Numerical Simulations of HH 555

We present 3D gasdynamic simulations of the Herbig Haro object HH 555. HH 555 is a bipolar jet emerging from the tip of an elephant trunk entering the Pelican Nebula from the adjacent molecular cloud. Both beams of HH 555 are curved away from the center of the H II region. This indicates that they are being deflected by a side-wind probably coming from a star located inside the nebula or by the expansion of the nebula itself. HH 555 is most likely an irradiated jet emerging from a highly embedded protostar, which has not yet been detected. In our simulations we vary the incident photon flux, which in one of our models is equal to the flux coming from a star 1 pc away emitting 5x10^48 ionizing (i. e., with energies above the H Lyman limit) photons per second. An external, plane-parallel flow (a ``side-wind'') is coming from the same direction as the photoionizing flux. We have made four simulations, decreasing the photon flux by a factor of 10 in each simulation. We discuss the properties of the flow and we compute Halpha emission maps (integrated along lines of sight). We show that the level of the incident photon flux has an important influence on the shape and visibility of the jet. If the flux is very high, it causes a strong evaporation of the neutral clump, producing a photoevaporated wind traveling in the direction opposite to the incident flow. The interaction of the two flows creates a double shock ``working surface'' around the clump protecting it and the jet from the external flow. The jet only starts to curve when it penetrates through the working surface.Comment: 14 pages, 4 figures, accepted by Ap

A latitude-dependent wind model for Mira's cometary head

We present a 3D numerical simulation of the recently discovered cometary structure produced as Mira travels through the galactic ISM. In our simulation, we consider that Mira ejects a steady, latitude-dependent wind, which interacts with a homogeneous, streaming environment. The axisymmetry of the problem is broken by the lack of alignment between the direction of the relative motion of the environment and the polar axis of the latitude-dependent wind. With this model, we are able to produce a cometary head with a ``double bow shock'' which agrees well with the structure of the head of Mira's comet. We therefore conclude that a time-dependence in the ejected wind is not required for reproducing the observed double bow shock.Comment: 4 pages, 4 figures, accepted for publication in ApJ

The 3-Dimensional Structure of HH 32 from GMOS IFU Spetroscopy

We present new high resolution spectroscopic observations of the Herbig-Haro object HH 32 from System Verification observations made with the GMOS IFU at Gemini North Observatory. The 3D spectral data covers a 8''.7 x 5''.85 spatial field and 4820 - 7040 Angstrom spectral region centered on the HH~32 A knot complex. We show the position-dependent line profiles and radial velocity channel maps of the Halpha line, as well as line ratio velocity channel maps of [OIII]5007/Halpha, [OI]6300/Halpha, [NII]6583/Halpha, [SII](6716+6730)/Halpha and [SII]6716/6730. We find that the line emission and the line ratios vary significantly on spatial scales of ~1'' and over velocities of ~50 km/s. A ``3/2-D'' bow shock model is qualitatively successful at reproducing the general features of the radial velocity channel maps, but it does not show the same complexity as the data and it fails to reproduce the line ratios in our high spatial resolution maps. The observations of HH 32 A show two or three superimposed bow shocks with separations of ~3'', which we interpret as evidence of a line of sight superposition of two or three working surfaces located along the redshifted body of the HH 32 outflow.Comment: Accepted for Publication in the Astronomical Journal (January 2004

A model of Mira's cometary head/tail entering the Local Bubble

We model the cometary structure around Mira as the interaction of an AGB wind from Mira A, and a streaming environment. Our simulations introduce the following new element: we assume that after 200 kyr of evolution in a dense environment Mira entered the Local Bubble (low density coronal gas). As Mira enters the bubble, the head of the comet expands quite rapidly, while the tail remains well collimated for a 100 kyr timescale. The result is a broad-head/narrow-tail structure that resembles the observed morphology of Mira's comet. The simulations were carried out with our new adaptive grid code WALICXE, which is described in detail.Comment: 12 pages, 8 figures (4 in color). Accepted for publication in The Astrophysical Journa

