Jet-like Structure Research Articles

Three-dimensional hydrodynamical modeling of mass transfer in the close binary system β Lyr

We present a three-dimensional hydrodynamical modeling of mass transfer in the close binary system β Lyr taking radiative cooling into account explicitly. The assumed mass-transfer rate through the first Lagrangian point L1 is 3.0 × 10−5M⊙/yr. A flow with a radius of 0.14–0.16 (in units of orbital separation) is formed in the vicinity of L1. This flow forms an accretion disk with a radius close to 23 R⊙ and a thickness of about 10 R⊙. The accretion disk is surrounded by an outer envelope that extends beyond the computational domain. A spiral shock forms at the outer boundary of the disk at orbital phase 0.25. Geometrically, the disk is toruslike, while the outer envelope is cylinder-like. In this model, which has low temperatures inside the computational domain, no jetlike structures form in the disk. It is possible that the jetlike structure in β Lyr arises due to the interaction of radiative wind from the accretor with the flow from L1. In the model considered, a hot region exists over the poles of the accretor at a height of about 0.21. The amount of matter lost by the system is close to 10% of the mass flowing through L1; i.e., the mass transfer in the system is almost conservative. For a mass-transfer rate of 3.0 × 10−5M⊙/yr, the orbital period varies by 40.4 s/yr. This means that the observed variation of the orbital period of 19 s/yr should correspond to a mass-transfer rate close to 1.0 × 10−5M⊙/yr.

Three-dimensional hydrodynamical modeling of mass transfer in the close binary system β Lyr with an accretor wind

We present three-dimensional hydrodynamical modeling of mass transfer in the close binary system β Lyr taking into account explicitly radiative cooling and the stellar wind of the accretor. Our computations show that flow forces wind out from the orbital plane, where an accretion disk with a radius of 0.4–0.5 and a height of about 0.15–0.17 (in units of orbital separation) is formed. Gas motions directed upward from the orbital plane are initiated in the region of interaction of the flow from L1 and the accretor wind (x = 0.91, y = −0.17); i.e., a jetlike structure forms. This structure has the shape of a gas pillar above the orbital plane, where gas moves with the velocity of stellar wind. The number density of the gas in this structure is about 1014 cm−3, and its temperature is 20 000–45 000 K. At heights of about 0.15–0.20 above the orbital plane, in the region between the jetlike structure and the disk, two spiral shocks form. It is possible that the emission lines observed in the spectrum of β Lyr binary originate in this region.

Outflows, Disks, and Stellar Content in a Region of High‐Mass Star Formation: G5.89−0.39 with Adaptive Optics

We present adaptive optics (AO)-assisted near-infrared Fabry-Perot observations of both the H2 v=1-0 S(1) line in the area surrounding the shell-like ultracompact H II region (UCH II) G5.89-0.39 and the Brγ emission in the region of ionized gas. This work aims at investigating the near-IR counterpart to the widely debated massive outflow detected toward this source. We also study the connection of the outflow(s) with the possible driving source(s) to better constrain the stellar content within this UCH II region. Our data show evidence of a total of three outflows in this region, with distinct orientations and different driving sources. Two prominent bow-shock structures are identified in our H2 data in a north-south orientation. The molecular jet, likely associated with these features, is not compatible with the orientation of the outflow previously detected at high spatial resolution in SiO emission. Moreover, we propose the driving source of this jetlike structure as the O5 V star recently detected by Feldt and coworkers. However, we report the detection of a bipolar structure, separated by a dark lane, at the location of the 1.3 mm continuum source (i.e., the candidate source to power the SiO outflow). Finally, a third bipolar outflow is traced through the Brγ emission. The confirmation through CO interferometric observations of this outflow activity would therefore favor an accretion scenario for high-mass star formation. Based on observations made with ESO Telescopes at La Silla and Paranal under programs ID:64.I-0532 and ID:73.C-0178. Based on observations collected at the Centro Astronomico Hispano Aleman (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut fur Astronomie and the Instituto de Astrofisica de Andalucia (CSIC).

