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Post Info TOPIC: Sagittarius A East


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RE: Sagittarius A East

NASA's SOFIA Finds Missing Link Between Supernovae and Planet Formation

Using NASA's Stratospheric Observatory for Infrared Astronomy (SOFIA), an international scientific team discovered that supernovae are capable of producing a substantial amount of the material from which planets like Earth can form.
The research team, headed by Lau, used SOFIA's airborne telescope and the Faint Object InfraRed Camera for the SOFIA Telescope, FORCAST, to take detailed infrared images of an interstellar dust cloud known as Supernova Remnant Sagittarius A East, or SNR Sgr A East.

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Title: Three-Dimensional Observations of H_2 Emission around Sgr A East - I. Structure in the Central 10 Parsecs of Our Galaxy
Authors: Sungho Lee, Soojong Pak, Minho Choi, Christopher J. Davis, T. R. Geballe, Robeson M. Herrnstein, Paul T. P. Ho, Y. C. Minh, Sang-Gak Lee

We have obtained velocity-resolved spectra of the H_2 v=1-0 S(1) (lambda = 2.1218 micron) emission line at 2 arcsec angular resolution (or 0.08 pc spatial resolution) in four regions within the central 10 pc of the Galaxy where the supernova-like remnant Sgr A East is colliding with molecular clouds. To investigate the kinematic, physical, and positional relationships between the important gaseous components in the centre, we compared the H_2 data cube with previously published NH_3 data. The projected interaction-boundary of Sgr A East is determined to be an ellipse with its centre offset 1.5 pc from Sgr A* and dimensions of 10.8 pc X 7.6 pc. This H_2 boundary is larger than the synchrotron emission shell but consistent with the dust ring which is believed to trace the shock front of Sgr A East. Since Sgr A East is driving shocks into its nearby molecular clouds, we can determine their positional relationships using the shock directions as indicators. As a result, we suggest a revised model for the three-dimensional structure of the central 10 pc. The actual contact between Sgr A East and all of the surrounding molecular material, including the circum-nuclear disk and the southern streamer, makes the hypothesis of infall into the nucleus and feeding of Sgr A* very likely.

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Title: A Candidate Neutron Star Associated with Galactic Center Supernova
Remnant Sagittarius A East

Authors: Sangwook Park (Penn State), Michael P. Muno (UCLA), Frederick K.
Baganoff (MIT), Yo****omo Maeda (ISAS), Mark Morris (UCLA), George Chartas
(Penn State), Divas Sanwal (Penn State), David N. Burrows (Penn State), and
Gordon P. Garmire (Penn State)
Comments: ApJ preprint style 28 pages, 1 color fig (fig1), Accepted by ApJ
We present imaging and spectral studies of the supernova remnant (SNR)
Sagittarius (Sgr) A East from deep observations with the Chandra X-Ray Observatory. The spatially-resolved spectral analysis of Sgr A East reveals the presence of a two-temperature thermal plasma (kT _ 1 keV and 5 keV) near the center
of the SNR. The central region is dominated by emission from highly-ionized iron rich ejecta.
We estimate a conservative upper limit on the total Fe ejecta mass
of the SNR, MFe less than 0.27 M⊙. Comparisons with standard SN nucleosynthesis models suggest that this Fe mass limit is consistent with a Type II Supernova explosion for the origin of Sagittarius A East.
On the other hand, the soft X-ray emission extending toward the north of the SNR can be described by a single-temperature (kT_ 1.3 keV) thermal plasma with normal chemical composition. This portion of the supernova remnant is thus X-ray emission from the heated interstellar medium rather than the metal-rich stellar ejecta.
We point out that a hard pointlike source CXOGC J174545.5-285829 (the so-called “cannonball”) at the northern edge of the supernova remnant shows unusual X-ray characteristics among other Galactic centre sources. The
morphological, spectral, and temporal characteristics of this source suggest an identification as a high-velocity neutron star.
Based on the suggested Type II origin for the SNR Sgr A East and the proximity between the two, we propose that CXOGC J174545.5-285829 is a high-velocity neutron star candidate, born from the core-collapse supernova which also created the supernova remnant Sgr A East.


(Fixed this link - Ed)

-- Edited by Blobrana at 22:18, 2005-06-10

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