2 research outputs found
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 1--2 solar. The /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