Infall and Outflow around the HH 212 Protostellar System

HH 212 is a highly collimated jet discovered in H2 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, 12CO ($J=2-1$), 13CO ($J=2-1$), C18O ($J=2-1$), and SO ($J_K = 6_5-5_4$) emission at $\sim$ \arcs{2.5} resolution with the Submillimeter Array. A dust core is seen in the continuum around the source. A flattened envelope is seen in C18O around the source in the equator perpendicular to the jet axis, with its inner part seen in 13CO. 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 12CO outflow is seen surrounding the H2 jet, with a narrow waist around the source. Jetlike structures are also seen in 12CO near the source aligned with the H2 jet at high velocities. The morphological relationship between the H2 jet and the 12CO outflow, and the kinematics of the 12CO 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 H2 knotty shocks in the south, tracing shocked emission around them.

Laminar flow of a viscoelastic shear-thinning liquid through a plane sudden expansion preceded by a gradual contraction

Experimental observations are reported for the laminar flow of a viscoelastic liquid through a symmetrical plane sudden expansion preceded by a gradual contraction from a square duct. As is well known, for Newtonian fluid flow above a critical Reynolds number the flowfield downstream of an expansion becomes asymmetric. For the viscoelastic liquid investigated here the asymmetry is greatly reduced, with very similar reattachment lengths for the two recirculation regions. More significantly, the flow unexpectedly develops a strongly three-dimensional jet-like structure, with side-to-side symmetry centred on the ‘vertical’ symmetry plane of the contraction/expansion geometry. Especially interesting is the flow within the contraction itself, where the nature of the flow field for the viscoelastic liquid is also fundamentally different to that for a comparable Newtonian fluid flow: large velocity overshoots with very strong gradients occur near to the sidewalls that, due to their appearance, we have termed ‘cat's ears’. The fully developed approach flow in the square duct is unremarkable.

A Narrow Band Chandra X-ray Analysis of SNR 3C 391

We present narrow-band and equivalent width (EW) images of the thermal composite supernova remnant (SNR) 3C 391 in the X-ray emission lines of Mg, Si and S using the Chandra ACIS Observational data. The EW images reveal the spatial distribution of the emission of the metal species Mg, Si and S in the remnant. They have a clumpy structure similar to that seen in the broadband diffuse emission, suggesting that they are largely of interstellar origin. We find an interesting finger-like feature protruding outside the southwestern radio border of the remnant, somewhat similar to the jet-like Si structure found in the famous SNR Cas A. This feature may possibly be the debris of the jet of ejecta from an asymmetrical supernova explosion of a massive progenitor star.

The Circumstellar Environment of T Tauri S at High Spatial and Spectral Resolution

We have obtained the first high spatial (0.05) and spectral (R~35,000) resolution 2 μm spectrum of the T Tau S tight binary system using adaptive optics on the Keck II telescope. We have also obtained the first 3.8 and 4.7 μm images that resolve the three components of the T Tau multiple system, as well as new 1.6 and 2.2 μm images. Together with its very red near-infrared colors, the spectrum of T Tau Sb shows that this T Tauri star is extincted by a roughly constant extinction of AV~15 mag, which is probably the 0.7×0.5 circumbinary structure recently observed in absorption in the ultraviolet. T Tau Sa, which is also observed through this screen and is actively accreting, further possesses a small edge-on disk that is evidenced by warm (390 K), narrow overtone CO rovibrational absorption features in our spectrum. We find that T Tau Sa is most likely an intermediate-mass star surrounded by a semitransparent 2-3 AU radius disk whose asymmetries and short Keplerian rotation explain the large photometric variability of the source on relatively short timescales. We also show that molecular hydrogen emission exclusively arises from the gas that surrounds T Tau S and that its spatial and kinematic structure, while providing suggestive evidence of a jetlike structure, is highly complex.

