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.

scholarly journals Evidence of outflow from the Galactic bulge imprinted in stellar elemental abundances

2007 ◽  
Vol 3 (S245) ◽  
pp. 369-370
Author(s):  
Takuji Tsujimoto
Keyword(s):  
Black Hole ◽  
Galactic Halo ◽  
Elemental Abundance ◽  
Stellar Disk ◽  
Galactic Bulge ◽  
Interstellar Gas ◽  
Elemental Abundances ◽  
The Galaxy ◽  
Low Metallicity ◽  
Halo Gas

AbstractWe explore the elemental abundance features of metal-rich disk stars, highlighting the comparisons made with those of the recently revealed Galactic bulge stars. A similarity between two of the comparisons leads to a new theoretical picture of the bulge-disk connection in the Galaxy, where a supermassive black hole resides at the center. We postulate that a metal-rich outflow, triggered by feedback from a black hole, was generated and quenched the star formation, which had lasted several billion years in the bulge. The expelled gas cooled down in the Galactic halo without escaping from the gravitational potential of the Galaxy. The gas gradually started to accrete to the disk around five billion years ago, corresponding to the time of sun's birth, and replaced a low-metallicity halo gas that had been accreting over nearly ten billion years. The metal-rich infalling gas, whose elemental abundance reflects that of metal-rich bulge stars, mixed with the interstellar gas already present in the disk. Stars formed from the mixture compose the metal-rich stellar disk.

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 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 Interstellar Extinction and Elemental Abundances: Individual Sight Lines

2021 ◽  
Vol 257 (2) ◽  
pp. 63
Author(s):  
Wenbo Zuo ◽  
Aigen Li ◽  
Gang Zhao
Keyword(s):  
Gas Phase ◽  
Interstellar Extinction ◽  
Elemental Abundance ◽  
Extinction Curve ◽  
Galactic Chemical Evolution ◽  
Space Telescopes ◽  
Dust Extinction ◽  
Elemental Abundances ◽  
Hydrogen Column Density ◽  
The Relationship

Abstract While it is well recognized that both the Galactic interstellar extinction curves and the gas-phase abundances of dust-forming elements exhibit considerable variations from one sight line to another, as yet most of the dust extinction modeling efforts have been directed to the Galactic average extinction curve, which is obtained by averaging over many clouds of different gas and dust properties. Therefore, any details concerning the relationship between the dust properties and the interstellar environments are lost. Here we utilize the wealth of extinction and elemental abundance data obtained by space telescopes and explore the dust properties of a large number of individual sight lines. We model the observed extinction curve of each sight line and derive the abundances of the major dust-forming elements (i.e., C, O, Si, Mg, and Fe) required to be tied up in dust (i.e., dust depletion). We then confront the derived dust depletions with the observed gas-phase abundances of these elements and investigate the environmental effects on the dust properties and elemental depletions. It is found that for the majority of the sight lines the interstellar oxygen atoms are fully accommodated by gas and dust and therefore there does not appear to be a “missing oxygen” problem. For those sight lines with an extinction-to-hydrogen column density A V /N H ≳ 4.8 × 10−22 mag cm2 H−1 there are shortages of C, Si, Mg, and Fe elements for making dust to account for the observed extinction, even if the interstellar C/H, Si/H, Mg/H, and Fe/H abundances are assumed to be protosolar abundances augmented by Galactic chemical evolution.

scholarly journals Carbon Isotopic Chemistry

1992 ◽  
Vol 150 ◽  
pp. 193-197
Author(s):  
W. D. Langer
Keyword(s):  
Chemical Evolution ◽  
Galactic Chemical Evolution ◽  
Interstellar Clouds ◽  
Carbon Isotopic ◽  
The Galaxy ◽  
Molecular Abundances

Isotopic molecular abundances are used to interpret Galactic chemical evolution and the properties of interstellar clouds. The isotopic chemistry of carbon plays an important role in the interpretation of these measurements. This paper reviews the recent measurements of the carbon twelve to thirteen ratio across the Galaxy and the isotopic chemistry.

