The Precession of the Giant HH 34 Outflow: A Possible Jet Deceleration Mechanism (original) (raw)

3D sph simulations of giant herbig-haro flows and jet-cloud interactions in star formation regions

RevMexAA (Serie de …, 2000

Describimos algunos resultados recientes de simulaciones tridimensionales con hidrodinámica de partículas suavizadas (SPH) de chorros densos con enfriamiento radiativo en regiones de formación estelar. Discutimos la estructura y cinemática de los objetos HH gigantes recientemente detectados y la interacción de chorros HH con las nubes densas y compactas que los rodean.

A Variable-Velocity, Precessing Jet Model for HH 32

Astronomical Journal, 2004

HH 32 has a bright, strongly redshifted lobe with a system of scattered condensations. We propose that these condensations correspond to internal working surfaces in a variable ejection velocity, precessing jet. From a three-dimensional numerical simulation, we obtain predictions of

Infall and Outflow around the HH 212 Protostellar System

The Astrophysical Journal, 2006

HH 212 is a highly collimated jet discovered in H 2 powered by a young Class 0 source, IRAS 05413-0104, in the L1630 cloud of Orion. We have mapped around it in 1.33 mm continuum, 12 CO (J = 2 − 1), 13 CO (J = 2 − 1), C 18 O (J = 2 − 1), and SO (J K = 6 5 − 5 4 ) emission at ∼ 2.5 ′′ resolution with the Submillimeter Array. A dust core is seen in the continuum around the source. A flattened envelope is seen in C 18 O around the source in the equator perpendicular to the jet axis, with its inner part seen in 13 CO. The structure and kinematics of the envelope can be roughly reproduced by a simple edge-on disk model with both infall and rotation. In this model, the density of the disk is assumed to have a power-law index of p = −1.5 or −2, as found in other low-mass envelopes. The envelope seems dynamically infalling toward the source with slow rotation because the kinematics is found to be roughly consistent with a free fall toward the source plus a rotation of a constant specific angular momentum. A 12 CO outflow is seen surrounding the H 2 jet, with a narrow waist around the source. Jetlike structures are also seen in 12 CO near the source aligned with the H 2 jet at high velocities. The morphological relationship between the H 2 jet and the 12 CO outflow, and the kinematics of the 12 CO outflow along the jet axis are both consistent with those seen in a jet-driven bow shock model. SO emission is seen around the source and the H 2 knotty shocks in the south, tracing shocked emission around them.

New Variable Jet Models for HH 34

The Astrophysical Journal, 2011

We consider newly derived proper motions of the HH 34 jet to reconstruct the evolution of this outflow. We first extrapolate ballistic trajectories for the knots (starting from their present-day positions and velocities) and find that at ∼1000 yr in the future most of them will merge to form a larger-mass structure. This mass structure will be formed close to the present-day position of the HH 34S bow shock. We then carry out a fit to the ejection velocity versus time reconstructed from the observed proper motions (assuming that the past motion of the knots was ballistic) and use this fit to compute axisymmetric jet simulations. We find that the intensity maps predicted from these simulations do indeed match reasonably well the [S ii] structure of HH 34 observed in Hubble Space Telescope images.

Astrophysical jets: insights into long-term hydrodynamics

New Journal of Physics, 2011

Astrophysical jets are ubiquitous throughout the universe. They can be observed to emerge from protostellar objects, stellar x-ray binaries and supermassive black holes located at the center of active galaxies, and they are believed to originate from a central object that is surrounded by a magnetized accretion disc. With the motivations to understand whether hypersonic Newtonian jets produce any similarity to the morphologies observed in jets from young stellar objects (YSOs) and whether numerical codes, based on Godunov-type schemes, capture the basic physics of shocked flows, we have conceived a laboratory experiment and performed three-dimensional (3D) numerical simulations that reproduce the mid-to-long-term evolution of hypersonic jets. Here we show that these jets propagate, maintaining their collimation over long distances, in units of the jet initial radius. The jets studied are quasi-isentropic, are both lighter and heavier than the ambient and meet the two main scaling parameter requirements for proto-stellar jets: the ejection Mach number and the ambient/jet density ratio.

