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Tracing the Bipolar Outflow from Orion Source I  [PDF]
R. L. Plambeck,M. C. H. Wright,D. N. Friedel,S. L. Widicus Weaver,A. D. Bolatto,M. W. Pound,D. P. Woody,J. W. Lamb,S. L. Scott
Physics , 2009, DOI: 10.1088/0004-637X/704/1/L25
Abstract: Using CARMA, we imaged the 87 GHz SiO v=0 J=2-1 line toward Orion-KL with 0.45 arcsec angular resolution. The maps indicate that radio source I drives a bipolar outflow into the surrounding molecular cloud along a NE--SW axis, in agreement with the model of Greenhill et al. (2004). The extended high velocity outflow from Orion-KL appears to be a continuation of this compact outflow. High velocity gas extends farthest along a NW--SE axis, suggesting that the outflow direction changes on time scales of a few hundred years.
The discovery based on GLIMPSE data of a protostar driving a bipolar outflow  [PDF]
J. H. Yuan,J. Z. Li,Y. F. Huang,C. H. Hsia,J. Miao
Physics , 2012, DOI: 10.1051/0004-6361/201117858
Abstract: We report the discovery based on GLIMPSE data of a proto-stellar system driving a bipolar outflow . The bipolar outflow closely resembles the shape of an hourglass in the infrared. The total luminosity of L_total=5507 L_sun, derived from IRAS fluxes, indicates the ongoing formation of a massive star in this region. The spectral energy distribution (SED) of the driving source is fitted with an online SED fitting tool, which results in a spectral index of about 1.2. This, along with the presence of a bipolar outflow, suggests the detection of a Class I protostar. The driving source indicates prominent infrared excesses in color-color diagrams based on archived 2MASS and GLIMPSE data, which is in line with an early evolutionary stage of the system.
SMA Submillimeter Observations of HL Tau: Revealing a compact molecular outflow  [PDF]
Alba M. Lumbreras,Luis A. Zapata
Physics , 2014, DOI: 10.1088/0004-6256/147/4/72
Abstract: We present archival high angular resolution ($\sim$ 2$''$) $^{12}$CO(3-2) line and continuum submillimeter observations of the young stellar object HL Tau made with the Submillimeter Array (SMA). The $^{12}$CO(3-2) line observations reveal the presence of a compact and wide opening angle bipolar outflow with a northeast and southwest orientation (P.A. = 50$^\circ$), and that is associated with the optical and infrared jet emanating from HL Tau with a similar orientation. On the other hand, the 850 $\mu$m continuum emission observations exhibit a strong and compact source in the position of HL Tau that has a spatial size of $\sim$ 200 $\times$ 70 AU with a P.A. $=$ 145$^\circ$, and a dust mass of around 0.1 M$_\odot$. These physical parameters are in agreement with values obtained recently from millimeter observations. This submillimeter source is therefore related with the disk surrounding HL Tau.
A Fast bipolar H2 outflow from IRAS 16342-3814: an old star reliving its youth  [PDF]
T. M. Gledhill,K. P. Forde
Physics , 2011, DOI: 10.1111/j.1365-2966.2011.20309.x
Abstract: Some evolved stars in the pre-planetary nebula phase produce highly-collimated molecular outflows that resemble the accretion-driven jets and outflows from pre-main sequence stars. We show that IRAS 16342-3814 (the Water Fountain Nebula) is such an object and present K-band integral field spectroscopy revealing a fast (> 150 km/s) bipolar H2 outflow. The H2 emission is shock excited and may arise in fast-moving clumps, accelerated by the previously observed precessing jet. The total luminosity in H2 is 0.37 L$_{\odot}$ which is comparable with that of accretion-powered outflows from Class 0 protostars. We also detect CO overtone bandhead emission in the scattered continuum, indicating hot molecular gas close to the centre, a feature also observed in a number of protostars with active jets. It seems likely that the jet and outflow in IRAS 16342-3814 are powered by accretion onto a binary companion.
