Numerical results

Now we have verified that the basic properties of Sgr A^* can be explained with a synchrotron +SSC jet model, we can consider a more sophisticated numerical approach. This has been outlined in Falcke and Markoff (2000), Markoff et al (2001), and Yuan et al (2002).

We start with the basic jet emission model (Falcke and Biermann 1999, Falcke and Markoff 2000), consisting of a conical jet with pressure gradient, nozzle and relativistic effects. The parameters in the nozzle for the quiescent state are determined from the underlying accretion disk, assumed to be an ADAF, as described in Yuan et al (2002). All quantities further out in the jet are solved by using conservation of mass and energy, and the Euler equation for the accelerating velocity field. The results are shown in figures 1.1 and show that the model is able to reproduce the observed spectrum and size in detail.

Figure 1.1. The jet-disk spectral model for Sgr A^*. The dotted line is for the ADAF (optically thin, advection dominated accretion flow) contribution, the dashed line is for the jet emission, and the full line shows their sum. For the most part, the emission is dominated by the jet spectrum. The sub-mm bump is produced by the jet nozzle with a possible contribution from the accretion flow. The X-ray emission is largely SSC emission from the nozzle with a slight contribution from the more extended thermal X-ray emission from the accretion flow. We have here assumed an accretion rate of 10⁻⁶ M_ּ yr⁻¹, where only 0.1% of the power goes into the jet. For a 10% efficiency the required accretion rate is about 10⁻⁸ M_ּ yr⁻¹ and the disk contribution would be negligible. The model is discussed in more detail in Yuan et al (2002).