scholarly journals Observational constraints on the origin of the elements

2020 ◽  
Vol 635 ◽  
pp. A38 ◽  
Author(s):  
P. Eitner ◽  
M. Bergemann ◽  
C. J. Hansen ◽  
G. Cescutti ◽  
I. R. Seitenzahl ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Globular Clusters ◽  
Local Thermodynamic Equilibrium ◽  
Galactic Chemical Evolution ◽  
Galactic Disc ◽  
Milky Way Galaxy ◽  
Halo Stars ◽  
Type Ia ◽  
Low Metallicity ◽  
Different Sources

The abundance ratios of manganese to iron in late-type stars across a wide metallicity range place tight constraints on the astrophysical production sites of Fe-group elements. In this work, we investigate the chemical evolution of Mn in the Milky Way galaxy using high-resolution spectroscopic observations of stars in the Galactic disc and halo stars, as well as a sample of globular clusters. Our analysis shows that local thermodynamic equilibrium (LTE) leads to a strong imbalance in the ionisation equilibrium of Mn I and Mn II lines. Mn I produces systematically (up to 0.6 dex) lower abundances compared to the Mn II lines. Non-LTE (NLTE) radiative transfer satisfies the ionisation equilibrium across the entire metallicity range, of −3 ≲ [Fe/H] ≲ −1, leading to consistent abundances from both ionisation stages of the element. We compare the NLTE abundances with Galactic Chemical Evolution models computed using different sources of type Ia and type II supernova (SN Ia and SN II) yields. We find that a good fit to our observations can be obtained by assuming that a significant (∼75%) fraction of SNe Ia stem from a sub-Chandrasekhar (sub-Mch) channel. While this fraction is larger than that found in earlier studies (∼50%), we note that we still require ∼25% near-Mch SNe Ia to obtain solar [Mn/Fe] at [Fe/H] = 0. Our new data also suggest higher SN II Mn yields at low metallicity than typically assumed in the literature.

scholarly journals Carbon and oxygen in metal-poor halo stars

2019 ◽  
Vol 622 ◽  
pp. L4 ◽  
Author(s):  
A. M. Amarsi ◽  
P. E. Nissen ◽  
M. Asplund ◽  
K. Lind ◽  
P. S. Barklem
Keyword(s):  
Chemical Evolution ◽  
Thermodynamic Equilibrium ◽  
Local Thermodynamic Equilibrium ◽  
Galactic Chemical Evolution ◽  
Elemental Abundances ◽  
Halo Stars ◽  
Effective Temperatures ◽  
Population Iii Stars ◽  
Hydrodynamic Effects ◽  
First Time

Carbon and oxygen are key tracers of the Galactic chemical evolution; in particular, a reported upturn in [C/O] towards decreasing [O/H] in metal-poor halo stars could be a signature of nucleosynthesis by massive Population III stars. We reanalyse carbon, oxygen, and iron abundances in 39 metal-poor turn-off stars. For the first time, we take into account 3D hydrodynamic effects together with departures from local thermodynamic equilibrium (LTE) when determining both the stellar parameters and the elemental abundances, by deriving effective temperatures from 3D non-LTE Hβ profiles, surface gravities from Gaia parallaxes, iron abundances from 3D LTE Fe II equivalent widths, and carbon and oxygen abundances from 3D non-LTE C I and O I equivalent widths. We find that [C/Fe] stays flat with [Fe/H], whereas [O/Fe] increases linearly up to 0.75 dex with decreasing [Fe/H] down to −3.0 dex. Therefore [C/O] monotonically decreases towards decreasing [C/H], in contrast to previous findings, mainly because the non-LTE effects for O I at low [Fe/H] are weaker with our improved calculations.

scholarly journals The effects of different Type Ia SN yields on Milky Way chemical evolution

2021 ◽  
Vol 503 (3) ◽  
pp. 3216-3231
Author(s):  
Marco Palla
Keyword(s):  
Chemical Evolution ◽  
White Dwarf ◽  
Time Distribution ◽  
Milky Way ◽  
Massive Stars ◽  
Abundance Patterns ◽  
Type Ia ◽  
Low Metallicity ◽  
Explosion Mechanism ◽  
Chemical Evolution Model

ABSTRACT We study the effect of different Type Ia SN nucleosynthesis prescriptions on the Milky Way chemical evolution. To this aim, we run detailed one-infall and two-infall chemical evolution models, adopting a large compilation of yield sets corresponding to different white dwarf progenitors (near-Chandrasekar and sub-Chandrasekar) taken from the literature. We adopt a fixed delay time distribution function for Type Ia SNe, in order to avoid degeneracies in the analysis of the different nucleosynthesis channels. We also combine yields for different Type Ia SN progenitors in order to test the contribution to chemical evolution of different Type Ia SN channels. The results of the models are compared with recent LTE and NLTE observational data. We find that ‘classical’ W7 and WDD2 models produce Fe masses and [α/Fe] abundance patterns similar to more recent and physical near-Chandrasekar and sub-Chandrasekar models. For Fe-peak elements, we find that the results strongly depend either on the white dwarf explosion mechanism (deflagration-to-detonation, pure deflagration, double detonation) or on the initial white dwarf conditions (central density, explosion pattern). The comparison of chemical evolution model results with observations suggests that a combination of near-Chandrasekar and sub-Chandrasekar yields is necessary to reproduce the data of V, Cr, Mn and Ni, with different fractions depending on the adopted massive stars stellar yields. This comparison also suggests that NLTE and singly ionized abundances should be definitely preferred when dealing with most of Fe-peak elements at low metallicity.