The bipolar outflow and disk of the brown dwarf ISO217  [PDF]
V. Joergens,A. Pohl,A. Sicilia-Aguilar,Th. Henning
Physics , 2012, DOI: 10.1051/0004-6361/201219206
Abstract: We show that the very young brown dwarf candidate ISO217 (M6.25) is driving an intrinsically asymmetric bipolar outflow with a stronger and slightly faster red-shifted component based on spectro-astrometry of forbidden [SII] emission lines observed in UVES/VLT spectra taken in 2009. ISO217 is only one of a handful of brown dwarfs and VLMS (M5-M8) for which an outflow has been detected and that show that the T Tauri phase continues at the substellar limit. We measure a spatial extension of the outflow of +/-190mas (+/-30AU) and velocities of +/-40-50kms/s. We show that the velocity asymmetry between both lobes is variable on timescales of a few years and that the strong asymmetry of a factor of 2 found in 2007 might be smaller than originally anticipated when using a more realistic stellar rest-velocity. We also detect forbidden [FeII]7155 emission, for which we propose as potential origin the hot inner regions of the outflow. To understand the ISO217 system, we determine the disk properties based on radiative transfer modeling of the SED. This disk model agrees very well with Herschel/PACS data at 70mu. We find that the disk is flared and intermediately inclined (~45deg). The total disk mass (4e-6 Msun) is small compared to the accretion and outflow rate of ISO217 (~1e-10 Msun/yr). We propose that this discrepancy can be explained by either a higher disk mass than inferred from the model (strong undetected grain growth) and/or by an on average lower accretion and outflow rate than the determined values. We show that a disk inclination significantly exceeding 45deg, as suggested from Halpha modeling and from both lobes of the outflow being visible, is inconsistent with the SED data. Thus, despite its intermediate inclination angle, the disk of this brown dwarf does not appear to obscure the red outflow component, which is very rarely seen for T Tauri objects (only one other case).
Impacts of pure shocks in the BHR71 bipolar outflow  [PDF]
Antoine Gusdorf,Denise Riquelme,Sibylle Anderl,Jochen Eisloeffel,Claudio Codella,Arturo Gomez-Ruiz,Urs Graf,Lars Kristensen,Silvia Leurini,Berengere Parise,Migel Requena-Torres,Oliver Ricken,Rolf Guesten
Physics , 2015, DOI: 10.1051/0004-6361/201425142
Abstract: During the formation of a star, material is ejected along powerful jets that impact the ambient material. This outflow regulates star formation by e.g. inducing turbulence and heating the surrounding gas. Understanding the associated shocks is therefore essential to the study of star formation. We present comparisons of shock models with CO, H2, and SiO observations in a 'pure' shock position in the BHR71 bipolar outflow. These comparisons provide an insight into the shock and pre-shock characteristics, and allow us to understand the energetic and chemical feedback of star formation on Galactic scales. New CO (Jup = 16, 11, 7, 6, 4, 3) observations from the shocked regions with the SOFIA and APEX telescopes are presented and combined with earlier H2 and SiO data (from the Spitzer and APEX telescopes). The integrated intensities are compared to a grid of models that were obtained from a magneto-hydrodynamical shock code which calculates the dynamical and chemical structure of these regions combined with a radiative transfer module based on the 'large velocity gradient' approximation. The CO emission leads us to update the conclusions of our previous shock analysis: pre-shock densities of 1e4 cm-3 and shock velocities around 20-25 km s-1 are still constrained, but older ages are inferred ( 4000 years). We evaluate the contribution of shocks to the excitation of CO around forming stars. The SiO observations are compatible with a scenario where less than 4% of the pre-shock SiO belongs to the grain mantles. We infer outflow parameters: a mass of 1.8x1e-2 Msun was measured in our beam, in which a momentum of 0.4 Msun km s-1 is dissipated, for an energy of 4.2x1e43erg. We analyse the energetics of the outflow species by species. Comparing our results with previous studies highlights their dependence on the method: H2 observations only are not sufficient to evaluate the mass of outflows.
