A Tail of Two Clumps

Abstract

We present two axisymmetric simulations of a high velocity clump in a photoionized region: one for the case of a uniform, low density environment and a second one for the case of a clump first traveling within a high density medium and then emerging into a low density environment. We show that the second scenario results in the production of an axial tail of dense material with a linear velocity vs. position ramp (with zero velocity at the high/low density environment transition). This material comes from a confined bow shock (produced by the clump when it was within the dense cloud) that emerges into the low environmental density region.

“Head/Tail Plasmon” Produced by a Gaussian Ejection Velocity Pulse

“…Under the assumption of a cylindrical flow, the position x cm of the center of mass of the material that has entered the working surface at the head of the plasmon (see equation 1 of Raga et al 2020) is given by:…”

“…Following Cantó et al (2000) and Raga et al (2020), instead of inverting equation ( 8), we will use τ (i.e., the ejection time) as independent variable, and find x cm (from equation 6) and the evolutionary time t (from equation 8) as a function of τ . We now consider a Gaussian ejection velocity variability (see equation 4), a constant ejection density ρ 0 and a uniform ambient density ρ a .…”

“…In a recent paper, Raga et al (2020) have presented a model for a "single pulse ejection" jet, which results in the production of a dense "head" joined to the outflow source by a "tail" which develops a linear, Hubble law velocity structure for times greater than the duration of the pulse. This "head/tail plasmon" flow is clearly promising for modelling the objects described above.…”

“…This "head/tail plasmon" flow is clearly promising for modelling the objects described above. Raga et al, (2020) studied the problem of a collimated flow produced by a parabolic, single pulse ejection velocity variability. They also assumed the mass loss rate to be time-independent during the duration of the pulse (so that the ejection density is proportional to the inverse of the ejection velocity).…”

“…In the present paper, we extend the work of Raga et al (2020) to a different functional form for the ejection velocity pulse, which we now assume to have a Gaussian time-dependence. We also study two different forms for the ejection density history: a timeindependent density, and a Gaussian density history (with the same time-width as the velocity pulse).…”