Astrophysical jets and outflows

Advances in Space Research, 2005

Highly collimated supersonic jets and less collimated outflows are observed to emerge from a wide variety of astrophysical objects. They are seen in young stellar objects (YSOs), proto-planetary nebulae, compact objects (like galactic black holes or microquasars, and X-ray binary stars), and in the nuclei of active galaxies (AGNs). Despite their different physical scales (in size, velocity, and amount of energy transported), they have strong morphological similarities. What physics do they share? These systems are either hydrodynamic or magnetohydrodynamic (MHD) in nature and are, as such, governed by non-linear equations. While theoretical models helped us to understand the basic physics of these objects, numerical simulations have been allowing us to go beyond the one-dimensional, steady-state approach extracting vital information. In this lecture, the formation, structure, and evolution of the jets are reviewed with the help of observational information, MHD and purely hydrodynamical modeling, and numerical simulations. Possible applications of the models particularly to YSOs and AGN jets are addressed. 1 1 pc = 1 parsec = 3.086 10 18 cm. 2 1 M = one solar mass = 1.99 10 33 g 3 1 L = one solar luminosity unit = 3.826 10 33 erg/s

The Deceleration of Giant Herbig‐Haro Flows

The Astrophysical Journal, 2001

It has been recently discovered that spatially separated Herbig-Haro objects, once considered unrelated, are linked within a chain that may extend for parsecs in either direction of the embedded protostar forming a giant Herbig-Haro jet.

An Episodic Wide-angle Outflow in HH 46/47

The Astrophysical Journal, 2019

During star formation, the accretion disk drives fast MHD winds, which usually contain two components, a collimated jet and a radially distributed wide-angle wind. These winds entrain the surrounding ambient gas producing molecular outflows. We report a recent observation of 12CO (2–1) emission of the HH 46/47 molecular outflow by the Atacama Large Millimeter/submillimeter Array, in which we identify multiple wide-angle outflowing shell structures in both the blueshifted and redshifted outflow lobes. These shells are highly coherent in position–position–velocity space, extending to ≳40–50 km s−1 in velocity and 104 au in space, with well-defined morphology and kinematics. We suggest these outflowing shells are the result of the entrainment of ambient gas by a series of outbursts from an intermittent wide-angle wind. Episodic outbursts in collimated jets are commonly observed, yet detection of a similar behavior in wide-angle winds has been elusive. Here we show clear evidence that t...

Two-component jet simulations. II. Combining analytical disk and stellar MHD outflow solutions

Astronomy & Astrophysics, 2009

Context. Theoretical arguments along with observational data of YSO jets suggest the presence of two steady components: a disk wind type outflow needed to explain the observed high mass loss rates and a stellar wind type outflow probably accounting for the observed stellar spin down. Each component's contribution depends on the intrinsic physical properties of the YSO-disk system and its evolutionary stage. Aims. The main goal of this paper is to understand some of the basic features of the evolution, interaction and co-existence of the two jet components over a parameter space and when time variability is enforced. Methods. Having studied separately the numerical evolution of each type of the complementary disk and stellar analytical wind solutions in Paper I of this series, we proceed here to mix together the two models inside the computational box. The evolution in time is performed with the PLUTO code, investigating the dynamics of the two-component jets, the modifications each solution undergoes and the potential steady state reached. Results. The co-evolution of the two components, indeed, results in final steady state configurations with the disk wind effectively collimating the inner stellar component. The final outcome stays close to the initial solutions, supporting the validity of the analytical studies. Moreover, a weak shock forms, disconnecting the launching region of both outflows with the propagation domain of the twocomponent jet. On the other hand, several cases are being investigated to identify the role of each two-component jet parameter. Time variability is not found to considerably affect the dynamics, thus making all the conclusions robust. However, the flow fluctuations generate shocks, whose large scale structures have a strong resemblance to observed YSO jet knots. Conclusions. Analytical disk and stellar solutions, even sub modified fast ones, provide a solid foundation to construct twocomponent jet models. Tuning their physical properties along with the two-component jet parameters allows a broad class of realistic scenarios to be addressed. The applied flow variability provides very promising perspectives for the comparison of the models with observations.

An investigation of the hydrodynamics of hypersonic jets in astrophysical conditions

EAS Publications Series, 2012

Hypersonic, collimated jets are being lately intensively studied in Earth laboratories, trying to reproduce some of the physical properties of a subclass of astrophysical jets that are the Herbig-Haro (HH) jets. These jets are produced in the regions around Young Stellar Objects (YSOs), that are proto-stars located inside galactic Giant Molecular Clouds. In addition to the novel experimental approach, HH or YSO jets have been object of interest by the astrophysical community since a few decades and studied by means of observations at different wavelengths and analytical and numerical modeling. We present laboratory experiments and 2D numerical simulations of hypersonic jets, comparing the results of experiments and simulations that reproduce the evolution of the above mentioned jets. The experimental flows match two main scaling parameter requirements for proto-stellar jets, i.e. the ejection Mach number M and the jet/ambient density ratio η. In particular, η goes from slightly underdense to overdense values. Furthermore, as a development of previous works, we consider here the dependence of the jet structure and morphology on the Mach number, in the range 10 to 15.