scholarly journals A new formulation of the Type Ia supernova rate and its consequences on galactic chemical evolution

2006 ◽  
Vol 372 (1) ◽  
pp. 265-275 ◽  
Author(s):  
F. Matteucci ◽  
N. Panagia ◽  
A. Pipino ◽  
F. Mannucci ◽  
S. Recchi ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Galactic Chemical Evolution ◽  
Type Ia Supernova ◽  
Type Ia ◽  
New Formulation

scholarly journals The C/O ratio at low metallicity: constraints on early chemical evolution from observations of Galactic halo stars

2009 ◽  
Vol 500 (3) ◽  
pp. 1143-1155 ◽  
Author(s):  
D. Fabbian ◽  
P. E. Nissen ◽  
M. Asplund ◽  
M. Pettini ◽  
C. Akerman
Keyword(s):  
Chemical Evolution ◽  
Galactic Halo ◽  
Halo Stars ◽  
Low Metallicity

scholarly journals The effect of different type Ia supernova progenitors on Galactic chemical evolution

2009 ◽  
Vol 501 (2) ◽  
pp. 531-538 ◽  
Author(s):  
F. Matteucci ◽  
E. Spitoni ◽  
S. Recchi ◽  
R. Valiante
Keyword(s):  
Chemical Evolution ◽  
Galactic Chemical Evolution ◽  
Type Ia Supernova ◽  
Type Ia

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 Nucleosynthesis imprints from different Type Ia supernova explosion scenarios and implications for galactic chemical evolution

2020 ◽  
Vol 644 ◽  
pp. A118
Author(s):  
F. Lach ◽  
F. K. Röpke ◽  
I. R. Seitenzahl ◽  
B. Coté ◽  
S. Gronow ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
White Dwarfs ◽  
Supernova Explosion ◽  
Detailed Comparison ◽  
Galactic Chemical Evolution ◽  
Type Ia Supernova ◽  
Type Ia ◽  
Pure Helium ◽  
Ia Supernovae ◽  
Insight Into

We analyze the nucleosynthesis yields of various Type Ia supernova explosion simulations including pure detonations in sub-Chandrasekhar mass white dwarfs; double detonations and pure helium detonations of sub-Chandrasekhar mass white dwarfs with an accreted helium envelope; a violent merger model of two white dwarfs; and deflagrations and delayed detonations in Chandrasekhar mass white dwarfs. We focus on the iron peak elements Mn, Zn, and Cu. To this end, we also briefly review the different burning regimes and production sites of these elements, as well as the results of abundance measurements and several galactic chemical evolution studies. We find that super-solar values of [Mn/Fe] are not restricted to Chandrasekhar mass explosion models. Scenarios including a helium detonation can significantly contribute to the production of Mn, in particular the models proposed for calcium-rich transients. Although Type Ia supernovae are often not accounted for as production sites of Zn and Cu, our models involving helium shell detonations can produce these elements in super-solar ratios relative to Fe. Our results suggest a re-consideration of Type Ia supernova yields in galactic chemical evolution models. A detailed comparison with observations can provide new insight into the progenitor and explosion channels of these events.

scholarly journals Impact of Hypernova νp-process Nucleosynthesis on the Galactic Chemical Evolution of Mo and Ru

2022 ◽  
Vol 924 (1) ◽  
pp. 29
Author(s):  
Hirokazu Sasaki ◽  
Yuta Yamazaki ◽  
Toshitaka Kajino ◽  
Motohiko Kusakabe ◽  
Takehito Hayakawa ◽  
...  
Keyword(s):  
Theoretical Prediction ◽  
Observational Data ◽  
Chemical Evolution ◽  
Elemental Abundance ◽  
Core Collapse ◽  
Galactic Chemical Evolution ◽  
Main Contributor ◽  
Elemental Abundances ◽  
The Galaxy ◽  
Low Metallicity

Abstract We calculate the Galactic Chemical Evolution of Mo and Ru by taking into account the contribution from ν p-process nucleosynthesis. We estimate yields of p-nuclei such as 92,94Mo and 96,98Ru through the ν p-process in various supernova progenitors based upon recent models. In particular, the ν p-process in energetic hypernovae produces a large amount of p-nuclei compared to the yield in ordinary core-collapse SNe. Because of this, the abundances of 92,94Mo and 96,98Ru in the Galaxy are significantly enhanced at [Fe/H] = 0 by the ν p-process. We find that the ν p-process in hypernovae is the main contributor to the elemental abundance of 92Mo at low metallicity [Fe/H] < −2. Our theoretical prediction of the elemental abundances in metal-poor stars becomes more consistent with observational data when the ν p-process in hypernovae is taken into account.

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