spectrum of a star in the classical dwarf spheroidal galaxy (dSph) Sculptor. Our data include the first high-resolution spectroscopic observations of extremely metal-poor stars ([Fe/H] < −3.0) not belonging to the Milky Way (MW) stellar halo field population. We obtain abundance measurements and upper limits for up to 26 elements between carbon and europium. The stars span a range of −3.8 < [Fe/H] < −2.3, with the ultra-faints having large spreads in Fe. A comparison with MW halo stars of similar metallicity reveals substantial agreement between the abundance patterns of the ultra-faint dwarf galaxies and Sculptor and the MW halo for the light, α and iron-peak elements (C to Zn). This agreement contrasts with the results of earlier studies of more metal-rich stars (−2.5 ≲[Fe/H]≲ −1.0) in more luminous dwarfs, which found significant abundance discrepancies with respect to the MW halo data. The abundances of neutron-capture elements (Sr to Eu) in all three galaxies are extremely low, consistent with the most metal-poor halo stars, but not with the typical halo abundance pattern at [Fe/H]≳ −3.0. Our results are broadly consistent with a galaxy formation model which predicts that massive dwarf galaxies are the source of the metal-rich component ([Fe/H]≳ −2.5) of the MW inner halo, but we propose that dwarf galaxies similar to the dSphs are the primary contributors to the metal-poor end of the metallicity distribution of the MW outer halo.

scholarly journals The difference in metallicity distribution functions of halo stars and globular clusters as a function of galaxy type

2017 ◽  
Vol 606 ◽  
pp. A85 ◽  
Author(s):  
H. J. G. L. M. Lamers ◽  
J. M. D. Kruijssen ◽  
N. Bastian ◽  
M. Rejkuba ◽  
M. Hilker ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Distribution Functions ◽  
Halo Stars ◽  
Galaxy Type ◽  
The Difference ◽  
Metallicity Distribution

The Halo Stars in NGC 5128. II. An Outer Halo Field and a New Metallicity Distribution

2000 ◽  
Vol 120 (5) ◽  
pp. 2423-2436 ◽  
Author(s):  
Gretchen L. H. Harris ◽  
William E. Harris
Keyword(s):  
Halo Stars ◽  
Metallicity Distribution

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.

scholarly journals Photometric Metallicity of the Sagittarius Stream in the south Galactic cap

2015 ◽  
Vol 11 (S317) ◽  
pp. 294-295
Author(s):  
Cuihua Du ◽  
Jiayin Gu ◽  
Yunpeng Jia ◽  
Xiyan Peng ◽  
Zhenyu Wu ◽  
...  
Keyword(s):  
Distribution Function ◽  
Gaussian Model ◽  
Mixed Population ◽  
The South ◽  
Halo Stars ◽  
Sky Survey ◽  
Metallicity Distribution

AbstractBased on SDSS and South Galactic Cap U-band Sky Survey (SCUSS) photometry, we try to study the photometric metallicity of the Sagittarius (Sgr) stream in the south Galactic cap. We find that the Sgr stream has a wider metallicity distribution, and that its median metallicity is richer than that of the field halo stars. The neighboring field halo stars in our studied fields can be modeled by a two-Gaussian model, with peaks at [Fe/H]= −1.9 and [Fe/H]= −1.5. The metallicity distribution function (MDF) of the mixed population (Sgr stream and halo stars) has peaks at [Fe/H]= −1.9, [Fe/H]= −1.5 and [Fe/H]= −0.5, respectively.

scholarly journals Metallicity Distribution and Kinematics of the Disk and Halo F-G Stars

1995 ◽  
Vol 164 ◽  
pp. 387-387
Author(s):  
Ilfan F. Bikmaev
Keyword(s):  
Large Magellanic Cloud ◽  
Thick Disk ◽  
Disk Formation ◽  
Halo Stars ◽  
The Galaxy ◽  
Iron Abundance ◽  
Long Time ◽  
Galaxy Populations ◽  
Abundance Determination ◽  
Metallicity Distribution

The iron abundance of 160 disk and halo F-G-dwarfs is determined from 6-m spectra of 60 stars and published equivalent width data. Kurucz's (1979) model atmospheres and WIDTH6 programme are used for iron abundance determination. We have shown that FeI lines are formed under non-LTE conditions (Bikmaev et al.,1990), and so used Fell lines for iron abundance determination, following Bikmaev (1991). The use of the FeII lines and high quality homogeneous spectroscopic data decreases systematic and accidental errors and allows us to obtain qualitatively new results (Bikmaev, 1994). The distribution of the sample of stars is a non-monotonous function of metallicity: at least 3 groups of stars are seen, corresponding to the three Galaxy populations - disk ([Fe/H]=+0.1 to −0.3), thick disk ([Fe/H]=−0.7 to −0.8) and halo ([Fe/H]=−1.3 to −2.0). In contrast with previous studies, a sharp boundary in the kinematic characteristics (the eccentricity of space orbits and angular velocity) was found at [Fe/H]=−0.9, the boundary between disk and halo stars. These kinematic properties demand a relatively long time between halo and disk formation. The average metallicity of the thick disk stars is very close to the metallicity of the Large Magellanic Cloud. Perhaps an explanation is merging during the approach of the LMC to the Galaxy several billion years ago.

scholarly journals The dynamically selected stellar halo of the Galaxy with Gaia and the tilt of the velocity ellipsoid

2018 ◽  
Vol 615 ◽  
pp. A70 ◽  
Author(s):  
Lorenzo Posti ◽  
Amina Helmi ◽  
Jovan Veljanoski ◽  
Maarten A. Breddels
Keyword(s):  
Gravitational Potential ◽  
Selection Criteria ◽  
Solar Neighbourhood ◽  
Local Velocity ◽  
Halo Stars ◽  
The Galaxy ◽  
Stellar Halo ◽  
Dynamical Properties ◽  
Metallicity Distribution ◽  
Dynamical Criterion

Aims. We study the dynamical properties of halo stars located in the solar neighbourhood. Our goal is to explore how the properties of the halo depend on the selection criteria used to define a sample of halo stars. Once this is understood, we proceed to measure the shape and orientation of the halo’s velocity ellipsoid and we use this information to put constraints on the gravitational potential of the Galaxy. Methods. We use the recently released Gaia DR1 catalogue cross-matched to the RAVE dataset for our analysis. We develop a dynamical criterion based on the distribution function of stars in various Galactic components, using action integrals to identify halo members, and we compare this to the metallicity and to kinematically selected samples. Results. With this new method, we find 1156 stars in the solar neighbourhood that are likely members of the stellar halo. Our dynamically selected sample consists mainly of distant giants on elongated orbits. Their metallicity distribution is rather broad, with roughly half of the stars having [M/H] ≥ −1 dex. The use of different selection criteria has an important impact on the characteristics of the velocity distributions obtained. Nonetheless, for our dynamically selected and for the metallicity selected samples, we find the local velocity ellipsoid to be aligned in spherical coordinates in a Galactocentric reference frame. This suggests that the total gravitational potential is rather spherical in the region spanned by the orbits of the halo stars in these samples.

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