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Journal articles on the topic 'Molecular jets'

Author: Grafiati

Published: 4 June 2021

Last updated: 1 February 2022

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1

Smith, Michael D., Roland Völker, Gerhard Suttner, and Harold W. Yorke. "The Class 0 Outflow Hammered Out?" Symposium - International Astronomical Union 182 (1997): 303–12. http://dx.doi.org/10.1017/s0074180900061726.

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Dense molecular jets cutting through dense molecular clouds are simulated here using a ZEUS-type hydrodynamics code extended with molecular physics. H2 ‘hot snapshots’ and CO ‘historical views’ are nicely modelled with overdense uniform jets. Attention is drawn to some remaining hot problems: observed jet knots are bow shaped, bipolar outflows can be highly asymmetric, some proper motions within jets are enigmatically low and H2 excitation can be exceedingly uniform.We present the Hammer Jet, in which the nozzle introduces high velocity variations, as well as a strong ripping and spray action. Prominent jet bow shocks in H2 and CO emission lines are then produced. Wide tubular CO structures with concave bases show up. Proper motions are simulated. The asymmetries are modelled by jet break-out from a molecular core into a diffuse atomic environment.

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2

Hollenbach, David. "The Physics of Molecular Shocks in YSO Outflows." Symposium - International Astronomical Union 182 (1997): 181–98. http://dx.doi.org/10.1017/s0074180900061647.

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Shock waves light up the jets, winds and outflows around YSOs and diagnose the physical conditions and processes resident in these regions. This paper discusses the differences between the jet/wind shock and the ambient shock, between C shocks and J shocks, and between the shocks produced by pure jets and by collimated wide angle winds. Basic shock physics is briefly reviewed, with a special focus on the temperature structure in shocks and the Wardle instability of C shocks. Application is made to the origin of shocked H2 emission and to H2O masers.

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3

Hirano, Naomi, Paul P. T. Ho, Sheng-Yuan Liu, Hsien Shang, Chin-Fei Lee, and Tyler L. Bourke. "EXTREME ACTIVE MOLECULAR JETS IN L1448C." Astrophysical Journal 717, no. 1 (June 7, 2010): 58–73. http://dx.doi.org/10.1088/0004-637x/717/1/58.

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4

Snell, Ronald L. "Structure and kinematics of molecular jets." Canadian Journal of Physics 64, no. 4 (April 1, 1986): 431–33. http://dx.doi.org/10.1139/p86-077.

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Observational studies of the structure and kinematics of the supersonic molecular gas in star-forming regions are reviewed. These studies have suggested that the bulk of the high-velocity gas may be ambient-cloud material swept up by a collimated stellar wind. The actual structures of these outflows, however, are poorly understood. One source that may provide a better understanding of molecular outflows is that in the nearby dark cloud L1551. New observations of this outflow are presented and discussed in context of the models proposed by Snell and Schloerb.

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5

Smith, M. D., and A. Rosen. "Hydrodynamic simulations of rotating molecular jets." Monthly Notices of the Royal Astronomical Society 378, no. 2 (June 21, 2007): 691–700. http://dx.doi.org/10.1111/j.1365-2966.2007.11816.x.

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6

Tabone, B., B. Godard, G. Pineau des Forêts, S. Cabrit, and E. F. van Dishoeck. "Molecule formation in dust-poor irradiated jets." Astronomy & Astrophysics 636 (April 2020): A60. http://dx.doi.org/10.1051/0004-6361/201937383.

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Context. Recent ALMA observations suggest that the highest velocity part of molecular protostellar jets (≳80 km s−1) are launched from the dust-sublimation regions of the accretion disks (≲0.3 au). However, the formation and survival of molecules in inner protostellar disk winds, in the presence of a harsh far-ultraviolet radiation field and the absence of dust, remains unexplored. Aims. We aim to determine if simple molecules, such as H2, CO, SiO, and H2O, can be synthesized and spared in fast and collimated dust-free disk winds or if a fraction of dust is necessary to explain the observed molecular abundances. Methods. This work is based on a recent version of the Paris-Durham shock code designed to model irradiated environments. Fundamental properties of the dust-free chemistry are investigated from single point models. A laminar 1D disk wind model was then built using a parametric flow geometry. This model includes time-dependent chemistry and the attenuation of the radiation field by gas-phase photoprocesses. The influence of the mass-loss rate of the wind and of the fraction of dust on the synthesis of the molecules and on the attenuation of the radiation field is studied in detail. Results. We show that a small fraction of H2 (≤10−2), which primarily formed through the H− route, can efficiently initiate molecule synthesis, such as CO and SiO above TK ~ 800 K. We also propose new gas-phase formation routes of H2 that can operate in strong visible radiation fields, involving CH+ for instance. The attenuation of the radiation field by atomic species (e.g., C, Si, and S) proceeds through continuum self-shielding. This process ensures the efficient formation of CO, OH, SiO, and H2O through neutral–neutral reactions and the survival of these molecules. Class 0 dust-free winds with high mass-loss rates (Ṁw ≥ 2 × 10−6 M⊙ yr−1) are predicted to be rich in molecules if warm (TK ≥ 800 K). Interestingly, we also predict a steep decrease in the SiO-to-CO abundance ratio with the decline of mass-loss rate, from Class 0 to Class I protostars. The molecular content of disk winds is very sensitive to the presence of dust, and a mass-fraction of surviving dust as small as 10−5 significantly increases the H2O and SiO abundances. Conclusions. Chemistry of high velocity jets is a powerful tool to probe their content in dust and uncover their launching point. Models of internal shocks are required to fully exploit the current (sub)millimeter observations and prepare future JWST observations.

