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Browsing by Author "Kobayashi, Chiaki"
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Common Envelope Jet Supernova r -process Yields Can Reproduce [Eu/Fe] Abundance Evolution in the Galaxy
Grichener, Aldana; Kobayashi, Chiaki; Soker, Noam (2022-02-16)We use a numerical Galactic chemical evolution model and find that the common envelope jet supernova (CEJSN) r-process scenario can account for both the very early average ratio of europium to iron and its evolution at ... -
Common envelope jets supernova r-process yields can reproduce $\rm [Eu/Fe]$ abundance evolution in the Galaxy
Grichener, Aldana; Kobayashi, Chiaki; Soker, Noam (2022-02-16)We use a numerical Galactic chemical evolution model and find that the common envelope jets supernova (CEJSN) r-process scenario can account for both the very early average ratio of europium to iron and its evolution at ... -
Constraining cosmic scatter in the Galactic halo through a differential analysis of metal-poor stars
Reggiani, Henrique; Meléndez, Jorge; Kobayashi, Chiaki; Karakas, Amanda; Placco, Vinicius (2017-12)Context. The chemical abundances of metal-poor halo stars are important to understanding key aspects of Galactic formation and evolution. Aims. We aim to constrain Galactic chemical evolution with precise chemical abundances ... -
Constraining cosmic scatter in the Galactic halo through a differential analysis of metal-poor stars
Reggiani, Henrique; Meléndez, Jorge; Kobayashi, Chiaki; Karakas, Amanda; Placco, Vinicius (2017-12)Context. The chemical abundances of metal-poor halo stars are important to understanding key aspects of Galactic formation and evolution. Aims. We aim to constrain Galactic chemical evolution with precise chemical abundances ... -
Constraints on the formation of the galactic bulge from Na, Al, and heavy-element abundances in Plaut's field.
Johnson, Christian I.; Rich, R. Michael; Kobayashi, Chiaki; Fulbright, Jon P. (2012-04-05)We report chemical abundances of Na, Al, Zr, La, Nd, and Eu for 39 red giant branch (RGB) stars and 23 potential inner disk red clump stars located in Plaut's low-extinction window. We also measure lithium for a super ... -
Cosmic Rates of Black Hole Mergers and Pair-Instability Supernovae from Chemically Homogeneous Binary Evolution
Buisson, Lise du; Marchant, Pablo; Podsiadlowski, Philipp; Kobayashi, Chiaki; Abdalla, Filipe B.; Taylor, Philip; Mandel, Ilya; Mink, Selma E. de; Moriya, Takashi J.; Langer, Norbert (2020-10-16)During the first three observing runs of the Advanced gravitational-wave detector network, the LIGO/Virgo collaboration detected several black hole binary (BHBH) mergers. As the population of detected BHBH mergers grows, ... -
Cosmic supernova rate history and Type Ia supernova progenitors
Nomoto, K; Tsujimoto, T; Kobayashi, Chiaki (World Scientific Publishing, 2001)Adopting a single degenerate scenario for Type Ia supernova progenitors with the metallicity effect, we make a prediction of the cosmic supernova rate history as a composite of the supernova rates in spiral and elliptical ... -
Cosmic supernova rates in cluster vs. field galaxies
Kobayashi, Chiaki; Tsujimoto, T; Nomoto, K (1999) -
Early-type galaxies at large galactocentric radii - II. Metallicity gradients and the [Z/H]-mass, [alpha/Fe]-mass relations
Spolaor, Max; Kobayashi, Chiaki; Forbes, Duncan A.; Couch, Warrick J.; Hau, George K. T. (2010-10-11)We present the results of a study of stellar population properties at large galactocentric radii of 14 low-mass early-type galaxies in the Fornax and Virgo clusters. We derive radial profiles of age, total metallicity [Z/H] ... -
The effects of AGN feedback on present-day galaxy properties in cosmological simulations
Taylor, Philip; Kobayashi, Chiaki (2015-04-01)We show that feedback from active galactic nuclei (AGN) plays an essential role in reproducing the down-sizing phenomena, namely: the colour–magnitude relation; specific star formation rates; and the α enhancement of ... -
