Ray Imaging and Spectroscopy of Sgr A East

Most of the emission within the central few arcminutes comes from a region within the radio shell of Sgr A East. The brightest spot corresponds to the location of Sgr A*. The X-ray region around Sgr A* is found to be extended given the angular resolution of XMM-Newton, whereas the Chandra Observatory with its 0.5" resolution could resolve a few more sources within the innermost 10". With the CCD detectors onboard of XMM-Newton and Chandra Observatory, it became possible for the first time to combine high resolution imaging with good spectroscopic performance. Since the Galactic Center region is known to be full of molecular clouds producing different amounts of absorption, a spectral analysis of an extended region requires a model of patchy absorption. The average fitted temperature of Sgr A East is about 2-4 keV. The various element abundance across the SNR is remarkable: it seems that iron is overabundant (Z « 3.5) at the center of the SNR and less abundant in the outer regions (Z « 0.5), whereas the other metals do not significantly vary within Sgr A East from solar abundances [22]. At the rim of the remnant, a 6.4 keV iron fluorescent line is detected. This outer region is nearly coincident with the observed dust ring [12]. Hence, the detection of the neutral iron line supports the idea that Sgr A East is surrounded by the dust shell, or Sgr A East is interacting with the molecular ridge.

19.2.3 Bipolar Lobes

There is further X-ray emission to the north-east along the Galactic plane, emission that was also seen before by the Einstein Observatory, ROSAT, and ASCA (Fig. 19.5).

A number of diffuse, extended structures are present in the image, but the most prominent of them are aligned along a line passing through the center of Sgr A East (or better: Sgr A*) and oriented perpendicular to the Galactic plane. These "bipolar lobes" [13] apparently are filled structures with discernible sharp edges. Thermal fits to the blobs (i.e., the brightest regions within the lobes) give temperatures around 2 keV on average. A compelling interpretation for the bipolar lobes straddling Sgr A* is that they result from energetic mass ejections or explosions from the immediate environment of Sgr A*, presumably from an accretion disk.

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