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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 (NJ = 56-45) emission at ~25 resolution with the Submillimeter Array. A dust core is seen in the continuum around th...
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... observations Observations in 1.33 mm continuum, 12 CO (J = 2 − 1), 13 CO (J = 2−1), C 18 O (J = 2−1), and SO (J K = 6 5 −5 4 ) emission toward the IRAS source and the H 2 jet were made between 2004 November and 2005 March on top of Mauna Kea with the SMA in the compact configuration (see Table 1). Seven antennas were used in the array, giving baselines with projected lengths ranging from 14.1 to 136 m, result- ing in a synthesized beam (with natural weighting) with a size of 2.8 ′′ ×2.4 ′′ at 230 GHz. ...
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HH 212 is a Class 0 protostellar system found to host a "hamburger"-shaped dusty disk with a rotating disk atmosphere and a collimated SiO jet at a distance of ~ 400 pc. Recently, a compact rotating outflow has been detected in SO and SO2 toward the center along the jet axis at ~ 52 au (0.13") resolution. Here we resolve the compact outflow into a...
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Context. Herschel observations have emphasized the role of molecular filaments in star formation. However, the origin and evolution of these filaments are not yet well understood, partly because of the lack of kinematic information.
Aims. We confirm from a kinematic viewpoint that the Taurus B211/B213 filament is accreting background cloud material...
Citations
... A series of these velocity spurs composes a jagged PV profile sometimes called the "Hubble wedge" (Arce & Goodman 2001). These complex PV diagrams have been investigated in about a dozen low-mass Class 0 protostars so far, including HH111 (Cernicharo & Reipurth 1996), L1551 (Bachiller et al. 1994), L1157 (Gueth et al. 1998), HH212 (Lee et al. 2006), HH46-47 (Arce et al. 2013), and more recently Cepheus E (de Schutzer et al. 2022). ...
Variable accretion has been well studied in the evolved stages of low-mass star formation. However, the accretion history in the initial phases of star formation is still a seldom studied topic. The outflows and jets emerging from protostellar objects could shed some light on their accretion history. We consider the recently studied case of W43-MM1, a protocluster containing 46 outflows driven by 27 protostellar cores. The outflow kinematics of the individual cores and associated knots in W43-MM1 indicate episodic protostellar ejection. We take the observed parameters of an individual core system (core #8) and perform 3D hydrodynamic simulations of such a system, including episodic changes in the velocity of the outflow. The simulations consist of a collimated jet emerging from a core, taking into account one- and two-velocity modes in the variation of the ejection velocity of the jet. In addition, we investigated the effect of including the precession of the jet in the one- and two-velocity-mode models. From the simulations, we constructed position–velocity diagrams and compared them with the observations. We find that including a second mode in the ejection velocity, as well as the precession, are required to explain the positions of the outflow knots and other position–velocity features observed in core #8 in W43-MM1.
... Source A and Source B are not resolved. xxii Lee et al. (2006). Estimated from T dust . ...
The chemical diversity of low-mass protostellar sources has so far been recognized, and environmental effects are invoked as its origin. In this context, observations of isolated protostellar sources without the influence of nearby objects are of particular importance. Here, we report the chemical and physical structures of the low-mass Class 0 protostellar source IRAS 16544−1604 in the Bok globule CB 68, based on 1.3 mm Atacama Large Millimeter/submillimeter Array observations at a spatial resolution of ∼70 au that were conducted as part of the large program FAUST. Three interstellar saturated complex organic molecules (iCOMs), CH 3 OH, HCOOCH 3 , and CH 3 OCH 3 , are detected toward the protostar. The rotation temperature and the emitting region size for CH 3 OH are derived to be 131 ± 11 K and ∼10 au, respectively. The detection of iCOMs in close proximity to the protostar indicates that CB 68 harbors a hot corino. The kinematic structure of the C ¹⁸ O, CH 3 OH, and OCS lines is explained by an infalling–rotating envelope model, and the protostellar mass and the radius of the centrifugal barrier are estimated to be 0.08–0.30 M ⊙ and <30 au, respectively. The small radius of the centrifugal barrier seems to be related to the small emitting region of iCOMs. In addition, we detect emission lines of c-C 3 H 2 and CCH associated with the protostar, revealing a warm carbon-chain chemistry on a 1000 au scale. We therefore find that the chemical structure of CB 68 is described by a hybrid chemistry. The molecular abundances are discussed in comparison with those in other hot corino sources and reported chemical models.
