Heating and Ionization of X-Winds

H. Shang; A. E. Glassgold; F. H. Shu; S. Lizano

doi:10.1086/324197

paper

Heating and Ionization of X-Winds

arXiv:astro-ph/0110539 · doi:10.1086/324197

Abstract

In order to compare the x-wind with observations, one needs to be able to calculate its thermal and ionization properties. We formulate the physical basis for the streamline-by-streamline integration of the ionization and heat equations of the steady x-wind. In addition to the well-known processes associated with the interaction of stellar and accretion-funnel hot-spot radiation with the wind, we include X-ray heating and ionization, mechanical heating, and a revised calculation of ambipolar diffusion heating. The mechanical heating arises from fluctuations produced by star-disk interactions of the time dependent x-wind that are carried by the wind to large distances where they are dissipated in shocks, MHD waves, and turbulent cascades. We model the time-averaged heating by the scale-free volumetric heating rate, $Γ_{mech} = α ρ v^{3} s^{- 1}$ , where $ρ$ and $v$ are the local mass density and wind speed, respectively, $s$ is the distance from the origin, and $α$ is a phenomenological constant. When we consider a partially-revealed but active young stellar object, we find that choosing $α \sim 1 0^{- 3}$ in our numerical calculations produces temperatures and electron fractions that are high enough for the x-wind jet to radiate in the optical forbidden lines at the level and on the spatial scales that are observed. We also discuss a variety of applications of our thermal-chemical calculations that can lead to further observational checks of x-wind theory.

48 pages, 5 figures, ApJ in press. For better figures, go to http://www.asiss.sinica.edu.tw/theory/prints.html

Heating and Ionization of X-Winds

Abstract

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