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7

Tan, Zhi Kai, Zhen Hua Xie, Hong Jie Wang, Bin Liu, Chun Yi Tong, and Yong Jun Tan. "Jet Stabilities in the Electrospraying of Macro-Molecules Solutions for Controllable Micro-Printing." Advanced Materials Research 900 (February 2014): 531–37. http://dx.doi.org/10.4028/www.scientific.net/amr.900.531.

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Electrospraying (ES) is of great interest in research for its finely controlled delivery of biomaterials. This study investigated mechanisms involved in the electrospraying of biological macro-molecules which may cause spraying instabilities. Hyaluronan (HA) solutions with concentrations ranging from 1 to 5 w/v % (w in g and v in 100 ml) were prepared for spraying trials using nozzles with a size of 30 μm. In electrifying HA solutions with a high molecular weight of 2.1 MDa, controllable jets can be achieved only at the lowest concentration of 1 w/v %. Generally, further use of a sonication method to reduce the molecular size, stable cone jets can be performed relatively easily than using HA solutions of higher concentrations. The improvement of spray stabilities can be attributed to the reduction in viscosity of the solutions after the sonication. Steady micro-sized jets were observed during the ES process and the jet size was found to increase with the increase of both the molecular size and the concentration. Both parameters can be directly ascribed to the rheological property of the solutions. Results show that a suitable viscosity is critically important in stabilizing the electrospray of macro-molecules. A concentration reduction of HA molecules also happens during electrospraying, which indicates that there is a partial reflection of macro-molecules inside the Taylor-cone with the fluid motions during the spraying process. This partial reflection process is affected by molecular sizes, solution concentrations and spraying time.

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8

Eislöffel, Jochen. "Molecular Hydrogen Emission in Embedded Flows." Symposium - International Astronomical Union 182 (1997): 93–102. http://dx.doi.org/10.1017/s007418090006157x.

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This overview of recent observations of molecular hydrogen (H2) in outflows from young stars discusses the morphology, the excitation and the kinematics of the H2 gas in these flows. A comparison between the H2 and CO outflows will lead us to the conclusion that highly-collimated jets may drive the latter. We also discuss the mechanisms which can entrain ambient molecular gas into the jet flow.

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9

Imai, Hiroshi, Tetsuo Sasao, Kumiko Obara, Toshihiro Omodaka, and Philip J. Diamond. "A collimated molecular jet in W 43A traced by water maser emission." Symposium - International Astronomical Union 206 (2002): 80–83. http://dx.doi.org/10.1017/s0074180900222110.

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We present the spatial and velocity distributions of water masers in W 43A. Most of the maser features are spatially and kinematically collimated to a surprising extent. It is very likely that the jet in W 43A is predominantly composed of warm molecules traced by water maser emission. The position angle of the spatial collimation of the maser clusters is slightly different from the directions of both the cluster separation and the proper motions. We propose a model involving a precessing jet to explain the axis offsets. The discovery of a molecular jet with precession in W 43A provides important information on our understanding of the formation of collimated molecular jets and may provide clues on specific stages of stellar evolution.

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10

Mundt, Reinhard. "Jets From Young Stars." International Astronomical Union Colloquium 89 (1986): 6–9. http://dx.doi.org/10.1017/s0252921100085997.

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AbstractRecent optical observations have shown that many young stars are capable of generating highly-collimated bipolar flows. Such flows are evident from narrow emission-line jets extending over 0.01-1 pc and having opening angles of a few degrees. Their measured radial velocities reach values of up to 400 km/s. For most known jets the “driving stars” are T Tauri stars or IR-sources of low to moderate luminosity (1-100 L⊙) . The typical velocities, Mach numbers, particle densities, and mass fluxes of these jets are estimated to be 200-400 km/s, 10-40, 15-150 cm−3, and 10−10−10−7 M⊙/yr, respectively. The estimated mass fluxes and velocities are consistent with our present knowledge of T Tauri star wind properties.The emission-line spectra of the jets are the same as observed in Herbig-Haro (HH) objects. Furthermore, the brightest parts of some jets (hot spots) are known as HH objects, having often been discovered many years before their associated jet. Thus, both phenomena are highly related and in both cases the emission lines are very probably formed in the cooling regions of shock waves with velocities of 50-100 km/s. There are a variety of mechanisms, which can in principal excite internal (oblique) Shockwaves in these jets. Examples of likely excitation mechanisms are fluid dynamical instabilities or pressure gradients in the ambient medium.A model is proposed in which HH objects are representing the locations of the most strongly radiating (internal)shock waves in these jets. For those HH objects being located at the end of the jet the observational data strongly suggest that they are tracing the working surface of the jet. This idea is consistent with the observed proper motions of these HH objects, the typical densities near the edges of their associated molecular clouds, and with the jet parameter given above. For a more detailed discussion of these jets the reader is refered to the review articles listed below.

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11

López-Cámara, D., and A. C. Raga. "Side-entrainment in a jet embedded in a sidewind." Proceedings of the International Astronomical Union 6, S275 (September 2010): 400–401. http://dx.doi.org/10.1017/s1743921310016479.

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AbstractIn this study, we present the results from 3D simulations in which a side-streaming motion pushes the post-bow shock into direct contact with the jet beam. This is a possible mechanism for modeling well collimated molecular jets as an atomic/ionic flow which entrains molecules initially present only in the surrounding environment.

