Outflow from unmagnetized shocked radiative transonic accretion disk around a black hole

Abstract

We study outflow from an unmagnetized, shocked accretion disk around a non-rotating super-massive black hole using multidimensional hydrodynamics simulation with radiative cooling. We aim to investigate whether such shocked accretion flow can launch sustained collimated bipolar outflow reaching out to thousands of gravitational radii even in the absence of magnetic field and if yes, what terminal velocity can they achieve. We present the results of a few simulations of geometrically thick accretion flow with increasing specific angular momentum on a vertically elongated cylindrical domain. We show that bipolar outflow from a region very close to the black hole is originating and propagating vertically out to our simulation domain boundary at around 2651 Schwarzschild radius. The outflow attains a terminal velocity with a maximum value found to be 0.14c and the outflow rate depends on the angular momentum value of the accreting material. We also compute the self-Comptonized bremsstrahlung spectra for all the disk-jet runs.

Figures (9)

• Figure 1: shows the mass density distribution (in color) on log scale overlaid with velocity arrows at the final time for all cases A1-A5 (a:A1, b:A2, c:A3, d:A4, e:A5). Black color shows lower densities, and red color shows higher densities. Length of a velocity arrow is proportional to the magnitude $\sqrt{v_R^2+v_Z^2}$. Colors of arrows represent their magnitudes as shown in the legend for velocity vector. The maximum velocity is found extremely close to the black hole on the equatorial plane
• Figure 2: (a) shows a zoomed-in view of case A5 in the $R-Z$ domain $[0:150]\times[-160:160]$. We plot the number density (measured in number/cc) colormap overlaid with velocity arrows. The iso-density contour (green line) corresponding to the value $8.85\times10^6$, allows to identify the shock surface at $R\sim 100$. The region inside this contour is the high-density post-shock region, and the outer low-density region is the pre-shock region, marked accordingly. The post-shock region shows presence of turbulent vortices. We also mark the jet launching region close to the black hole. (b) This figure shows the temperature (in Kelvin) distribution in the same domain clearly separating the high-temperature post-shock region from the low-temperature pre-shock region for case A5.
• Figure 3: represents the radial variations (along the equator) of logarithm of temperature($T$), number density ($n$), and velocity ($v_R$) at the final time. Different quantities are translated by a scalar along vertical axis to bring on same scale. We show temperature in Kelvin, number density in number/cc and velocity in cm/s units.
• Figure 4: shows temporal variation of the CENBOL boundary at the equator for all cases. Cases A1 and A2 do not show shock formation, though a discontinuity due to centrifugal barrier is found. Cases A3, A4, and A5 show shock formation and oscillations of the CENBOL boundary over time.
• Figure 5: (a) shows a colormap of specific energy distribution for all cases A1-A5 at the final time. The high-energy matter is shown by red color, which forms the outflow. (b) shows the force vectors overlaid on the density colormap for case A3, clearly showing unidirectional force vectors beyond $-200$ and $200$ in the Z-direction. Force is calculated in units of $\frac{c^2}{r_g}.$