Supernovae and AGN driven galactic outflows. (arXiv:1209.0242v1 [astro-ph.CO])

Supernovae and AGN driven galactic outflows. (arXiv:1209.0242v1 [astro-ph.CO]):
We present analytical solutions for winds from galaxies with NFW dark matter
halo. We consider winds driven by energy and mass injection from multiple
supernovae, as well as momentum injection due to radiation from a central black
hole. We find that the wind dynamics depends on three velocity scales: (a)
v_star \sim (\dot{E} / 2 \dot{M})^{1/2} describes the effect of starburst
activity, with \dot{E}, \dot{M} as energy and mass injection rate in a central
region of radius R; (b) \vbh ~ (G\mbh / 2 R)^{1/2} for the effect of a central
black hole of mass \mbh on gas at distance R and (c) v_{s} =(GM_h/ 2Cr_s)^{1/2}
which is closely related to the virial velocity, with C as a function of halo
concentration parameter. We find the wind terminal speed to be 2 (v_star^2
+1.5(\Gamma -1) \vbh^2 -v_s^2)^{1/2}, where \Gamma is the ratio of force due to
radiation pressure to gravity of the central black hole. We also find that: (a)
winds from quiescent star forming galaxies cannot escape from 10^{11.5} \le M_h
\le 10^{12.5}Msun galaxies, (b) circumgalactic gas at large distances should be
present for galaxies in this mass range, (c) for an escaping wind, the wind
speed in low to intermediate mass galaxies is ~ 400--1000 km/s, consistent with
observed X-ray temperatures; (d) winds from massive galaxies with AGN have
speeds \gtrsim 1000 km/s. We also find that the ratio [2 v_star ^2 -(1 -\Gamma)
\vbh^2]/ \vvir^2 dictates the amount of gas lost. Used in conjunction with an
appropriate relation between \mbh and M_h, and an appropriate opacity of dust
grains in IR (K band), this ratio becomes minimum at a certain halo mass scale
(M_h ~ 10^{12--12.5} Msun) that signifies the cross-over of AGN domination in
outflow properties from starburst activity at lower masses. We find that
stellar mass for massive galaxies scales as M_star \propto M_h^{0.26},and for
low mass galaxies, M_star \propto M_h^{5/3}.