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12

Breidenthal, R. E., V. R. Buonadonna, and M. F. Weisbach. "Molecular mixing via jets in confined volumes." Journal of Fluid Mechanics 219, no. -1 (October 1990): 531. http://dx.doi.org/10.1017/s0022112090003068.

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13

Imai, Hiroshi. "Stellar molecular jets traced by maser emission." Proceedings of the International Astronomical Union 3, S242 (March 2007): 279–86. http://dx.doi.org/10.1017/s1743921307013130.

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AbstractHighly collimated jets found in AGB and post-AGB stars are expected to play an important role for shaping planetary nebulae. Recent VLBI observations of H2o maser sources have revealed that some of the spatio-kinematical structures of H2o maser sources exhibit stellar jets with extremely spatially and kinematically high collimation. Such stellar H2o maser jets, so-called “water fountains”, have been identified in about 10 sources to date. Here we review recent VLBI observations and relevant observational results of the water fountain sources. They have revealed a typical dynamical age and the detailed kinematical structures of the water fountains, the possibility of the existence of “equatorial flows”, and the evolutionary status of the host stars. The location and kinematics of one of the water fountain sources in the Galaxy is also revealed and shown here.

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14

Montero, S. "Molecular description of steady supersonic free jets." Physics of Fluids 29, no. 9 (September 2017): 096101. http://dx.doi.org/10.1063/1.5001250.

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15

Stanke, Thomas. "Observations of molecular jets in Orion A." Astrophysics and Space Science 287, no. 1-4 (2003): 149–60. http://dx.doi.org/10.1023/b:astr.0000006215.36397.fe.

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16

Padman, Rachael, and John S. Richer. "Interactions between molecular outflows and optical jets." Astrophysics and Space Science 216, no. 1-2 (June 1994): 129–34. http://dx.doi.org/10.1007/bf00982480.

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17

Snell, Ronald L. "Bipolar Outflows and Stellar Jets." Symposium - International Astronomical Union 115 (1987): 213–37. http://dx.doi.org/10.1017/s0074180900095607.

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A wealth of data is now available on the energetic mass outflows that are associated with young stellar objects. This phenomenon is thought to occur at a very early stage in the evolution of stars of almost all masses. The discovery of this energetic event was first made through observations of the rapidly expanding molecular gas that surrounds many of these young stellar objects. A review of the physical properties, including the energetics and morphology, of the expanding molecular gas is presented in this paper. In addition, the role these energetic winds play in affecting the dynamics of the parental molecular clouds is also discussed. Finally, the results of detailed studies of the structure and kinematics of the high velocity molecular gas are reviewed and the evidence for existance of wind-swept cavities and molecular shells within the clouds are presented.

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18

Rodríguez, Luis F. "Radio observations of jets from massive young stars." Proceedings of the International Astronomical Union 6, S275 (September 2010): 367–73. http://dx.doi.org/10.1017/s174392131001642x.

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AbstractThe formation of low mass stars takes place with the assistance of an accretion disk that transports gas and dust from the envelope of the system to the star, and a jet that removes angular momentum and allows accretion to proceed. In the radio, these ionized jets can be studied very close to the star via the thermal (free-free) emission they produce and at larger scales by the molecular outflows that result from their interaction with the surrounding medium. Is the same disk-jet process responsible for the formation of massive stars? I will review recent evidence for the presence of collimated jets and accretion disks in association with forming massive stars. The jets in massive protostars have large velocities that could produce a synchrotron component and I discuss the evidence for the presence of this non-thermal process in the jet associated with the HH 80-81 system.

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19

TIAN, FENG-GE, GANG CHEN, and HUI-LING WEI. "THE HARDNESS SPECTRUM OF QUARK- AND GLUON-JETS PRODUCED BY DIFFERENT FLAVOR QUARKS." International Journal of Modern Physics A 23, no. 26 (October 20, 2008): 4337–43. http://dx.doi.org/10.1142/s0217751x08041670.

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The hardness properties of quark- and gluon-jets produced by different flavor quarks are compared in 3-jet events of e+e- collision generated with Monte Carlo Simulation Jetset 7.4 generator at [Formula: see text]. The 3-jet events are obtained using the Durham algorithm and the quark- and gluon-jets are identified by angular-method. The average values of transverse momentum 〈pt〉, multiplicity 〈N〉 and rapidity 〈y〉 versus hardness for quark- and gluon-jets of different flavors are compared. It turns out that the distributions of 〈pt〉, 〈N〉 and 〈y〉 versus hardness of quark-jets are different to their flavors, while those of the gluon-jets are insensitive to the flavors. On the other hand, the 〈pt〉 and 〈N〉 of quark- and gluon-jets are strong positive correlated with hardness, but the 〈y〉 of those are negatively correlated with hardness.

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20

Blome, Hans-Joachim, and Wolfgang Kundt. "Hypersonic jets from young stars in molecular clouds." Symposium - International Astronomical Union 122 (1987): 73–74. http://dx.doi.org/10.1017/s0074180900155974.

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We argue that the narrow jets which are sometimes seen to escape from YSOs into an ambient molecular cloud consist of e±-plasma which can be created in stellar magnetospheric discharges and subsequently centrifugally post-accelerated. This high-pressure pair plasma is squeezed into two jets which ram cocoons into the molecular cloud, observed in the form of molecular lobes (outflows).

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21

Jarvis, Miranda. "Feedback from quasars: The prevalence and impact of radio jets." Proceedings of the International Astronomical Union 15, S356 (October 2019): 253. http://dx.doi.org/10.1017/s1743921320003038.