Developing an astrophysical line list for Keck/Nirspec observations of red giants in the Galactic centre

2017 ◽  
Vol 13 (S334) ◽  
pp. 372-373 ◽  
Author(s):  
B. Thorsbro ◽  
N. Ryde ◽  
R. M. Rich ◽  
M. Schultheis ◽  
T. K. Fritz ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Wavelength Region ◽  
Galactic Centre ◽  
Red Giants ◽  
The Sun ◽  
Galactic Chemical Evolution ◽  
Line List ◽  
Stellar Spectroscopy ◽  
Near Ir ◽  
The Galaxy

AbstractA major avenue in the study of the Galaxy is the investigation of stellar populations and Galactic chemical evolution by stellar spectroscopy. Due to the dust obscuration, stars in the centre of the Galaxy can only be observed in the near-IR wavelength region. However, existing line lists in this wavelength region are demonstratively not of good enough quality for use in stellar spectroscopy. In response to this, we have developed an empirical astrophysical line list in the K-band based on modelling against the Sun and testing against Arcturus. Of ca. 700 identified interesting lines about 570 lines have been assigned empirically determined values.

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 Nucleosynthesis yields of core-collapse supernovae and hypernovae, and galactic chemical evolution

2006 ◽  
Vol 777 ◽  
pp. 424-458 ◽  
Author(s):  
Ken'ichi Nomoto ◽  
Nozomu Tominaga ◽  
Hideyuki Umeda ◽  
Chiaki Kobayashi ◽  
Keiichi Maeda
Keyword(s):  
Chemical Evolution ◽  
Core Collapse ◽  
Galactic Chemical Evolution

scholarly journals The chemical evolution of iron-peak elements with hypernovae

2020 ◽  
Vol 496 (4) ◽  
pp. 4987-5001 ◽  
Author(s):  
J J Grimmett ◽  
Amanda I Karakas ◽  
Alexander Heger ◽  
Bernhard Müller ◽  
Christopher West
Keyword(s):  
Chemical Evolution ◽  
Significant Contribution ◽  
Extreme Values ◽  
Occurrence Rate ◽  
A Value ◽  
The Galaxy ◽  
Low Metallicity ◽  
Homogeneous Chemical ◽  
The Mean ◽  
Peak Abundance

ABSTRACT We calculate the mean evolution of the iron-peak abundance ratios [(Cr, Mn, Co, Zn)/Fe] in the Galaxy, using modern supernova and hypernova (HN) chemical yields and a Galactic Chemical Evolution code that assumes homogeneous chemical evolution. We investigate a range of HN occurrence rates and are able to produce a chemical composition that is a reasonable fit to the observed values in metal-poor stars. This requires an HN occurence rate that is large (50 per cent) in the early Universe, decreasing throughout evolution to a value that is within present-day observational constraints ($\lesssim 1{{\ \rm per\ cent}}$). A large HN occurrence rate is beneficial to matching the high [Zn/Fe] observed in the most metal-poor stars, although including HNe with progenitor mass $\ge 60\, \mathrm{M}_\odot$ is detrimental to matching the observed [(Mn, Co)/Fe] evolution at low [Fe/H]. A significant contribution from HNe seems to be critical for producing supersolar [(Co, Zn)/Fe] at low metallicity, though more work will need to be done in order to match the most extreme values. We also emphasize the need to update models for the enrichment sources at higher metallicity, as the satisfactory recovery of the solar values of [(Cr, Mn, Co, Zn)/Fe] still presents a challenge.

scholarly journals Non-LTE Abundances in OB stars: Preliminary Results for 5 Stars in the Outer Galactic Disk

2014 ◽  
Vol 9 (S307) ◽  
pp. 90-91
Author(s):  
G. A. Bragançca ◽  
T. Lanz ◽  
S. Daflon ◽  
K. Cunha ◽  
C. D. Garmany ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Galactic Disk ◽  
B Stars ◽  
Large Sample ◽  
Ob Stars ◽  
Preliminary Results ◽  
Elemental Abundances ◽  
The Galaxy ◽  
Ionization Equilibria ◽  
Chemical Distribution

AbstractThe aim of this study is to analyse and determine elemental abundances for a large sample of distant B stars in the outer Galactic disk in order to constrain the chemical distribution of the Galactic disk and models of chemical evolution of the Galaxy. Here, we present preliminary results on a few stars along with the adopted methodology based on securing simultaneous O and Si ionization equilibria with consistent NLTE model atmospheres.

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