The optical spectra of atomic/ionic mixing layers in outflows from young stars

Details The optical spectra of atomic/ionic mixing layers in outflows from young stars The optical spectra of atomic/ionic mixing layers in outflows from young stars

Jun 1999

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999a%26a...346..260b&link_type=abstract

Astronomy and Astrophysics, v.346, p.260-266 (1999)

Astronomy and Astrophysics

Astrophysics

20

Hydrodynamics, Shock Waves, Stars: Pre-Main Sequence, Stars: Winds, Outflows, Ism: Herbig-Haro Objects, Ism: Jets And Outflows

Scientific paper

It has been previously suggested on kinematical grounds that at least part of the emission from Herbig-Haro (HH) objects might be produced in turbulent mixing layers associated with high velocity outflows. In order to explore this possibility, we compute 1D models of the temperature and ionization cross sections of mixing layers between a high velocity flow and a stationary environment (both the jet beam and the environment being atomic). The mixing layer models are very simple from the dynamical point of view (being based on a ``turbulent viscosity'' approach), but include a detailed treatment of the relevant atomic/ionic processes and radiative cooling for the 8 most important elements (H, He, C, N, O, Ne, S, Fe). In this way, we produce a grid of 1D models with three free parameters: the velocity of the jet, the local width of the mixing layer h, and the environment pressure Penv. These models are to some extent comparable to a family of plane-parallel, steady shock models computed for different pre-shock velocities and densities. We find that the temperature cross-section changes from parabolic to flat-topped as the layer width increases, as predicted by earlier analytical results. The ionization fraction does not show this behavior and is always strongly out of coronal equilibrium, because of turbulent diffusion of neutral gas from the jet and external medium into the layer. Above a minimum jet velocity, we find that the predicted temperature and optical spectra of the mixing-layer depend mostly on the combination hPenv/(alpha v_j(2)equiv ) Sigma [where alpha ( =~ 0.007) is the adopted turbulent viscosity parameter and v_j the velocity of the jet]. This contrasts with shock models, where line ratios are strongly dependent upon the shock velocity. The [O I]6300/Hα ratio predicted by mixing-layer models appears too high by a factor of two compared with the line ratios of low-excitation HH objects. However, it may be compatible with line ratios in the intermediate velocity component of T Tauri jets, which have been suggested to trace jet mixing layers.

Affiliated with

Also associated with

No associations

Rating

The optical spectra of atomic/ionic mixing layers in outflows from young stars does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with The optical spectra of atomic/ionic mixing layers in outflows from young stars, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The optical spectra of atomic/ionic mixing layers in outflows from young stars will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1494763