... HH 212 is a young accreting protostellar system with a highly collimated spinning jet (Zinnecker et al. 1998;Lee et al. 2017a) in the Class 0 phase in Orion at a distance of ∼400 pc. With a nearly edge-on and vertically resolved disk (Lee et al. 2017b) deeply embedded in a dense rotating molecular core (Wiseman et al. 2001) and an infalling-rotating flattened envelope (Lee et al. 2006(Lee et al. , 2014, the disk formation and accretion process in the earliest phase of star formation has become a textbook case to study. The disk is rotationally supported, surrounding a protostar with a mass of ∼0.25 M e (Codella et al. 2014;Lee et al. 2017c). ...
We report the results of new dust polarization of a nearly edge-on disk in the HH 212 protostellar system, obtained with the Atacama Large Millimeter/submillimeter Array at ∼0.035″ (14 au) resolution in a continuum at λ ∼ 878 μ m. Dust polarization is detected within ∼44 au of the central source, where a rotationally supported disk has formed. The polarized emission forms V-shaped structures opening to the east, and probably to the west, arising from the disk surfaces and arm structures further away in the east and west, which could be due to potential spiral arms excited in the outer disk. The orientations of the polarization are mainly parallel to the minor axis of the disk, with some in the western part tilting slightly away from the minor axis to form a concave shape with respect to the center. This tilting of the orientations of the polarization is expected from dust self-scattering, e.g., by 50−75 μ m grains in a young disk. The intensity and degree of the polarization both peak near the central source with a small dip at the central source and decrease toward the edges. These decreases in the intensity and degree of polarization are expected from dichroic extinction by grains aligned by poloidal fields, but may also be consistent with dust self-scattering if the grain size decreases toward the edges. It is possible that both mechanisms are needed to produce the observed dust polarization, suggesting the presence of both grain growth and poloidal fields in the disk.
... The HH 211 outflow from Perseus is one of the youngest outflow/molecular jets, with a mass of 0.06 M e (Gueth & Guilloteau 1999;Hirano et al. 2006;Palau et al. 2006;Lee et al. 2009Lee et al. , 2014bLee et al. , 2018c, whose SiO jet was found to originate from within 0.03 auof the central protostar (Lee et al. 2009). HH 212, from Orion, is slightly more evolved with a higher central mass of ≈0.2 M e , which drives a symmetric jet in molecular hydrogen (Zinnecker et al. 1998;Lee et al. 2000Lee et al. , 2006Lee et al. , 2007Lee et al. , 2008Lee et al. , 2014aLee et al. , 2018b) whose SiO jet was from within 0.05 auof the protostar (Lee et al. 2008(Lee et al. , 2018b. Radii of launch from both systems, taken from rotation measurements, have been shown to be consistent with the X-wind model (Shu et al. 1994a(Shu et al. , 2000Shang et al. 1998;Cai et al. 2008;Lee et al. 2008Lee et al. , 2009Lee et al. , 2018bLee et al. , 2018c. ...
Large-scale morphology and time evolution are investigated for the unified model of bipolar outflows outlined in Shang et al. (2006), where an outflow forms by a radially directed, wide-angle magnetized wind interacting with magnetized isothermal toroids in various quasistatic states. The primary wide-angle wind is toroidally magnetized and maintains a cylindrically stratified density profile, mimicking the asymptotic solution of the cold X-wind model. We explore the interplay between the toroidally magnetized primary wind and the surrounding toroids threaded by poloidal magnetic fields and examine how the jet and shell morphology and fine structures within them vary with the physical parameters. The variation in flatness of the density distribution in the ambient isothermal toroids helps shape the varieties of lobe morphology and collimation. The presence of a stronger ambient poloidal field helps shape the outflow, forming a magnetic cocoon and nested multilayered cavities surrounding the wind-filled lobe, which is most evident in the more open configurations of the ambient toroids. The wind–toroid interface is prone to substantial shear and thus unstable to the Kelvin–Helmholtz instability. Magnetic forces in the compressed toroidally magnetized high-velocity wind can generate vorticity, leading to nonlinear patterns within the extended magnetized mixing layers. Magnetic disturbances generated by the interplay could modulate lobe shapes, density, and velocities, giving rise to visual impressions of thicker and rugged shells and apparent episodic distribution of matter. The system maintains a quasi-self-similar evolution in time, which serves as a proxy for understanding the underlying physical mechanisms driving it.