OH 12.8-0.9: A New Water-Fountain Source

We present observational evidence that the OH/IR star OH 12.8-0.9 is the fourth in a class of objects previously dubbed sources. Using the Very Long Baseline Array, we produced the first images of the H2O maser emission associated with OH 12.8-0.9. We find that the masers are located in two compact regions with an angular separation of ~109 mas on the sky. The axis of separation between the two maser regions is at a position angle of 15 east of north, with the blueshifted (-80.5 to -85.5 km s-1) masers located to the north and the redshifted (-32.0 to -35.5 km s-1) masers to the south. In addition, we find that the blue- and redshifted masers are distributed along arclike structures ~10-12 mas across, oriented roughly perpendicular to the separation axis. The morphology exhibited by the H2O masers is suggestive of an axisymmetric wind with the masers tracing bow shocks formed as the wind impacts the ambient medium. This bipolar jet-like structure is typical of the three other confirmed water-fountain sources. When combined with the previously observed spectral characteristics of OH 12.8-0.9, the observed spatiokinematic structure of the H2O masers provides strong evidence that OH 12.8-0.9 is indeed a member of the water-fountain class.

A Chandra Survey of Quasar Jets: First Results

We present results from Chandra X-ray imaging and spectroscopy of a flux-limited sample of flat-spectrum radio-emitting quasars with jetlike extended structure. Twelve of 20 quasar jets are detected in 5 ks ACIS-S exposures. The quasars without X-ray jets are not significantly different from those in the sample with detected jets except that the extended radio emission is generally fainter. New radio maps are combined with the X-ray images in order to elucidate the relation between radio and X-ray emission in spatially resolved structures. We find a variety of morphologies, including long straight jets and bends up to 90°. All X-ray jets are one-sided although the radio images used for source selection often show lobes opposite the X-ray jets. The FR II X-ray jets can all be interpreted as inverse Compton scattering of cosmic microwave background photons by electrons in large-scale relativistic jets although deeper observations are required to test this interpretation in detail. Applying this interpretation to the jets as a population, we find that the jets would be aligned to within 30° of the line of sight generally, assuming that the bulk Lorentz factor of the jets is 10.

Accelerated electron populations formed by Langmuir wave-caviton interactions

Direct numerical simulations of electron dynamics in externally driven electrostatic waves have been carried out using a relativistic two-fluid one-dimensional Vlasov–Poisson code. When the driver wave has sufficiently large amplitude, ion density holes (cavitons) form. The interaction between these cavitons and other incoming Langmuir waves gives rise to substantial local acceleration of groups of electrons, and fine jetlike structures arise in electron phase space. We show that these jets are caused by wave breaking when finite amplitude Langmuir waves experience the ion density gradient at the leading edge of the holes, and are not caused by caviton burnout. An analytical two-fluid model gives the critical density gradient and caviton depth for which this process can occur. In particular, the density gradient critically affects the rate at which a Langmuir wave, moving into the caviton, undergoes Landau damping. This treatment also enables us to derive analytical estimates for the maximum energy of accelerated electrons, and for the energy spectrum along a phase-space jet. These are confirmed by direct numerical simulations.

Track formation and electron emission in swift ion collisions with condensed matter

Electron ejection from target atoms is one of the basic processes when ionizing radiation interacts with matter. The primary electrons and their subsequent secondary interactions lead to the deposition of energy around the ion trajectory. The detailed knowledge of the structure of these ion tracks is a key issue for our understanding of radiation effects in condensed matter, an important example being calculations of the RBE of heavy particles, where doubly differential electron ejection cross sections are a key input parameter. Usually, data obtained from single collisions, i.e. with gas targets, are used, but condensed matter effects may considerably alter the emission patterns. Therefore, we will focus on the primary ionization (binary encounter and soft electron emission), which is common to single atoms (gas targets) and condensed matter. Then, special emphasis will be given to discuss effects, which are only seen in condensed matter (electron transport and multiple scattering effects, jet-like structures, wake effects due to collective excitation of plasmons), but not in gaseous targets (single collisions).