HST/STIS Observations of the Bipolar Jet from RW Aurigae: Tracing Outflow Asymmetries Close to the Source  [PDF]
Jens Woitas,Thomas P. Ray,Francesca Bacciotti,Christopher J. Davis,Jochen Eisl"offel
Physics , 2002, DOI: 10.1086/343124
Abstract: We have observed the bipolar jet from RW Aur A with STIS on board the HST. After continuum subtraction, morphological and kinematic properties of this outflow can be traced to within 0."1 from the source in forbidden emission lines. The jet appears well collimated, with typical FWHMs of 20 to 30 AU in the first 2" and surprisingly does not show a separate low-velocity component in contrast to earlier observations. The systemic radial outflow velocity of the blueshifted lobe is typically 50% larger than that of the redshifted one with a velocity difference of about 65 km/s. Although such asymmetries have been seen before on larger scales, our high spatial resolution observations suggest that they are intrinsic to the "central engine" rather than effects of the star's immediate environment. Temporal variations of the bipolar jet's outflow velocities appear to occur on timescales of a few years. They have combined to produce a 55% increase in the velocity asymmetry between the two lobes over the past decade. In the red lobe estimated mass flux and momentum flux values are around one half and one third of those for the blue lobe, respectively. The mass outflow to mass accretion rate is 0.05, the former being measured at a distance of 0."35 from the source.
SOFIA observations of CO(12-11) emission along the L1157 bipolar outflow  [PDF]
Jochen Eisl?ffel,Brunella Nisini,Rolf Güsten,Helmut Wiesemeyer,Antoine Gusdorf
Physics , 2012, DOI: 10.1051/0004-6361/201218901
Abstract: Carbon monoxide is an excellent tracer of the physical conditions of gas in molecular outflows from young stars. To understand the outflow mechanism we need to investigate the origin of the molecular emission and the structure and interaction of the outflowing molecular gas. Deriving the physical parameters of the gas will help us to trace and understand the various gas components in the flow. We observed CO(12-11) line emission at various positions along the L1157 bipolar outflow with GREAT aboard SOFIA. Comparing these new data with CO(2-1), we find basically constant line ratios along the outflow and even at the position of the source. These line ratios lead us to estimates of 10^5 to 10^6 cm^-3 for the gas density and 60 to 100 K for the gas temperature of the outflowing gas. The constrained density and temperature values indicate that we are mostly tracing a low-velocity gas component everywhere along the outflow, which is intermediate between the already known cold gas component, which gets entrained into the flow, and the hot gas, which gets shocked in the outflow.
Multi-wavelength spectroscopy of the bipolar outflow from Cepheus E  [PDF]
M. D. Smith,D. Froebrich,J. Eisl?ffel
Physics , 2003, DOI: 10.1086/375687
Abstract: Cepheus E is the site of an exceptional example of a protostellar outflow with a very young dynamical age and extremely high near infrared luminosity. We combine molecular spectroscopic data from the submillimeter to the near infrared in order to interpret the rotational excitation of CO and the ro-vibrational excitation of H2. We conclude that C-type shocks with a paraboloidal bow shock geometry can simultaneously explain all the molecular excitations. Extinction accounts for the deviation of the column densities from local thermodynamic equilibrium. A difference in the extinction between the red and blue-shifted outflow lobes may account for the measured flux difference. The outflow is deeply embedded in a clump of density 10^5cm^-3, yet a good fraction of atomic hydrogen, about 40%, is required to explain the excitation and statistical equilibrium. We propose that this atomic component arises, self-consistently, from the dissociated gas at the apex of the leading bow shocks and the relatively long molecule reformation time. At least 20 bow shocks are required in each lobe, although these may be sub-divided into smaller bows and turbulent shocked regions. The total outflow mechanical power and cooling amounts to over 30L_\odot, almost half the source's bolometric luminosity. Nevertheless, only about 6% of the clump mass has been set in outward motion by the outflow, allowing a collapse to continue.
A bipolar outflow from the massive protostellar core W51e2-E  [PDF]
Hui Shi,Jun-Hui Zhao,Jinlin Han
Physics , 2010, DOI: 10.1088/2041-8205/718/2/L181
Abstract: We present high resolution images of the bipolar outflow from W51e2, which are produced from the Submillimeter Array archival data observed for CO(3-2) and HCN(4-3) lines with angular resolutions of 0.8" x 0.6" and 0.3" x 0.2", respectively. The images show that the powerful outflow originates from the protostellar core W51e2-E rather than from the ultracompact HII region W51e2-W. The kinematic timescale of the outflow from W51e2-E is about 1000 yr, younger than the age (~5000 yr) of the ultracompact HII region W51e2-W. A large mass loss rate of ~1 x 10^{-3} M_sun yr^{-1} and a high mechanical power of 120 L_sun are inferred, suggesting that an O star or a cluster of B stars are forming in W51e2-E. The observed outflow activity along with the inferred large accretion rate indicates that at present W51e2-E is in a rapid phase of star formation.
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