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Galactic Center Research


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The image summarizes the central parsec (23") of our Galaxy in the near infrared and the kind of data that are available:

  • Center: 0.15" K-Band image taken with the SHARP camera on the ESO-NTT.

  • Right, top and bottom left insets: K-band spectra of several of the stars (blue supergiants, red supergiants/AGB stars) and of the SgrA* region (circled), taken with the MPE 3D spectrometer and with ISAAC.

  • Bottom left: The embedded, presumably very young star IRS 1 has a reddened, featureless spectrum (the Br gamma emission line is due to the ionized gas of the so-called "mini-spiral" in the central parsec).

  • Top: Spectrum of the HeI emitting star IRS 16C, that forms part of the IRS 16 complex of bright, young HeI emitting stars close to SgrA*.

  • Top and bottom right: CO absorption features in the spectra of IRS 7 and IRS 14N.

  • Middle right insets: Spectra of the Wolf-Rayet star, IRS 13E, and of the SgrA* cluster. The spectrum of the northern part of the SgrA* cluster suggests that its brighter members are main sequence OB V type stars.

  • Left and top left insets. Proper motions in the center of the Galaxy, obtained with the MPE SHARP camera on the ESO NTT. Shown are the proper motion vectors superposed on a 0.15" SHARP/NTT 2µm image of the central ~10" (top, cross is SgrA*) and on a 0.05" Keck image of the central 1" region around SgrA* (bottom, asterisk denotes position of SgrA*).

Overview of the central parsec

The combination of observations of Sgr A* in different wavelength regimes (from X-ray to radio) allows a description of the spectral energy distribution of the emitted radiation and the construction of emission models.

Spectral Energy Distribution of Sgr A*

Spectral energy distribution of the emission from Sgr A*. This plot shows the extinction and absorption corrected luminosities. All error bars are ±1 sigma and include statistical and systematic errors. Black triangles denote the radio spectrum of Sgr A*. Open grey circles mark various infrared upper limits from the literature. The three X-ray data ranges are (from bottom to top) the quiescent state as determined with Chandra (black; Baganoff et al., 2003), the autumn 2000 Chandra flare (red; Baganoff et al., 2000), and the autumn 2002 flare observed by XMM (light blue; Porquet et al., 2003). Open red squares with crosses mark the de-reddened peak emission (minus quiescent emission) of the four NIR flares. Open blue circles mark the de-reddened H, KS, and L' luminosities of the quiescent state, derived from the local background subtracted flux density of the point source at the position at Sgr A*, thus eliminating the contribution from extended, diffuse light due to the stellar cusp around Sgr A*.


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