Ionized gas and stars in the central kiloparsec of the type 2 Seyfert galaxy NGC 2110 - I. The data

In this paper, we present new results from an extensive set of Hubble Space Telescope (HST) and ground-based observations of the Seyfert galaxy NGC 2110. The HST data sets include Wide Field Planetary Camera 2 (WFPC2) observations as well as the first high-spatial resolution spectroscopy ([O i], [N ii], Hα and [S ii] lines) of this galaxy obtained using the Space Telescope Imaging Spectrograph (STIS). The ground-based data are three-dimensional (x, y, λ) spectrographic observations obtained using the integral field spectrograph OASIS on the Canada–France–Hawaii Telescope, complemented by near-infrared long-slit spectroscopy obtained using NIRSPEC on the Keck–II telescope. The OASIS observations cover regions containing both stellar absorption lines and major optical emission lines. The NIRSPEC observations cover the H and K bands. Combined with archival HST observations, the WFPC2 data provide us with a high-spatial resolution extinction map. The OASIS data allowed bidimensional mapping of the stellar and gaseous kinematics, as well as of the spectral properties of the ionized gas. These results are compared to those obtained in the near-infrared with NIRSPEC/Keck. Last, we used the STIS data to probe the ionized gas kinematics and properties in the inner 4 arcsec along PA = 156° at unprecedented spatial resolution. Our two-dimensional (2D) map of the stellar velocity field and the near-infrared stellar velocity profile are symmetric about the nucleus, confirming the results of previous long-slit observations. The asymmetry of the velocity field of the ionized gas is present at the same level for visible and near-infrared lines, indicating this is not a reddening effect. Multiple Gaussian fitting of the emission-line profile allowed the contributions of the broad and a narrow components to be disentangled. The intensity peak of the [O iii] narrow component is located north of the nucleus, indicating that the bulk of the narrow [O iii] emission comes from the jet-like structure (Mulchaey et al.) and not from the nucleus itself. We suggest that the northern arm is the anomalous one, contrary to what has been claimed earlier. Last, we also show that the elongated region of high gas velocity dispersion located close to the nucleus and discovered by Gonzalez Delgado et al. is intrinsic to the narrow component.

Mean and eddy motion in the Skagerrak/northern North Sea: insight from a numerical model

Insight regarding the mean and eddy motion in the Skagerrak/northern North Sea area is gained through an analysis of model-simulated currents, hydrography, kinetic energy and relative vorticity for the 2 years 2000 and 2001. In this a σ-coordinate ocean model is used. Since the tidal currents are generally strong in the area, care is exercised to distinguish the mesoscale (eddy) motion from higher-frequency motion such as tides, before computing the mean and eddy kinetic energy. The model-simulated response is first compared with available knowledge of the circulation in the area, and when available, also with sea-surface temperature obtained from satellite imagery. It is concluded that the model appears to faithfully reproduce most of what is known, in particularly the upper mixed layer circulation. An analysis of the mean and eddy kinetic energy reveals that many of the mesoscale structures found in the area are recurrent. This is particularly true for the structures off the southern tip of Norway. Also in general, areas of strong mean and eddy kinetic energy are co-located. The exception is the area off the southern tip of Norway, where the eddy kinetic energy is much larger than its mean counterpart. An analysis of the relative vorticity reveals that the variability found is due to the occurrence of recurrent anticyclonic eddies. It is hypothesized that these eddies are generated due to an offshore veering of the Norwegian coastal current (NCC) as it reaches the eastern end of the Norwegian Trench plateau. Here it becomes a free jet, which is then vulnerable to either barotropic instability caused by the horizontal shear in the jet-like structure of the NCC at this point, or a baroclinic (frontal) instability. The latter may come into play when the NCC veers offshore and its relatively fresh water meets the inflowing saline water of Atlantic origin, a frontogenesis that may become strong enough for cyclogenesis to take place. Due to the depth-independent nature of the model-generated eddies, the barotropic instability is the most likely candidate. It remains to resolve the reason for the offshore veering of the NCC. The most likely candidate mechanisms are vortex squeezing or simply that the coastline curvature is large enough for the NCC to separate from the coast in a hydraulic sense.