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AbstractI will present our ongoing multi-wavelength study on the prevalence and impact of radio jets in a sample of z < 0.2 type 2 ‘obscured’ quasars who’s high bolometric luminosities make them ideal local analogues of distant, more common, quasars. Despite being classified as ‘radio quiet’ (log L[1.4GHz] = 23.3 - 24.4 W/Hz), our high spatial resolution (∼0.25”) radio observations (VLA and eMERLIN) reveal jet like structures on 1–25kpc scales in ∼80% of the sample. Our integral field spectroscopy reveals jet-ISM interaction and outflows in all cases. Our work suggests that radio jets are an important feedback mechanism even during a typical ‘quasar’ phase. Using ALMA and APEX we are now investigating the impact of these jets and outflows on the molecular, star forming, gas; looking for signs of depletion and excitation. Preliminary results suggest a depleted molecular gas supply in these sources. I will present all of these results, focused on our pilot study of 10 targets and then introduce our on-going work on an expanded sample of 42 low-redshift quasars. Our latest results come from MUSE/AO and ALMA from which we are carefully characterising the properties of the ionised and molecular outflows at sub-kpc resolution.

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22

Rosen, A., and M. D. Smith. "Simulations of evolving or outbursting molecular protostellar jets." Monthly Notices of the Royal Astronomical Society 343, no. 1 (July 21, 2003): 181–91. http://dx.doi.org/10.1046/j.1365-8711.2003.06654.x.

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23

Oomens, Jos, and Jörg Reuss. "Tricky IR Monomer Spectroscopy in Planar Molecular Jets." Israel Journal of Chemistry 37, no. 4 (1997): 367–78. http://dx.doi.org/10.1002/ijch.199700042.

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24

Burshtein, A. I. "Nearly collisionless sub-Doppler spectroscopy of molecular jets." Physical Review A 56, no. 5 (November 1, 1997): 3543–52. http://dx.doi.org/10.1103/physreva.56.3543.

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25

Shang, Hsien. "Jets and molecular outflows from Herbig-Haro objects." Astrophysics and Space Science 311, no. 1-3 (August 9, 2007): 25–34. http://dx.doi.org/10.1007/s10509-007-9587-4.

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26

Saltó, Oriol. "+ Jets and + Heavy Flavor Jets at the Tevatron." Nuclear Physics B - Proceedings Supplements 186 (January 2009): 15–18. http://dx.doi.org/10.1016/j.nuclphysbps.2008.12.003.

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27

Kavak, Ü., Á. Sánchez-Monge, A. López-Sepulcre, R. Cesaroni, F. F. S. van der Tak, L. Moscadelli, M. T. Beltrán, and P. Schilke. "Search for radio jets from massive young stellar objects." Astronomy & Astrophysics 645 (December 24, 2020): A29. http://dx.doi.org/10.1051/0004-6361/202037652.

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Context. Recent theoretical and observational studies debate the similarities of the formation process of high- (>8 M⊙) and low-mass stars. The formation of low-mass stars is directly associated with the presence of disks and jets. Theoretical models predict that stars with masses up to 140 M⊙ can be formed through disk-mediated accretion in disk-jet systems. According to this scenario, radio jets are expected to be common in high-mass star-forming regions. Aims. We aim to increase the number of known radio jets in high-mass star-forming regions by searching for radio-jet candidates at radio continuum wavelengths. Methods. We used the Karl G. Jansky Very Large Array (VLA) to observe 18 high-mass star-forming regions in the C band (6 cm, ≈1′′.0 resolution) and K band (1.3 cm, ≈0′′.3 resolution). We searched for radio-jet candidates by studying the association of radio continuum sources with shock activity signs (e.g., molecular outflows, extended green objects, and maser emission). Our VLA observations also targeted the 22 GHz H2O and 6.7 GHz CH3OH maser lines. Results. We have identified 146 radio continuum sources, 40 of which are located within the field of view of both images (C and K band maps). We derived the spectral index, which is consistent with thermal emission (between − 0.1 and + 2.0) for 73% of these sources. Based on the association with shock-activity signs, we identified 28 radio-jet candidates. Out of these, we identified 7 as the most probable radio jets. The radio luminosity of the radio-jet candidates is correlated with the bolometric luminosity and the outflow momentum rate. About 7–36% of the radio-jet candidates are associated with nonthermal emission. The radio-jet candidates associated with 6.7 GHz CH3OH maser emission are preferentially thermal winds and jets, while a considerable fraction of radio-jet candidates associated with H2O masers show nonthermal emission that is likely due to strong shocks. Conclusions. About 60% of the radio continuum sources detected within the field of view of our VLA images are potential radio jets. The remaining sources could be compact H II regions in their early stages of development, or radio jets for which we currently lack further evidence of shock activity. Our sample of 18 regions is divided into 8 less evolved infrared-dark regions and 10 more evolved infrared-bright regions. We found that ≈71% of the identified radio-jet candidates are located in the more evolved regions. Similarly, 25% of the less evolved regions harbor one of the most probable radio jets, while up to 50% of the more evolved regions contain one of these radio-jet candidates. This suggests that the detection of radio jets in high-mass star-forming regions is more likely in slightly more evolved regions.

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28

Emonts, Bjorn. "Jet-CO alignments in the environments high-z radio galaxies." Proceedings of the International Astronomical Union 11, S321 (March 2016): 348–50. http://dx.doi.org/10.1017/s1743921316011613.

