Abstract Details

Name: Nagendra Kumar
Affiliation: Indian Institute of Science, Bangalore-560012
Conference ID: ASI2021_201
Title : Wind outflow region in thin accretion disk in LLAGNs, as a favourable site for recombination line
Authors and Co-Authors : Nagendra Kumar (IISc, Bangalore), Banibrata Mukhopadhyay (IISc, Bangalore)
Abstract Type : Oral
Abstract Category : Extragalactic Astronomy
Abstract : Wind outflow is inevitable in Low-luminous active galactic nuclei (LLAGNs). X-ray emission of LLAGNs is explained by radiatively-inefficient accretion flow(RIAF, situated in inner region) and its double peaked (red-blue shifted) hydrogen-alpha line reveals a thin accretion disk in outer region. Recently, Sgr A* exhibits a double peaked H30-alpha recombination line, to explain this one needs a 10^4K thin disk ~10^4R_g(R_g: gravitational radius), which is unexpected with very low mass-accretion rate. Thermal irradiation induced wind outflow (is an equatorial wind with small opening angle, is capable to generate double peaked emission/absorption line; Kumar and Mukhopadhyay 2020) can provide a favourable environment for recombination line in windy site. Briefly, the model is applicable in the outer region of the disk, mainly in the gas pressure dominated region. Wind solution is always subsonic, basically sonic point conditions predict that the fluids arrive to the equipartition of energy state (precisely the pressure gradient becomes equal to the gradient of the kinetic energy per unit volume) or to an isobaric regime. It launches from the sonic point when radial component of pressure gradient is comparable to the radial gravitational force otherwise fluids are rotationally bound. We start the accretion flow from the Bondi accretion radius with Bondi mass-accretion rate, compute the variation of mass-accretion rate with radius. With constraint of energetics(supplied Vs requirement), and of outer mass-accretion rate for RIAF, we find that in thin accretion disk,  wind can launch from the radius r >2000R_g and corresponding wind ejection height ranges from 0.1r to 0.2r. Wind density is always 8 orders lesser than disk midplane density and its associated temperature is approx 20 times larger than midplane temperature. Particularly, at a windy site(r ~10^4R_g) wind hydrogen number density is ~10^3cm^{-3} and temperature is >10^4K.