... It is located in the L1630 cloud in Orion at a distance of about 400 pc (Kounkel et al. 2017). Images of continuum, CO, and HCO+ reveal a flattened, massive envelope (∼0.06−0.1 M ) around the central source, leaving little doubt that it is a very young system that is still in active formation (Lee et al. 2006(Lee et al. , 2008(Lee et al. , 2014. One of the most important features of the HH 212 system that makes it ideal for our purposes of constraining dust opacities is its nearly edge-on orientation and the dark lane along the disc equatorial plane observed by Lee et al. (2017b) in the Atacama Large Millimetre/submillimetre Array (ALMA) band 7 (λ = 0.85 mm, 0.02 arcsec resolution), which demonstrated unequivocally that the disc is optically thick along sightlines close to the centre and becomes optically thin near the outer edge. ...
(Sub)millimeter dust opacities are required for converting the observable dust continuum emission to the mass, but their values have long been uncertain, especially in disks around young stellar objects. We propose a method to constrain the opacity κν in edge-on disks from a characteristic optical depth τ0, ν, the density ρ0 and radius R0 at the disk outer edge through κν = τ0, ν/(ρ0R0) where τ0, ν is inferred from the shape of the observed flux along the major axis, ρ0 from gravitational stability considerations, and R0 from direct imaging. We applied the 1D semi-analytical model to the embedded, Class 0, HH 212 disk, which has high-resolution data in ALMA Band 9, 7, 6, and 3 and VLA Ka band (λ=0.43, 0.85, 1.3, 2.9, and 9.1 mm). The modeling is extended to 2D through RADMC-3D radiative transfer calculations. We find a dust opacity of κν ≈ 1.9 × 10−2, 1.3 × 10−2, and 4.9 × 10−3cm2 per gram of gas and dust for ALMA Bands 7, 6, and 3, respectively with uncertainties dependent on the adopted stellar mass. The inferred opacities lend support to the widely used prescription κλ = 2.3 × 10−2(1.3mm/λ) cm2 g−1 . We inferred a temperature of ∼45 K at the disk outer edge which increases radially inward. It is well above the sublimation temperatures of ices such as CO and N2, which supports the notion that the disk chemistry cannot be completely inherited from the protostellar envelope.
... It is located in the L1630 cloud in Orion at a distance of about 400 pc (Kounkel et al. 2017). Images of continuum, CO, and HCO+ reveal a massive, flattened envelope around the central source (Lee et al. 2006(Lee et al. , 2008(Lee et al. , 2014, leaving little doubt that it is a very young system that is still in active formation. One of the most important features of the HH 212 system that make it ideal for our purposes of constraining dust opacities is its nearly edge-on orientation and the dark lane along the disk equatorial plane observed by Lee et al. (2017b) in the Atacama Large Millimeter/submillimeter Array (ALMA) Band 7 (λ = 0.85 mm, 0.02 resolution), which demonstrated unequivocally that the disk is optically thick along sight lines close to the center and becomes optically thin near the outer edge. ...