A 3-mode, Variable Velocity Jet Model for HH 34

Variable ejection velocity jet models can qualitatively explain the appearance of successive working surfaces in Herbig-Haro (HH) jets. This paper presents an attempt to explore which features of the HH-34 jet can indeed be reproduced by such a model. From previously published data on this object, we find evidence for the existence of a 3-mode ejection velocity variability, and then explore the implications of such a variability. From simple, analytic considerations it is possible to show that the longer period modes produce a modulation on the shorter period modes, resulting in the formation of ``trains'' of multiple knots. The knots observed close to the source of HH-34 could correspond to such a structure. Finally, a numerical simulation with the ejection velocity variability deduced from the HH-34 data is computed. This numerical simulation shows a quite remarkable resemblance with the observed properties of the HH-34 jet.Comment: 28 pages LaTex, 10 postscript figure

Emission lines from rotating proto-stellar jets with variable velocity profiles. I. Three-dimensional numerical simulation of the non-magnetic case

Using the Yguazu-a three-dimensional hydrodynamic code, we have computed a set of numerical simulations of heavy, supersonic, radiatively cooling jets including variabilities in both the ejection direction (precession) and the jet velocity (intermittence). In order to investigate the effects of jet rotation on the shape of the line profiles, we also introduce an initial toroidal rotation velocity profile, in agreement with some recent observational evidence found in jets from T Tauri stars which seems to support the presence of a rotation velocity pattern inside the jet beam, near the jet production region. Since the Yguazu-a code includes an atomic/ionic network, we are able to compute the emission coefficients for several emission lines, and we generate line profiles for the H, [O I]6300, [S II]6716 and [N II]6548 lines. Using initial parameters that are suitable for the DG Tau microjet, we show that the computed radial velocity shift for the medium-velocity component of the line profile as a function of distance from the jet axis is strikingly similar for rotating and non-rotating jet models. These findings lead us to put forward some caveats on the interpretation of the observed radial velocity distribution from a few outflows from young stellar objects, and we claim that these data should not be directly used as a doubtless confirmation of the magnetocentrifugal wind acceleration models.Comment: 15 pages, 8 figures. Accepted to publication in Astronomy and Astrophysic

Polarization Profiles of Scattered Emission Lines. II. Upstream Dust Scattering in the HH 1 Jet

Detailed comparisons are made between observations of scattered light upstream of the head of the HH~1 jet and predictions of simple scattering models. It is shown that, in order to unambiguously determine the velocity of the head of the jet (bow shock) with respect to the upstream dust, existing spectroscopic observations are insufficient and that spectropolarimetric observations of the scattered light are necessary. Such an independent measure of the bow shock velocity is important in order to test ``multiple outflow'' theories of Herbig-Haro jets. It is also shown 2that the scattering dust must have a very forward-throwing scattering phase function (\langle\cos\theta\rangle\msim 0.7) and slight evidence is found for a dust-gas ratio that is higher than average.Comment: 11 pages, uuencoded compressed postscript (including 9 figures), accepted for publication in Ap.J., IAUNAM_contrib.#34

Jet-cloud interations and the brightening of the narrow line region in Seyfert galaxies

We study the kinematical and brightness evolution of emission line clouds in the narrow line region (NLR) of Seyfert galaxies during the passage of a jet. We derive a critical density above which a cloud remains radiative after compression by the jet cocoon. The critical density depends mainly on the cocoon pressure. Super-critical clouds increase in emission line brightness, while sub-critical clouds generally are highly overheated reducing their luminosity below that of the inter-cloud medium. Due to the pressure stratification in the bow-shock of the jet, a cylindrical structure of nested shells develops around the jet. The most compact and brightest compressed clouds surround the cloud-free channel of the radio jet. To support our analytical model we present a numerical simulation of a supersonic jet propagating into a clumpy NLR. The position-velocity diagram of the simulated H_alpha emission shows total line widths of the order of 500 km/s with large-scale variations in the radial velocities of the clouds due to the stratified pressure in the bow-shock region of the jet. Most of the luminosity is concentrated in a few dense clouds surrounding the jet. These morphological and kinematic signatures are all found in the well observed NLR of NGC1068 and other Seyfert galaxies.Comment: 11 pages, 3 figures, accepted for publication in The Astrophysical Journal Letter