Elemental and isotopic abundances and chemical evolution of galaxies
Kobayashi, Chiaki (Astronomical Society of the Pacific, 2012-02-15)Elemental and isotopic abundances are the fossils of galactic archaeology. The observed [X/Fe]-[Fe/H] relations in the Galactic bulge and disk and the mass-metallicity relation of galaxies are roughly reproduced with ... -
Elevated r-process enrichment in Gaia Sausage and Sequoia
Aguado, David S.; Belokurov, Vasily; Myeong, G. C.; Evans, N. Wyn; Kobayashi, Chiaki; Sbordone, Luca; Chanamé, Julio; Navarrete, Camila; Koposov, Sergey E. (2021-02-10)The Gaia Sausage and the Sequoia represent the major accretion events that formed the stellar halo of the Milky Way. A detailed chemical study of these main building blocks provides a pristine view of the early steps of ... -
Evolution of dust extinction and supernova cosmology
Totani, T; Kobayashi, Chiaki (1999-12-01)We have made a quantitative calculation for the systematic evolution of the average extinction by interstellar dust in host galaxies of high-redshift Type Ia supernovae by using a realistic model of photometric and chemical ... -
Evolution of fluorine in the galaxy with the v-process
Kobayashi, Chiaki; Izutani, Natsuko; Karakas, Amanda I.; Yoshida, Takashi; Yong, David; Umeda, Hideyuki (2011-10-01)We calculate the evolution of fluorine in the solar neighborhood with the v-process of core-collapse supernovae, the results of which are in good agreement with the observations of field stars. The v-process operating in ... -
The evolution of isotope ratios in the Milky Way Galaxy
Kobayashi, Chiaki; Karakas, Amanda I.; Umeda, Hideyuki (2011-07)Isotope ratios have opened a new window into the study of the details of stellar evolution, supernovae and galactic chemical evolution. We present the evolution of the isotope ratios of elemental abundances (from C to Zn) ... -
Evolution of N/O ratios in galaxies from cosmological hydrodynamical simulations
Vincenzo, Fiorenzo; Kobayashi, Chiaki (2018-07-21)We study the redshift evolution of the gas-phase O/H and N/O abundances, both (i) for individual interstellar medium (ISM) regions within single spatially resolved galaxies and (ii) when dealing with average abundances in ... -
Explosive nucleosynthesis in massive Pop III stars and abundances in metal-poor stars and M87
Shirouzu, M; Kobayashi, Chiaki; Umeda, H; Nomoto, K (Astronomical Society of the Pacific, 2001)In order to understand the elemental abundance pattern observed in galaxies and clusters of galaxies of various metallicity, we investigate stability, evolution and explosion of massive population III stars. We find the ... -
Extragalactic archaeology with the C, N, and O chemical abundances
Vincenzo, Fiorenzo; Kobayashi, Chiaki (2018-02-09)We predict how the C, N, and O abundances within the interstellar medium of galaxies evolve as functions of the galaxy star formation history (SFH). We adopt a hydrodynamical cosmological simulation, focusing on three ... -
Faint Population III supernovae as the origin of the most iron-poor stars
Ishigaki, Miho N.; Tominaga, Nozomu; Kobayashi, Chiaki; Nomoto, Ken'ichi (2014-08-26)The most iron-deficient stars in the Milky Way provide important observational constraints on the nature of astrophysical objects that have enriched the primordial gas with heavy elements from which these stars were formed. ... -
A formation timescale of the Galactic halo from Mg isotopes in dwarf stars
Carlos, Marilia; Karakas, Amanda I.; Cohen, Judith G.; Kobayashi, Chiaki; Melendez, Jorge (2018-04-04)We determine magnesium isotopic abundances of metal-poor dwarf stars from the galactic halo, to shed light on the onset of asymptotic giant branch (AGB) star nucleosynthesis in the galactic halo and constrain the timescale ...