43 research outputs found
Evolution of newly formed dust in Population III supernova remnants and its impact on the elemental composition of Population II.5 stars
We investigate the evolution of dust formed in Population III supernovae
(SNe) by considering its transport and processing by sputtering within the SN
remnants (SNRs). We find that the fates of dust grains within SNRs heavily
depend on their initial radii . For Type II SNRs expanding into
the ambient medium with density of cm, grains of
m are detained in the shocked hot gas and are
completely destroyed, while grains of m are injected
into the surrounding medium without being destroyed significantly. Grains with
= 0.05-0.2 m are finally trapped in the dense shell behind
the forward shock. We show that the grains piled up in the dense shell enrich
the gas up to 10 , high enough to form low-mass stars
with 0.1-1 . In addition, [Fe/H] in the dense shell ranges from -6 to
-4.5, which is in good agreement with the ultra-metal-poor stars with [Fe/H] <
-4. We suggest that newly formed dust in a Population III SN can have great
impacts on the stellar mass and elemental composition of Population II.5 stars
formed in the shell of the SNR.Comment: 5 pages, 3 figures and 1 table. To appear in the proceedings of IAU
Symposium 255 "Low-Metallicity Star Formation: From the First Stars to Dwarf
Galaxies", Rapallo, June 2008, eds. L.K. Hunt, S. Madden, & R. Schneider
(Cambridge Univ. Press
Dust in Supernovae; Formation and Evolution
Core--collapsed supernovae (CCSNe) have been considered to be one of sources
of dust in the universe. What kind and how much mass of dust are formed in the
ejecta and are injected into the interstellar medium (ISM) depend on the type
of CCSNe, through the difference in the thickness (mass) of outer envelope. In
this review, after summarizing the existing results of observations on dust
formation in CCSNe, we investigate formation of dust in the ejecta and its
evolution in the supernova remnants (SNRs) of Type II--P and Type IIb SNe.
Then, the time evolution of thermal emission from dust in the SNR of Type IIb
SN is demonstrated and compared with the observation of Cas A. We find that the
total dust mass formed in the ejecta does not so much depend on the type; in Type II--P SNe and in Type IIb SN.
However the size of dust sensitively depends on the type, being affected by the
difference in the gas density in the ejecta: the dust mass is dominated by
grains with radii larger than 0.03 m in Type II-P, and less than 0.006
m in Type IIb, which decides the fate of dust in the SNR. The surviving
dust mass is in the SNRs of Type II--P SNe for the
ambient hydrogen density of cm, while almost all
dust grains are destroyed in the SNR of Type IIb. The spectral energy
distribution (SED) of thermal emission from dust in SNR well reflects the
evolution of dust grains in SNR through erosion by sputtering and stochastic
heating. The observed SED of Cas A SNR is reasonably reproduced by the model of
dust formation and evolution for Type IIb SN.Comment: correction of the typos in Table 3 and in the tex
Supernova Nucleosynthesis and Extremely Metal-Poor Stars
We investigate hydrodynamical and nucleosynthetic properties of the
jet-induced explosion of a population III star and compare the
abundance patterns of the yields with those of the metal-poor stars. We
conclude that (1) the ejection of Fe-peak products and the fallback of
unprocessed materials can account for the abundance patterns of the extremely
metal-poor (EMP) stars and that (2) the jet-induced explosion with different
energy deposition rates can explain the diversity of the abundance patterns of
the metal-poor stars. Furthermore, the abundance distribution after the
explosion and the angular dependence of the yield are shown for the models with
high and low energy deposition rates and . We also find that the
peculiar abundance pattern of a Si-deficient metal-poor star HE 1424--0241 can
be reproduced by the angle-delimited yield for of
the model with .Comment: 6 pages, 3 figures. To appear in "ORIGIN OF MATTER AND EVOLUTION OF
GALAXIES: From the Dawn of Universe to the Formation of Solar System", AIP
Conf. Proc. 1016 (December 2007, Sapporo), eds. T. Suda, T. Nozawa, et al.