(Sub)millimeter dust opacities are required for converting the observable dust continuum emission to the mass, but their values have long been uncertain, especially in disks around young stellar objects. We propose a method to constrain the opacity $\kappa_\nu$ in edge-on disks from a characteristic optical depth $\tau_{0,\nu}$, the density $\rho_0$ and radius $R_0$ at the disk outer edge through $\kappa_\nu=\tau_{0,\nu}/(\rho_0 R_0)$ where $\tau_{0,\nu}$ is inferred from the shape of the observed flux along the major axis, $\rho_0$ from gravitational stability considerations, and $R_0$ from direct imaging. We applied the 1D semi-analytical model to the embedded, Class 0, HH 212 disk, which has high-resolution data in ALMA Band 9, 7, 6, and 3 and VLA Ka band ($\lambda$=0.43, 0.85, 1.3, 2.9, and 9.1 mm). The modeling of the HH 212 disk is extended to 2D through RADMC-3D radiative transfer calculations. We find a dust opacity of $\kappa_\nu \approx $ $1.9\times 10^{-2}$, $1.3\times 10^{-2}$, and $4.9\times 10^{-3}$ cm$^2$ per gram of gas and dust for ALMA Bands 7, 6, and 3, respectively with uncertainties dependent on the adopted stellar mass. The inferred opacities lend support to the widely used prescription $\kappa_\lambda=2.3\times 10^{-2} (1.3 {\rm mm}/\lambda)$ cm$^2$ g$^{-1}$ advocated by Beckwith et al. (1990). We inferred a temperature of ~45K at the disk outer edge which increases radially inward. It is well above the sublimation temperatures of ices such as CO and N$_2$, which supports the notion that the disk chemistry cannot be completely inherited from the protostellar envelope.
... The closest region of star formation to HH212 is the OriB9 region to the southwest (see Figure 9 of Miettinen 2012). The driving source of HH212 is IRAS05413-0104, a Class0 source embedded in a cloud core that is flattened and rotating perpendicular to the jet flow axis (Wiseman et al. 2001;Lee et al. 2006Lee et al. , 2014. The HH 212 jet has been observed in the infrared in the principal H 2 transition at 2.212 μm by Davis et al. (2000), Smith et al. (2007), and Correia et al. (2009). ...
... From radial velocities and proper motions, the water masers are found to move along the jet axis, and Claussen et al. (1998) deduced that the outflow axis lies within 5°of the plane of the sky. The jet was studied in SiO by Takami et al. (2006), Codella et al. (2007), and Cabrit et al. (2007Cabrit et al. ( , 2012, and the associated molecular outflow has been studied in detail by Lee et al. (2000Lee et al. ( , 2006Lee et al. ( , 2007Lee et al. ( , 2008Lee et al. ( , 2015, Codella et al. (2014Codella et al. ( , 2016, and Leurini et al. (2016). ALMA observations have revealed an accretion disk , Lee et al. 2017a, 2017b, 2018a and have been used to explore the jet launching region and an associated disk wind (Podio et al. 2015;Codella et al. 2016;Tabone et al. 2017;Lee et al. 2018b;Sahu et al. 2018). ...
... Information technology-based transaction otherwise known as e-commerce enables instant access across the globe. However, the success of e-commerce lies much on the effective functioning of telecommunication infrastructure (Lee, Ho et al. 2006) Integration of e-commerce into a functioning organization leads to the restructuring of the entire business setting. Other barriers such as payment method, deliveries of finished goods, insecure credit cards billing and insufficient knowledge of the service cost contends with the technological advances in e-commerce adoption(Mohamed Ahmed A.Said 2013). ...
— Hospitality industry is the main service sector in most developed countries and developing countries in the global economy. At present many
of the hotels have implemented e-commerce to their business models and gained great advantages and increased profitability. This study aims to
examine the impact of top management support and e-commerce usage on business performance of the hospitality industry in general and hotels in
Libya in particular. A wide range of approaches have been applied in the hotel industry in Libya, especially those hotels that have the practices and
experiences with previous e-commerce. The results shows that small and medium size firms in hospitality industry in Libya are confronting similar
challenges and obstacles to other small businesses when utilizing e-commerce .The sample was drawn by using stratified random sampling. Key
informant discussions and focus group discussions were conducted to gain further insight into the findings. Descriptive and inferential (Frequencies,
Means, Standard Deviation, and Correlation Matrix) statistical analysis were done by using the SPSS software
... Likewise in the north (Figure 2(b)), a similar wideopening shell is seen opening to the north, connecting to the big bow shock NB3 farther out. These wide-opening shells are also seen in the lower transition line of CO at J = 2 − 1 (Lee et al. 2006), likely tracing the outflow cavity walls consisting mainly of the ambient material swept up by the big bow shocks. At the base around the central source (see the zoomedin area inFigure 3(c)), the shells fit right into the bay of the flattened envelope detected in the 350 GHz continuum (Lee et al. 2014). ...