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AbstractIn the outskirts of massive high-redshift radio galaxies, powerful radio-jets often interact with ambient warm Lyα-emitting gas. We present the discovery of luminous reservoirs of cold molecular gas in these environments, based on CO(1-0) observations with the Australia Telescope Compact Array. The CO-emission is aligned with the radio jets, and found tens of kpc outside the host galaxy. These molecular gas reservoirs have CO luminosities in the range of those found in submm-galaxies (L'CO ~ 4-9 × 1010 K km/s pc2), but they lack any near-infrared counterpart in deep Spitzer imaging. These results suggest that jet-triggered feedback takes place in the circum-galactic environment of high-z radio galaxies. We prefer the interpretation that the CO-emitting gas is formed when the propagating jets enrich, shock and cool pre-existing dusty halo gas. We further argue that sensitive low-surface-brightness CO observations, using radio interferometers in very compact array-configurations, are essential to study the role of the cold molecular medium in the outskirts of massive high-z galaxies.

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29

Tsinganos, K., A. Ferrari, and R. Rosner. "Quasi-Two-Dimensional Cosmic Jets." Symposium - International Astronomical Union 107 (1985): 497–501. http://dx.doi.org/10.1017/s0074180900076014.

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One of the major discoveries in solar physics over the past decade has been the association of coronal holes with high-speed solar wind streams (Zirker 1977 and references therein). On the other hand, advances in X-ray and radio instrumentation (e.g., Einstein, VLA, VLBI, etc.) in the past few years have allowed detailed observations of collimated outflows from rather more distant objects, such as young stars and active galaxies (Beer 1981, Lada 1982, Ferrari and Pacholczyk 1983 and references therein). The remarkable structural similarities between jets of magnetized gas from our Sun, other active stars, and active galactic nuclei suggest that these phenomena may be manifestations of similar hydrodynamic processes operating on both small and large scales. In this article, we shall use the experience gained by studying the nearest known astrophysical jet - high-speed solar wind streams - to address some of the problems of astrophysical jet acceleration and collimation associated with objects as diverse as SS 433, star-forming molecular clouds and, in particular, jets associated with galaxies and quasars.

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Zovaro, Henry R. M., Nicole P. H. Nesvadba, Robert Sharp, Geoffrey V. Bicknell, Brent Groves, Dipanjan Mukherjee, and Alexander Y. Wagner. "Searching for signs of jet-driven negative feedback in the nearby radio galaxy UGC 05771." Monthly Notices of the Royal Astronomical Society 489, no. 4 (September 5, 2019): 4944–61. http://dx.doi.org/10.1093/mnras/stz2459.

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ABSTRACT Hydrodynamical simulations predict that the jets of young radio sources can inhibit star formation in their host galaxies by injecting heat and turbulence into the interstellar medium (ISM). To investigate jet–ISM interactions in a galaxy with a young radio source, we have carried out a multiwavelength study of the z = 0.025 Compact Steep Spectrum radio source hosted by the early-type galaxy UGC 05771. Using Keck/OSIRIS observations, we detected H2 1–0 S(1) and [Fe ii] emission at radii of 100s of parsecs, which traces shocked molecular and ionized gas being accelerated outwards by the jets to low velocities, creating a ‘stalling wind’. At kpc radii, we detected shocked ionized gas using observations from the CALIFA survey, covering an area much larger than the pc-scale radio source. We found that existing interferometric radio observations fail to recover a large fraction of the source’s total flux, indicating the likely existence of jet plasma on kpc scales, which is consistent with the extent of shocked gas in the host galaxy. To investigate the star formation efficiency in UGC 05771, we obtained IRAM CO observations to analyse the molecular gas properties. We found that UGC 05771 sits below the Kennicutt–Schmidt relation, although we were unable to definitively conclude if direct interactions from the jets are inhibiting star formation. This result shows that jets may be important in regulating star formation in the host galaxies of compact radio sources.

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31

Königl, Arieh. "Stellar and galactic jets: theoretical issues." Canadian Journal of Physics 64, no. 4 (April 1, 1986): 362–68. http://dx.doi.org/10.1139/p86-063.

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Theoretical issues pertaining to the modelling of jets in young stellar objects and in active galactic nuclei are reviewed. The strong morphological similarities between these two types of sources are emphasized, and observational constraints on the basic physical mechanisms that may be responsible for the jet phenomenon are outlined. Particular attention is given to the "momentum-discharge problem" in molecular-cloud outflows and to its possible resolution in terms of a centrifugally driven magnetohydrodynamic wind from an accretion disk. In addition, various propagation effects are discussed, and the relevance to stellar jets of the de Laval collimation mechanism and of the accelerated-clump model for emission knots is assessed. The review concludes with a brief list of potentially useful observational tests.

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32

Morganti, Raffaella. "Radio jets: Properties, life and impact." Proceedings of the International Astronomical Union 15, S356 (October 2019): 229–42. http://dx.doi.org/10.1017/s1743921320002999.

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AbstractOur view of the properties of extragalactic radio jets and the impact they have on the host galaxy has expanded in the recent years. This has been possible thanks to the data from new or upgraded radio telescopes. This review briefly summarises the current status of the field and describes some of the exciting recent results and the surprises they have brought. In particular, the physical properties of radio jets as function of their radio power will be discussed together with the advance made in understanding the life-cycle of radio sources. The evolutionary stage (e.g. newly born, dying, restarted) of the radio AGN can be derived from their morphology and properties of the radio spectra. The possibilities offered by the new generation of low-frequency radio telescopes make it possible to derive (at least to first order) the time-scale spent in each phase. The presence of a cycle of activity ensures a recurrent impact of the radio jets on their surrounding inter-stellar and inter-galactic medium and, therefore, their relevance for AGN feedback. The last part is dedicated to the recent results showing the effect of jets on the surrounding galactic medium. The predictions made by numerical simulations on the impact of a radio jet (and in particular a newly born jet) on a clumpy medium describe well what is seen by the observations. The high resolution studies of jet-driven outflows of cold gas (and molecular) has provided new important addition both in term of quantifying the impact of the outflows and their relevance for feedback as well as for providing an unexpected view of the physical conditions of the gas under these extreme conditions.