Discovery of a Jetlike Structure at the High-Redshift QSO CXOMP J084128.3+131107

The Chandra Multiwavelength Project has discovered a jetlike structure associated with a newly recognized QSO at redshift z = 1.866. The system was 94 off-axis during an observation of 3C 207. Although significantly distorted by the mirror point-spread function, we use both a ray trace and a nearby bright point source to show that the X-ray image must arise from some combination of point and extended sources, or else from a minimum of three distinct point sources. We favor the former situation, as three unrelated sources would have a small probability of occurring by chance in such a close alignment. We show that interpretation as a jet emitting X-rays via inverse Compton scattering on the cosmic microwave background is plausible. This would be a surprising and unique discovery of a radio-quiet QSO with an X-ray jet, since we have obtained upper limits of 100 μJy on the QSO emission at 8.46 GHz and limits of 200 μJy for emission from the putative jet.

Vortex dynamics around a solid ripple in an oscillatory flow

We investigate the time-dependent flow of water around a solid triangular profile oscillating horizontally in a narrow rectangular container. The flow is quasi two-dimensional and using particle image velocimetry we measure 20 snapshots of the entire velocity field during a period of oscillation. From the velocity measurements we obtain the circulation of the vortices and study the vortex dynamics. The time-dependence of the flow gives rise to the formation of a jet-like flow structure which enhances the vorticity production compared to the time-independent case. We introduce a simple phenomenological model to describe the important dynamical parameters of the flow, i.e., the vortex circulation and the jet velocity. We solve the model analytically without viscous damping and find good agreement between the model predictions and our measurements. Our work adds to the recent effort to understand more complicated flows past sand-ripples and insect wings.

Dispersal forcing of southern California river plumes, based on field and remote sensing observations

River plumes are important pathways of ter- restrial materials entering the sea. In southern Califor- nia, rivers are known to be the dominant source of littoral, shelf and basin sediment and coastal pollution, although a basic understanding of the dynamics of these river inputs does not exist. Here we evaluate forcing parameters of a southern California river plume using ship-based hydrographic surveys and satellite remote sensing measurements to provide the first insights of river dispersal dynamics in southern California. Our results suggest that plumes of the Santa Clara River are strongly influenced by river inertia, producing jet-like structures � 10 km offshore during annual recurrence (� two-year) flood events and � 30 km during excep- tional (� 10-year recurrence) floods. Upwelling-favor- able winds may be strong following stormwater events and can alter dispersal pathways of these plumes. Due to similar runoff relationships and other reported satellite observations, we hypothesize that interia-dominated dispersal may be an important characteristic of the small, mountainous rivers throughout southern California.

Outflows from Young Stars: Theory and Observation

Recent observations have revealed that young stellar objects are associated with jet-like structures and Herbig-Haro objects emitting at wavelengths ranging from optical lines to radio continua. These phenomena are similar in morphologies, and have mostly comparable energetics, dynamics, and kinematics. Probing such phenomena observed at various wavelengths with self-consistent physical and radiative processes arising within an inner disk-wind driven magnetocentrifugally from the circumstellar accretion disk is a challenge for confronting theory and observation of outflows. How such early outflow phase may play a role in forming planetary materials may help solve puzzles posed by meteorites. We will discuss the relevant observations, theoretical foundations for modelling approaches, magnetic structures and dynamical effects, and the connection to the early solar system.

