Hydrodynamic Evolution of Sgr A East: The Imprint of A Supernova Remnant in the Galactic Center

We perform three-dimensional numerical simulations to study the hydrodynamic evolution of Sgr A East, the only known supernova remnant (SNR) in the center of our Galaxy, to infer its debated progenitor SN type and its potential impact on the Galactic center environment. Three sets of simulations are performed, each of which represents a represent a certain type of SN explosion (SN Iax, SN Ia or core-collapse SN) expanding against a nuclear outflow of hot gas driven by massive stars, whose thermodynamical properties have been well established by previous work and fixed in the simulations. All three simulations can simultaneously roughly reproduce the extent of Sgr A East and the position and morphology of an arc-shaped thermal X-ray feature, known as the "ridge". Confirming previous work, our simulations show that the ridge is the manifestation of a strong collision between the expanding SN ejecta and the nuclear outflow. The simulation of the core-collapse SN, with an assumed explosion energy of 5x10^50 erg and an ejecta mass of 10 M_sun, can well match the X-ray flux of the ridge, whereas the simulations of the SN Iax and SN Ia explosions underpredict its X-ray emission, due to a smaller ejecta mass. All three simulations constrain the age of Sgr A East to be <1500 yr and predict that the ridge should fade out over the next few hundred years. We address the implications of these results for our understanding of the Galactic center environment.Comment: 21 pages, 18 figures. Accepted for publication on MNRA

Chandra X-ray Measurement of Gas-phase Heavy Element Abundances in the Central Parsec of the Galaxy

Elemental abundances are key to our understanding of star formation and evolution in the Galactic center. Previous work on this topic has been based on infrared (IR) observations, but X-ray observations have the potential of constraining the abundance of heavy elements, mainly through their K-shell emission lines. Using 5.7 Ms Chandra observations, we provide the first abundance measurement of Si, S, Ar, Ca and Fe, in four prominent diffuse X-ray features located in the central parsec of the Galaxy, which are the manifestation of shock-heated hot gas. A two-temperature, non-equilibrium ionization spectral model is employed to derive the abundances of these five elements. In this procedure, a degeneracy is introduced due to uncertainties in the composition of light elements, in particular, H, C and N. Assuming that the hot gas is H-depleted but C- and N-enriched, as would be expected for a standard scenario in which the hot gas is dominated by Wolf-Rayet star winds, the spectral fit finds a generally subsolar abundance for the heavy elements. If, instead, the light elements had a solar-like abundance, the heavy elements have a fitted abundance of $\sim$1--2 solar. The $\alpha$/Fe abundance ratio, on the other hand, is mostly supersolar and insensitive to the exact composition of the light elements. These results are robust against potential biases due to either a moderate spectral S/N or the presence of non-thermal components. Implications of the measured abundances for the Galactic center environment are addressed.Comment: 13 pages, 6 figures, Accepted for publication in MNRA

Effect of Yushen zhuyun decoction on rats with diminished ovarian reserve induced by tripterygium glycosides

Purpose: To investigate the effect of Yushen zhuyun decoction (YSZYF) on rats with diminished ovarian reserve (DOR).Methods: High-performance liquid chromatography (HPLC) was used to determine the major phytochemical constituents of YSZYF. Rats with DOR (DOR rats) were prepared by administration of tripterygium glycosides (TWP) orally (50 mg/kg) for 15 days. Thereafter, DOR rats were treated orally with YSZYF (300, 600 and 900 mg/kg). After 15 days’ treatment, ovary index was calculated and blood was obtained to determine serum levels of follicle-stimulating hormone (FSH), estradiol (E2), progesterone (P), testosterone (T), inhibin (INH) and anti-mullerian hormone (AMH) by radioimmunoassay and enzyme-linked immunosorbent assay (ELISA). In addition, the ovary was subjected to histopathological examinations.Results: Phytochemical investigation indicated that the major constituents of YSZYF are acteoside, loganin, lcariin and echinacoside. Compared to the control rats, YSZYF treatment enhanced the ovary index of DOR rat (p &lt; 0.05); furthermore, YSZYF treatment also enhanced the number of follicles and corpus luteum, as well as alleviated inflammatory reaction in ovary tissues. Additionally, the serum levels of FSH and T were elevated by treatment of YSZYF (p &lt; 0.01), whereas E2, INHB and AMH concentrations decreased (p &lt; 0.01), compared to control rats.Conclusion: The findings indicate that YSZYF improves ovarian reserve of DOR rats, and thus has a potential for treating infertility.Keywords: Yushen zhuyun decoction, Diminished ovarian reserve, Infertility, Acteoside, Loganin, Lcariin, Echinacosid