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33

Raga, A. C., D. López-Cámara, J. Cantó, A. Esquivel, A. Rodríguez-González, and P. F. Velázquez. "Development of jets, outflows and HH objects." Proceedings of the International Astronomical Union 5, H15 (November 2009): 515–16. http://dx.doi.org/10.1017/s1743921310010458.

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The entrainment of molecular material through a mixing layer along the walls of a HH jet beam has been modeled analytically (Cantó & Raga 1991; Stahler 1994) and numerically (Taylor & Raga 1995; Lim et al. 1999). However, when full radiative jet simulations are carried out, the molecular, environmental material remains within a dense shell which follows the shape of the leading bow shock. Because of this, no molecular material reaches the outer boundary of the jet beam, and therefore no “side-entrainment” of molecular gas into the fast jet beam takes place.

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34

Qiu, Jing, Baifei Shen, Lingang Zhang, Xiaomei Zhang, Shan Huang, Lihua Cao, and Wei Yu. "Generation of collimated electron jets from plasma under applied electromagnetostatic field." Laser and Particle Beams 36, no. 3 (September 2018): 384–90. http://dx.doi.org/10.1017/s0263034618000381.

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AbstractThe collimated electron jets ejected from cylindrical plasma are produced in particle-in-cell simulation under the applied longitudinal magnetostatic field and radial electrostatic field, which is a process that can be conveniently performed in a laboratory. We find that the applied magnetostatic field contributes significantly to the jet collimation, whereas the applied electrostatic field plays a vital role in the jet formation. The generation mechanism of collimated jets can be well understood through energy gain of the tagged electrons, and we conclude that the longitudinal momentum of the electrons is converted from the transverse momentum via the transverse-induced magnetic field. It has been found that the ejecting velocity of the jets is close to the speed of light when the applied electrostatic field reaches 3 × 1010 V/m. The present scheme may also give us an insight into the formation of astrophysical jets in celestial bodies.

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Li, Qiang, Chunlan Jiang, and Ye Du. "Molecular-Dynamics Study on the Impact Energy Release Characteristics of Fe–Al Energetic Jets." Materials 14, no. 18 (September 13, 2021): 5249. http://dx.doi.org/10.3390/ma14185249.

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Fe–Al energetic material releases a large amount of energy under impact loading; therefore, it can replace traditional materials and be used in new weapons. This paper introduces the macroscopic experiment and microscopic molecular-dynamics simulation research on the energy release characteristics of Fe–Al energetic jets under impact loading. A macroscopic dynamic energy acquisition test system was established to quantitatively obtain the composition of Fe–Al energetic jet reaction products. A momentum mirror impacting the Fe–Al particle molecular model was established and the microstructure evolution and impact thermodynamic response of Fe–Al particles under impact loading were analyzed. The mechanism of multi-scale shock-induced chemical reaction of Fe–Al energetic jets is discussed. The results show that the difference in velocity between Fe and Al atoms at the shock wave fronts is the cause of the shock-induced reaction; when the impact strength is low, the Al particles are disordered and amorphous, while the Fe particles remain in their original state and only the oxidation reaction of Al and a small amount intermetallic compound reaction occur. With the increase of impact strength, Al particles and Fe particles are completely disordered and amorphized in a high-temperature and high-pressure environment, fully mixed and penetrated. The temperature of the system rises rapidly, due to a violent thermite reaction, and the energy released by the jet shows an increasing trend; there is an impact intensity threshold, so that the jet release energy reaches the upper limit.

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36

Cernicharo, J., R. Neri, and Bo Reipurth. "The Molecular Outflow and CO Bullets in HH111." Symposium - International Astronomical Union 182 (1997): 141–52. http://dx.doi.org/10.1017/s0074180900061611.

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We present high angular resolution observations of the molecular outflow associated with the optical jet and HH objects of the HH111 system. Interferometric observations in the CO J =2–1 and J =1–0 lines of the high velocity bullets associated with HH111 are presented for the first time. The molecular gas in these high velocity clumps has a moderate kinetic temperature and a mass of a few 10–4 M⊙ per bullet. We favor the view that HH jets and CO bullets, which represent different manifestations of the same physical phenomena, are driving the low-velocity molecular outflow.

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37

Xie, C., S. Y. Haffert, J. de Boer, M. A. Kenworthy, J. Brinchmann, J. Girard, I. A. G. Snellen, and C. U. Keller. "A MUSE view of the asymmetric jet from HD 163296." Astronomy & Astrophysics 650 (June 2021): L6. http://dx.doi.org/10.1051/0004-6361/202140602.