High Energy Activities of Our Galactic Center and Its Environment

The Japanese X-ray satellite Ginga discovered a largely extended hot plasma around the Galactic center (GC). possibly due to a violent explosion in the GC region within the past 10 5 years [K. Koyama, H. Awaki, H. Kunieda, S. Takano and Y. Tawara, Nature 339 (1989), 603]. Subsequently, the first hard X-ray imaging satellite, ASCA found strong 6.4 keV lines associated with the molecular clouds in the GC region [K. Koyama, Y. Maeda, T. Sonobe, T. Takeshima, Y. Tanaka and S. Yamauchi, Publ. Astron. Soc. Jpn. 48 (1996), 249]. The spectrum and morphology are explained by the fluorescent irradiated by strong X-rays (hence: X-ray reflection nebula) from the GC side. Possible scenario of the X-ray reflection nebula is that the Galactic black hole, Sgr A* was X-ray luminous of Lx ∼ 10 3 9 - 4 0 erg s - 1 in the past of ∼ 100-300 years ago Recent Chandra observations on the GC have confirmed these results and furthermore, with its unprecedented spatial resolution, have resolved a number of non-thermal X-ray filaments as well as the 6.4 keV line clouds [H. Murakami, K. Koyama, M. Sakano, M. Tsujimoto and Y. Maeda, Astrophys. J. 534 (2000), 283; H. Murakami, K. Koyama, M. Tsujimoto, Y. Maeda and M. Sakano, Astrophys. J. 550 (2001), 297: H. Murakami, K. Koyama and Y. Maeda. Astrophys. J. 558 (2001), 687; M. Sakano, R. S. Warwick. A. Decourchelle and P. Predehl, Mon. Not. R. Astron. Soc. 340 (2003), 747: Q. D. Wing, E. V. Gotthelf and C. C. Lang, Nature 415 (2002), 148; Q. D. Wang, F. Lu and C. C. Laiig, Astrophys. J. 581 (2002), 1148]. One of the most exciting discoveries is a jet-like Structure emanating near from Sgr A* [A. Bamba, R. Yamazaki, M. Ueno and K. Koyama, Astrophys. J. 589 (2003), 827]. We infer that the Galactic center jets were created some hundreds years ago by sudden mass serge onto the Galactic black hole. This might also be the origin of the X-ray reflection nebula.

The ASCA andChandraObservations of the Galactic Center

This paper reports the new results of the high energy activity found with the X-ray observations of the Galactic center (GC). The Ginga satellite discovered the largely extended hot plasma around the GC, suggesting a violent activity of the GC within 105 year. ASCA found strong 6.4 keV line emissions from the molecular clouds near the GC, which is well explained by the fluorescent caused by strong X-ray irradiations from Sgr A* of ~ 100-300 years ago. Recent Chandra observations on the GC have confirmed these previous results and moreover, with its unprecedented spatial resolution, have resolved a number of non-thermal/6.4-keV X-ray filaments and jet-like structures possibly caused by Sgr A*. We infer that these complexities in morphology and spectrum of the GC X-ray are due to coupled actions of recent supernova explosions, a super massive black hole and giant molecular clouds.

J1432+158: the most distant giant quasar

We present low-frequency, Giant Metrewave Radio Telescope (GMRT) observations at 333 and 617 MHz of the most distant giant quasar, J1432+158, which is at a redshift of 1.005. The radio source has a total angular extent of 168 arcsec, corresponding to a projected linear size of 1.35 Mpc. This makes it presently the largest single object observed beyond a redshift of 1. The objectives of the GMRT observations were to investigate the possibility of detecting a bridge of emission at low frequencies, which may be suppressed due to inverse-Compton losses against the cosmic microwave background radiation. We detect a jet-like structure connecting the core to the western hotspot, while the eastern hotspot is found to be largely tailless with no significant bridge emission. The estimated lifetime for the radiating electrons in the tail of the western lobe appears smaller than the travel time of the radiating particles from the hotspot, suggesting either in situ acceleration or dissipation of energy by the jet at this location. The pressure of the intergalactic medium at z ∼ 1 estimated from the minimum energy density calculations appears to be marginally lower than the value extrapolated from nearby giant radio galaxies.