HH 212 is a nearby (400 pc) highly collimated protostellar jet powered by a
Class 0 source in Orion. We have mapped the inner 80" (~ 0.16 pc) of the jet in
SiO (J=8-7) and CO (J=3-2) simultaneously at ~ 0.5 resolution with the Atacama
Millimeter/Submillimeter Array at unprecedented sensitivity. The jet consists
of a chain of knots, bow shocks, and sinuous structures in between. As compared
to that seen in our previous observations with the Submillimeter Array, it
appears to be more continuous, especially in the northern part. Some of the
knots are now seen associated with small bow shocks, with their bow wings
curving back to the jet axis, as seen in pulsed jet simulations. Two of them
are reasonably resolved, showing kinematics consistent with sideways ejection,
possibly tracing the internal working surfaces formed by a temporal variation
in the jet velocity. In addition, nested shells are seen in CO around the jet
axis connecting to the knots and bow shocks, driven by them. The proper motion
of the jet is estimated to be ~ 115+-50 km/s, comparing to our previous
observations. The jet has a small semi-periodical wiggle, with a period of ~ 93
yrs. The amplitude of the wiggle first increases with the distance from the
central source and then stays roughly constant. One possible origin of the
wiggle could be the kink instability in a magnetized jet.
... For such non-axisymmetric envelope structures, it is not straightforward to disentangle between the gas structures and kinematics (Tobin et al. 2012a). On the other hand, on smaller scales of ∼1000 AU, the envelope structures appear to be more or less symmetric (Tobin et al. 2011(Tobin et al. , 2012a(Tobin et al. , 2012b, and previous observations of Class 0 and I sources without sizable Keplerian disks with radii of hundreds of AU, such as B335 (Yen et al. 2010), HH 212 (Lee et al. 2006), L1527 IRS (Ohashi et al. 1997), L1551 IRS 5 (Momose et al. 1998), and IRAS 16293−2422 (Takakuwa et al. 2007), show that the kinematics of their protostellar envelopes on a 1000 AU scale can be explained by axisymmetric models of infalling and rotational motions. On the other hand, our ALMA observations show that in L1489 IRS, which is more evolved than the sources mentioned above, on a 1000 AU scale the infalling material is primarily from the two directions (north and south) and cannot be reproduced by an axisymmetric model. ...
We have conducted ALMA observations in the 1.3 mm continuum and 12CO (2-1),
C18O (2-1) and SO (5_6-4_5) lines toward L1489 IRS, a Class I protostar
surrounded by a Keplerian disk and an infalling envelope. The Keplerian disk is
clearly identified in the 12CO and C18O emission, and its outer radius (~700
AU) and mass (~0.005 Msun) are comparable to those of disks around T Tauri
stars. The protostellar mass is estimated to be 1.6 Msun with the inclination
angle of 66 deg. In addition to the Keplerian disk, there are blueshifted and
redshifted off-axis protrusions seen in the C18O emission pointing toward the
north and the south, respectively, adjunct to the middle part of the Keplerian
disk. The shape and kinematics of these protrusions can be interpreted as
streams of infalling flows with a conserved angular momentum following
parabolic trajectories toward the Keplerian disk, and the mass infalling rate
is estimated to be ~5E-7 Msun/yr. The specific angular momentum of the
infalling flows (~2.5E-3 km/s*pc) is comparable to that at the outer radius of
the Keplerian disk (~4.8E-3 km/s*pc). The SO emission is elongated along the
disk major axis and exhibits a linear velocity gradient along the axis, which
is interpreted as that the SO emission primarily traces a ring region in the
flared Keplerian disk at radii of ~250-390 AU. The local enhancement of the SO
abundance in the ring region can be due to the accretion shocks at the
centrifugal radius where the infalling flows fall onto the disk. Our ALMA
observations unveiled both the Keplerian disk and the infalling gas onto the
disk, and the disk can further grow by accreting material and angular momenta
from the infalling gas.