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Context. Jets and outflows are thought to play important roles in regulating star formation and disk evolution. An important question is how the jets are launched. HD 163296 is a well-studied Herbig Ae star that hosts proto-planet candidates, a protoplanetary disk, a protostellar jet, and a molecular outflow, which makes it an excellent laboratory for studying jets. Aims. We aim to characterize the jet at the inner regions and check if there are large differences with the features at large separations. A secondary objective is to demonstrate the performance of Multi Unit Spectroscopic Explorer (MUSE) in high-contrast imaging of extended line emission. Methods. MUSE in the narrow field mode (NFM) can provide observations at optical wavelengths with high spatial (∼75 mas) and medium spectral (R ∼ 2500) resolution. With the high-resolution spectral differential imaging technique, we can characterize the kinematic structures and physical conditions of jets down to 100 mas. Results. We detect multiple atomic lines in two new knots, B3 and A4, at distances of < 4″ from the host star with MUSE. The derived Ṁjet/Ṁacc is about 0.08 and 0.06 for knots B3 and A4, respectively. The observed [Ca II]/[S II] ratios indicate that there is no sign of dust grains at distances of < 4″. Assuming the A4 knot traced the streamline, we can estimate a jet radius at the origin by fitting the half width half maximum of the jet, which sets an upper limit of 2.2 au on the size of the launching region. Although MUSE has the ability to detect the velocity shifts caused by high- and low-velocity components, we found no significant evidence of velocity decrease transverse to the jet direction in our 500 s MUSE observation. Conclusions. Our work demonstrates the capability of using MUSE NFM observations for the detailed study of stellar jets in the optical down to 100 mas. The derived Ṁjet/Ṁacc, no dust grain, and jet radius at the star support the magneto-centrifugal models as a launching mechanism for the jet.

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Smith, M. D., and P. W. J. L. Brand. "Jet Interactions with Molecular Clouds: C–Shock Models." Symposium - International Astronomical Union 140 (1990): 332. http://dx.doi.org/10.1017/s0074180900190412.

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Molecular hydrogen emission lines are associated with collimated outflows from young stellar objects. They have been measured near Herbig–Haro objects within jets as well as at the jet termination. Similarly to HH objects, the lines are produced from radiative shocks which may be in the form of oblique internal jet shocks or bow shocks. A J-shock can only be invoked in a dynamical model context since the H2 lines are often wide (> 30 km s−1). The alternative is the MHD C–shock in which the ionisation level is sufficiently low so that the magnetic field and ions interact weakly with the neutrals. We have investigated C-shock flows by employing approximate forms for the ion-neutral drag, cooling and other processes with the following results.

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Wang, Mei-Yan, C. Muthumariappan, and Sun Kwok. "Molecular Hydrogen Jets, Filaments, and Haloes in Planetary Nebulae." Proceedings of the International Astronomical Union 2, S234 (April 2006): 537. http://dx.doi.org/10.1017/s1743921306004121.

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40

Lietz, Amanda M., and Mark J. Kushner. "Molecular admixtures and impurities in atmospheric pressure plasma jets." Journal of Applied Physics 124, no. 15 (October 21, 2018): 153303. http://dx.doi.org/10.1063/1.5049430.

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41

Cliffe, J. A., Adam Frank, and T. W. Jones. "Precessing jets and molecular outflows: a 3D numerical study." Monthly Notices of the Royal Astronomical Society 282, no. 4 (October 1996): 1114–28. http://dx.doi.org/10.1093/mnras/282.4.1114.

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42

Banerjee, Robi, Ralf S. Klessen, and Christian Fendt. "Can Protostellar Jets Drive Supersonic Turbulence in Molecular Clouds?" Astrophysical Journal 668, no. 2 (October 20, 2007): 1028–41. http://dx.doi.org/10.1086/521097.

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43

Giannini, T., D. Lorenzetti, M. De Luca, F. Strafella, D. Elia, B. Maiolo, M. Marengo, et al. "SPITZER-IRAC SURVEY OF MOLECULAR JETS IN VELA-D." Astrophysical Journal 767, no. 2 (April 5, 2013): 147. http://dx.doi.org/10.1088/0004-637x/767/2/147.

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44

Bally, John, David Devine, Robert A. Fesen, and Adair P. Lane. "Twin Herbig-Haro Jets and Molecular Outflows in L1228." Astrophysical Journal 454 (November 1995): 345. http://dx.doi.org/10.1086/176486.

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45

Moraghan, Anthony, Michael D. Smith, and Alexander Rosen. "Velocity study of axisymmetric protostellar jets with molecular cooling." Monthly Notices of the Royal Astronomical Society 371, no. 3 (September 21, 2006): 1448–58. http://dx.doi.org/10.1111/j.1365-2966.2006.10791.x.

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46

CIARDI, A., S. V. LEBEDEV, J. P. CHITTENDEN, and S. N. BLAND. "Modeling of supersonic jet formation in conical wire array Z-pinches." Laser and Particle Beams 20, no. 2 (April 2002): 255–61. http://dx.doi.org/10.1017/s0263034602202153.

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Supersonic jet production in conical wire array Z-pinches is modeled using a two-dimensional (2D) resistive magneto-hydrodynamic (MHD) code. In conical wire arrays, the converging plasma ablated from the wires stagnates on axis, forming a standing conical shock which redirects and collimates the flow into a jet. As the jet exits the collimator shock, it is radiatively cooled and accelerated by the steep thermal gradients present. Purely hydrodynamic simulations using conditions relevant to the MAGPIE facility show good agreement with the experiments (Lebedev et al., 2002), indicating that narrow, high Mach number (M ∼ 20), radiatively cooled tungsten jets of astrophysical relevance can be obtained. To investigate the effects of lower radiative cooling on jet collimation, we modeled an aluminum conical wire array. When radiative losses are less significant, lower Mach number (M ∼ 10), less collimated jets are obtained. MHD simulations relevant to the “Z” facility were carried out to investigate the scaling of jet parameters. The resulting hypersonic (M ∼ 40), high density jets should allow the investigation of a wider range of astrophysical jet conditions.

