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 Testing galaxy formation simulations with damped Lyman-α abundance and metallicity evolution

2020 ◽  
Vol 492 (2) ◽  
pp. 2835-2846 ◽  
Author(s):  
Sultan Hassan ◽  
Kristian Finlator ◽  
Romeel Davé ◽  
Christopher W Churchill ◽  
J Xavier Prochaska
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Star Formation Rate ◽  
Initial Conditions ◽  
Mass Density ◽  
Formation Rate ◽  
Thomson Scattering ◽  
Stellar Mass ◽  
Rate Functions ◽  
Metallicity Distribution

ABSTRACT We examine the properties of damped Lyman-α absorbers (DLAs) emerging from a single set of cosmological initial conditions in two state-of-the-art cosmological hydrodynamic simulations: simba and technicolor dawn. The former includes star formation and black hole feedback treatments that yield a good match with low-redshift galaxy properties, while the latter uses multifrequency radiative transfer to model an inhomogeneous ultraviolet background (UVB) self-consistently and is calibrated to match the Thomson scattering optical depth, UVB amplitude, and Ly α forest mean transmission at z &gt; 5. Both simulations are in reasonable agreement with the measured stellar mass and star formation rate functions at z ≥ 3, and both reproduce the observed neutral hydrogen cosmological mass density, $\Omega _{\rm H\, \small{I}}(z)$. However, the DLA abundance and metallicity distribution are sensitive to the galactic outflows’ feedback and the UVB amplitude. Adopting a strong UVB and/or slow outflows underproduces the observed DLA abundance, but yields broad agreement with the observed DLA metallicity distribution. By contrast, faster outflows eject metals to larger distances, yielding more metal-rich DLAs whose observational selection may be more sensitive to dust bias. The DLA metallicity distribution in models adopting an H2-regulated star formation recipe includes a tail extending to [M/H] ≪ −3, lower than any DLA observed to date, owing to curtailed star formation in low-metallicity galaxies. Our results show that DLA observations play an important role in constraining key physical ingredients in galaxy formation models, complementing traditional ensemble statistics such as the stellar mass and star formation rate functions.

scholarly journals On the chemical evolution of the Milky Way

2008 ◽  
Vol 4 (S254) ◽  
pp. 381-392 ◽  
Author(s):  
Nikos Prantzos
Keyword(s):  
Chemical Evolution ◽  
Galaxy Formation ◽  
Milky Way ◽  
Chemical Properties ◽  
Solar Neighborhood ◽  
Satellite Galaxies ◽  
Metallicity Distribution

AbstractI discuss three different topics concerning the chemical evolution of the Milky Way (MW). 1) The metallicity distribution of the MW halo; it is shown that this distribution can be analytically derived in the framework of the hierarchical merging scenario for galaxy formation, assuming that the component sub-haloes had chemical properties similar to those of the progenitors of satellite galaxies of the MW. 2) The age-metallicity relationship (AMR) in the solar neighborhood; I argue for caution in deriving from data with important uncertainties (such as the age uncertainties in the Geneva-Copenhagen Survey) a relationship between average metallicity and age: derived relationships are shown to be systematically flatter than the true ones and should not be directly compared to models. 3) The radial mixing of stars in the disk, which may have important effects on various observables (scatter in AMR, extension of the tails of the metallicity distribution, flatenning of disk abundance profiles). Recent SPH + N-body simulations find considerable radial mixing, but only comparison to observations will ultimately determine the extent of that mixing.

scholarly journals Chemical Evolution of R-process Elements in the Hierarchical Galaxy Formation

2015 ◽  
Vol 11 (S317) ◽  
pp. 318-319
Author(s):  
Yutaka Komiya ◽  
Toshikazu Shigeyama
Keyword(s):  
Neutron Star ◽  
Chemical Evolution ◽  
Galaxy Formation ◽  
Milky Way ◽  
Galactic Chemical Evolution ◽  
Halo Stars ◽  
R Process ◽  
Process Elements ◽  
Milky Way Halo

