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RESEARCH PRODUCT

Simulations with Smoothed Particles Confirm Stationary Shocks in Accretion Flows onto Black Holes

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We present the results of time dependent numerical simulations of the accretion of gas onto Schartzschild black holes. We find that stable shocks are a common feature for flows of inviscid gas accreting with small angular momentum per unit mass. We used the Smoothed Particles Hydrodynamics tecnique, expressed into cylindrical coordinates to exploit the axial symmetry of the problem. For the case of 1-Dimensional axis-symmetric simulations we find that the shock location is exactly at the position predicted by the stationary analysis developed by Chakrabarti. We solve also the ambiguity related to the two possible shock positions: only the outer shock is stable. The case of 2-Dimensional axis-symmetric simulations exhibits a great variety of results: in general we can say that shocks are quite commonly formed, even more easily than for the 1-D case; it is also found that an important role is played by the vertical speed of the gas that produces an extra compression helping shock formation; the production of strong outflowing wind is also a common feature whenever a shock is formed