(Melville: AIP
Formation and Evolution of Dust in Type IIb Supernova with Application to the Cassiopeia A Supernova Remnant
We investigate the formation of dust grains in the ejecta of a SN IIb and
their evolution in the shocked gas in the SNR by considering the uniform and
power-law density structures for the CSM. Based on these calculations, we also
simulate the time evolution of thermal emission from the shock-heated dust in
the SNR and compare the results with the observations of Cas A SNR. We find
that the total mass of dust formed in the SN IIb is as large as 0.167 M_sun but
the average radius of dust is smaller than 0.01 mum and is significantly
different from those in SNe II-P with the massive H-envelope. In the explosion
with the small-mass H-envelope, the expanding He core undergoes little
deceleration, so that the gas density in the He core is too low for large-sized
grains to form. In addition, the low-mass H-envelope of the SN IIb leads to the
early arrival of the reverse shock at the dust-forming region. If the CSM is
more or less spherical, therefore, the newly formed grains would be completely
destroyed in the relatively dense shocked gas for the CSM density of n_H > 0.1
cm^{-3}. However, the actual CSM is likely to be non-spherical, so that a part
of grains could be ejected into the ISM without being shocked. We demonstrate
that the time evolution of the SED by thermal dust emission is sensitive to the
ambient gas density and structure that affects the passage of the reverse shock
into the ejecta. Thus, the SED evolution well reflects the evolution of dust
through erosion by sputtering and stochastic heating. For Cas A, we consider
the CSM produced by the steady mass loss of ~8x10^{-5} M_sun/yr during the
supergiant phase. Then we find the infrared SED of Cas A is reasonably
reproduced by thermal emission from the newly formed dust of 0.08 M_sun, which
consists of 0.008 M_sun shocked warm dust and 0.072 M_sun unshocked cold dust.Comment: 50 pages, 17 figures, 3 tables. Accepted for publication in Ap
Biological and Pathological Studies of Rosmarinic Acid as an Inhibitor of Hemorrhagic Trimeresurus flavoviridis (habu) Venom
In our previous report, rosmarinic acid (RA) was revealed to be an antidote active compound in Argusia argentea (family: Boraginaceae). The plant is locally used in Okinawa in Japan as an antidote for poisoning from snake venom, Trimeresurus flavoviridis (habu). This article presents mechanistic evidence of RA’s neutralization of the hemorrhagic effects of snake venom. Anti-hemorrhagic activity was assayed by using several kinds of snake venom. Inhibition against fibrinogen hydrolytic and collagen hydrolytic activities of T. flavoviridis venom were examined by SDS-PAGE. A histopathological study was done by microscopy after administration of venom in the presence or absence of RA. RA was found to markedly neutralize venom-induced hemorrhage, fibrinogenolysis, cytotoxicity and digestion of type IV collagen activity. Moreover, RA inhibited both hemorrhage and neutrophil infiltrations caused by T. flavoviridis venom in pathology sections. These results demonstrate that RA inhibited most of the hemorrhage effects of venom. These findings indicate that rosmarinic acid can be expected to provide therapeutic benefits in neutralization of snake venom accompanied by heat stability
Conserved and Diverse Transcriptional Reprogramming Triggered by the Establishment of Symbioses in Tomato Roots Forming <i>Arum</i>-Type and <i>Paris</i>-Type Arbuscular Mycorrhizae
Arbuscular mycorrhizal (AM) fungi allocate mineral nutrients to their host plants, and the hosts supply carbohydrates and lipids to the fungal symbionts in return. The morphotypes of intraradical hyphae are primarily determined on the plant side into Arum- and Paris-type AMs. As an exception, Solanum lycopersicum (tomato) forms both types of AMs depending on the fungal species. Previously, we have shown the existence of diverse regulatory mechanisms in Arum- and Paris-type AM symbioses in response to gibberellin (GA) among different host species. However, due to the design of the study, it remained possible that the use of different plant species influenced the results. Here, we used tomato plants to compare the transcriptional responses during Arum- and Paris-type AM symbioses in a single plant species. The tomato plants inoculated with Rhizophagus irregularis or Gigaspora margarita exhibited Arum- and Paris-type AMs, respectively, and demonstrated similar colonization rates and shoot biomass. Comparative transcriptomics showed shared expression patterns of AM-related genes in tomato roots upon each fungal infection. On the contrary, the defense response and GA biosynthetic process was transcriptionally upregulated during Paris-type AM symbiosis. Thus, both shared and different transcriptional reprogramming function in establishing Arum- and Paris-type AM symbioses in tomato plants
Dust Evolution in Population III Supernova Remnants
We present the results of calculations for the evolution of dust within Population III supernova remnants (SNRs), focusing on the dust formed in the unmixed ejecta of Type II SNe. We show that once dust grains inside the He core encounter the reverse shock, they are subject to different fates depending on their initial sizes a_ini. For SNRs expanding into the interstellar medium (ISM) with n_[H,0] = 1 cm^[-3], grains of a_ini 0.2μm are injected into the ISM without significant destruction. The total mass of surviving dust is 0.01 to 0.8 M☉ and is higher for the lower ISM gas density. We also investigate the elemental abundances of the second-generation stars that form in the dense shell of Population III SNRs, based on the elemental composition of dust piled up in the shell. The comparison of those results with the observations of hyper-metal poor (HMP) stars indicates that the transport of dust segregated from metal-rich gas within a SNR can be responsible for the abundance patterns of Mg and Si in HMP stars.First Stars III: First Stars II Conference. Santa Fe, New Mexico, U.S.A. 15–20 July 2007
Evolution of Dust in Primordial Supernova Remnants and Its Influence on the Elemental Composition of Hyper-Metal-Poor Stars
The calculations for the evolution of dust within Population III supernova remnants (SNRs) are presented, based on the models of dust formed in the unmixed ejecta of Type II SNe. We show that once dust grains collide with the reverse shock penetrating into the ejecta, their fates strongly depend on the initial radius a_ini. For SNRs expanding into the interstellar medium (ISM) with n_[H,0] = 1 cm^[−3], grains of a_ini0.2 µm are injected into the ISM without being eroded significantly. The total mass of surviving dust is 0.01 to 0.8 M☉ for n_[H,0] = 10 to 0.1 cm^[−3]. We also investigate the influence of the piled-up dust on the elemental abundances of the second-generation stars formed in the dense shell of Population III SNRs. The comparison of the calculated elemental abundances with those observed in hyper-metal-poor (HMP) and ultra-metal-poor (UMP) stars indicates that the transport of dust separated from metal-rich gas can be an important process in determining the abundance patterns of Mg and Si in HMP and UMP stars.Origin of Matter and Evolution of Galaxies: The 10th International Symposium on Origin of Matter and Evolution of Galaxies: From the Dawn of Universe to the Formation of Solar System. 4–7 December 2007. Sapporo, Japan