AbstractThe main astronomical source of r-process elements has not yet been identified. One plausible site is neutron star mergers (NSMs). From the perspective of Galactic chemical evolution, however, it has been pointed out that the NSM scenario is incompatible with observations. Recently, Tsujimoto & Shigeyama (2014) pointed out that NSM ejecta can spread into much larger volume than ejecta from a supernova. We re-examine the chemical evolution of r-process elements under the NSM scenario considering this difference in propagation of the ejecta. We find that the NSM scenario can be compatible with the observed abundances of the Milky Way halo stars.

scholarly journals Building Blocks of the Milky Way's Stellar Halo

2015 ◽  
Vol 11 (S317) ◽  
pp. 373-374
Author(s):  
Pim van Oirschot ◽  
Else Starkenburg ◽  
Amina Helmi ◽  
Gijs Nelemans
Keyword(s):  
Galaxy Formation ◽  
Stellar Population ◽  
Milky Way ◽  
Building Blocks ◽  
Formation Model ◽  
Halo Stars ◽  
Stellar Halo ◽  
History Of ◽  
Dynamical Properties ◽  
Star Formation Histories

AbstractWe study the assembly history of the stellar halo of Milky Way-like galaxies using the six high-resolution Aquarius dark matter simulations combined with the Munich-Groningen semi-analytic galaxy formation model. Our goal is to understand the stellar population contents of the building blocks of the Milky Way halo, including their star formation histories and chemical evolution, as well as their internal dynamical properties. We are also interested in how they relate or are different from the surviving satellite population. Finally, we will use our models to compare to observations of halo stars in an attempt to reconstruct the assembly history of the Milky Way's stellar halo itself.

scholarly journals The Globular Cluster Systems in the Coma Ellipticals. II. Metallicity Distribution and Radial Structure in NGC 4874 and Implications for Galaxy Formation

2000 ◽  
Vol 533 (1) ◽  
pp. 137-148 ◽  
Author(s):  
William E. Harris ◽  
J. J. Kavelaars ◽  
David A. Hanes ◽  
James E. Hesser ◽  
Christopher J. Pritchet
Keyword(s):  
Galaxy Formation ◽  
Globular Cluster ◽  
Cluster Systems ◽  
Radial Structure ◽  
Metallicity Distribution

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

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

scholarly journals Star Formation and Chemical Evolution of Damped Ly-α Systems

2001 ◽  
Vol 204 ◽  
pp. 417-417
Author(s):  
Jun Ma
Keyword(s):  
Star Formation ◽  
Chemical Evolution ◽  
Galaxy Formation ◽  
Gravitational Instability ◽  
Rotational Velocity ◽  
Mean Value ◽  
Box Model ◽  
Dark Matter Halo ◽  
Circular Velocity ◽  
Metallicity Distribution

In this paper, we investigate the star formation and chemical evolution of damped Lyman-α systems (DLAs) based on the disk galaxy formation model developed by H. J. Mo, S. Mao, & S. D. M. White (1998, MNRAS, 295, 319). We propose that the DLAs are the central galaxies of less massive dark haloes present at redshifts z ~ 3, and that they should inhabit haloes of moderately low circular velocity. We adopt the empirical Schmidt law of star formation rates, and a closed box model of chemical evolution in which an approximation known as instantaneous recycling is assumed. In calculating the predicted distribution of metallicities for DLAs in our models, two cases are considered. One is that, using the closed box model, empirical Schmidt law, and star formation epoch, the distribution of metallicity can be directly calculated. The other is that, when the simple gravitational instability of a thin isothermal gas disk first discussed by A. Toomre (1964, ApJ, 139, 1217) is considered, star formation occurs only in the region where the surface density of gas satisfies the critical value — rather than everywhere in the gas disk. We first obtain the region where star formation can occur by assuming that the disk has a flat rotation curve and that the rotational velocity is equal to the circular velocity of the surrounding dark matter halo. We then calculate the metallicity distribution for case one. We assume that star formation in each DLA lasts for a period of 1 Gyr from redshifts z = 3. There is only one output parameter in our model, i.e., the stellar yield, which relates to the epoch of star formation. It is obtained by normalizing the predicted distribution of metallicity to the mean value of 1/13 Z⊙ as presented by M. Pettini, L. J. Smith, D. L. Kind, & R. W. Hunstead (1997, ApJ, 486, 665). The predicted metallicity distribution is consistent with current (rather limited) observational data. A random distribution of galactic disks is taken into account.

Sign in / Sign up

Export Citation Format

Share Document