Workshop: Gas Dynamics and Star Formation in the Extreme Environment of Galactic Nuclei, Ringberg

Simulating SMBH accretion: spherical flow to cold clumps and hot bubbles

21 Mar 2013, 17:05

25m

Ringberg

Talk Accretion physics (radiatively efficient and inefficient)

Speaker

Paramita Barai (INAF - Osservatorio Astronomico di Trieste)

Description

I will report our investigation of gas accretion and radiative feedback in the SMBH of active galaxies (Barai, Proga & Nagamine 2011, 2012). We perform simulations using the 3D SPH code Gadget-3, without and with radiative heating by the central X-ray source and cooling. We find that the accretion mode depends on the X-ray luminosity (L_X). At low-L_X, gas accretes in a stable, spherically-symmetric fashion. At high-L_X, the inner gas is heated up and expands, turning into a strong outflow. For some intermediate-L_X, the flow becomes unstable developing prominent non-spherical features, the key reason for which is found to be thermal instability (TI). The gas fragments to form cold and dense clumps infalling as filamentary structures, surrounded by hot, low-density bubbles of outflowing gas. Such TI-driven gas fragmentation can contribute to the formation of clouds and stars in narrow and broad line regions of AGN, and the observed variability of the AGN luminosity.

Presentation materials

Slides

Barai.pdf