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47

Carnovale, Frank, J. Barrie Peel, and Richard G Rothwell. "Photoelectron Spectroscopy using Pulsed Free Jets." Australian Journal of Physics 39, no. 5 (1986): 789. http://dx.doi.org/10.1071/ph860789.

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The use of pulsed gaseous free jets in the study of atomic and molecular species by ultraviolet photoelectron spectroscopy (UPS) offers a number of advantages over the usual continuous flow room temperature technique. Pulsed free jet expansions provide, on the one hand, 'cold' molecules for which spectroscopy is simplified through the absence of hot band structure and, on the other hand, cluster species including dimers, trimers and higher clusters, as well as intermolecular species, all generally of low intermolecular binding energies. Furthermore a high pressure gas pulse is a suitable medium for the preparation, relaxation and transport of reactive species formed in processes such as pyrolysis, photodissociation or electrical discharge. This paper describes the modifications made to an ultraviolet photoelectron spectrometer to allow measurements on pulsed free jet expansions. The important features of the modified instrument concern the control of the gas beam and the timing electronics for photoelectron detection. Examples of He I photoelectron spectra presented include (a) the demonstration of hot band structure in the room temperature UPS of ammonia, (b) the preparation of the dimer (NOh and higher clusters (NO) n of nitric oxide, (c) the UPS of sulfur dioxide clusters (S02) n' and (d) the UPS of ammonia clusters (NH 3) n'

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48

Plante, R. L., T. Handa, and K. Y. Lo. "Jet-Cloud Interactions in NGC 4258: CO Observations Using the Nobeyama Millimeter Array." International Astronomical Union Colloquium 140 (1994): 359–60. http://dx.doi.org/10.1017/s0252921100019990.

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Recent CO studies of spiral galaxy NGC 4258 have revealed a close relationship between the molecular gas and the anomalous arms, recently interpreted as jets (Cecil et al. 1992, Martin et al. 1990). An IRAM single dish study by Krause et al. (1991) showed the CO to be concentrated around the Hα arms. Interferometrie imaging of the inner 1’ by Martin et al. (1990) showed the molecular gas confining the arms; they suggested that the jet had initially plowed a tunnel through the disk gas, producing a free path for subsequent ejections. This data also shows strong evidence for a jet-cloud collision along the N W arm (Piante et al. 1991).To learn more about the jets, we are motivated to exploit the jet-gas relationship with multi-field imaging of the CO along the anomalous arms using the Nobeyama Millimeter Array. We present preliminary results from our first 60” field, centered on the SE Hα arm, 43.5” from the nucleus. Observations in the two most compact configurations (C and D) produced a 4” x 6” beam.

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Ruffa, Ilaria, Robert A. Laing, Isabella Prandoni, Rosita Paladino, Paola Parma, Timothy A. Davis, and Martin Bureau. "The AGN fuelling/feedback cycle in nearby radio galaxies – III. 3D relative orientations of radio jets and CO discs and their interaction." Monthly Notices of the Royal Astronomical Society 499, no. 4 (October 14, 2020): 5719–31. http://dx.doi.org/10.1093/mnras/staa3166.

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ABSTRACT This is the third paper of a series exploring the multifrequency properties of a sample of eleven nearby low-excitation radio galaxies (LERGs) in the southern sky. We are conducting an extensive study of different galaxy components (stars, dust, warm and cold gas, radio jets) with the aim of better understanding the AGN fuelling/feedback cycle in LERGs. Here, we present new, deep, sub-kpc resolution Karl G. Jansky Very Large Array (JVLA) data for five sample sources at 10 GHz. Coupling these data with previously acquired Atacama Large Millimetre/submillimetre Array (ALMA) CO(2–1) observations and measurements of comparable quality from the literature, we carry out for the first time a full 3D analysis of the relative orientations of jet and disc rotation axes in six FR I LERGs. This analysis shows (albeit with significant uncertainties) that the relative orientation angles span a wide range (≈30○–60○). There is no case where both axes are accurately aligned and there is a marginally significant tendency for jets to avoid the disc plane. Our study also provides further evidence for the presence of a jet-CO disc interaction (already inferred from other observational indicators) in at least one source, NGC 3100. In this case, the limited extent of the radio jets, along with distortions in both the molecular gas and the jet components, suggest that the jets are young, interacting with the surrounding matter and rapidly decelerating.

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Padman, Rachael, Stephen Bence, and John Richer. "Observational Properties of Molecular Outflows." Symposium - International Astronomical Union 182 (1997): 123–40. http://dx.doi.org/10.1017/s007418090006160x.

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Molecular outflows are intimately related to the highly collimated Herbig–Haro jets emanating from young stars. In consequence, the usual dynamical timescale significantly underestimates the true age of an outflow. If we correct for this factor, and assume an intrinsic outflow speed similar to that of the underlying jet, we predict that molecular outflows should have an overall extent of several parsecs, in accordance with recent results. It seems likely therefore that outflows are a major source of interstellar turbulence, and have a profound impact on the process of star formation.Whilst interpretation of jet-like outflows is relatively straightforward, the origins of shell-like outflows, such as that from L 1551–IRS5, are less obvious. We discuss the current observational status of both types of flow, and hypothesize an evolutionary connection between them. A large and well-defined outflow sample is urgently required, to permit the establishment of an age-sequence; such a sample would also provide the basis for a proper investigation of outflow energetics and interaction with the ISM.

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