We investigate the driving mechanism of outflows and jets in star formation process using resistive MHD nested grid simulations. We found two distinct flows in the collapsing cloud core: Low-velocity outflows (sim 5 km/s) with a wide opening angle, driven from the first adiabatic core, and high-velocity jets (sim 50 km/s) with good collimation, driven from the protostar. High-velocity jets are enclosed by low-velocity outflow. The difference in the degree of collimation between the two flows is caused by the strength of the magnetic field and configuration of the magnetic field lines. The magnetic field around an adiabatic core is strong and has an hourglass configuration. Therefore, the low-velocity outflow from the adiabatic core are driven mainly by the magnetocentrifugal mechanism and guided by the hourglass-like field lines. In contrast, the magnetic field around the protostar is weak and has a straight configuration owing to Ohmic dissipation in the high-density gas region. Therefore, high-velocity jet from the protostar are driven mainly by the magnetic pressure gradient force and guided by straight field lines. Differing depth of the gravitational potential between the adiabatic core and the protostar cause the difference of the flow speed. Low-velocity outflows correspond to the observed molecular outflows, while high-velocity jets correspond to the observed optical jets. We suggest that the protostellar outflow and the jet are driven by different cores (the first adiabatic core and protostar), rather than that the outflow being entrained by the jet.
The multiple protostellar system L1551 IRS5 exhibits a large-scale bipolar molecular outflow. We have studied this outflow within ~4000 AU of its driving source(s) with the SubMillimeter Array. Our CO(2-1) image at ~4" (~560 AU) resolution reveals three distinct components: 1) an X-shaped structure spanning ~20" from center with a similar symmetry axis and velocity pattern as the large-scale outflow; 2) an S-shaped structure spanning ~10" from center also with an opposite velocity pattern to the large-scale outflow; and 3) a compact central component spanning ~1.4" from center again with a sim…
The evolution of protostellar outflow is investigated with resistive magneto-hydrodynamic nested-grid simulations that cover a wide range of spatial scales (\sim 1AU - 1pc). We follow cloud evolution from the pre-stellar core stage until the infalling envelope dissipates long after the protostar formation. We also calculate protostellar evolution to derive protostellar luminosity with time-dependent mass accretion through a circumstellar disk. The protostellar outflow is driven by the first core prior to protostar formation and is directly driven by the circumstellar disk after protostar forma…
We report the results of a numerical study on the initial formation stages of low-mass protostellar binary systems. We determine the separation of protostellar binaries formed as a function of the initial thermal state by varying the initial temperature in a slightly modified version of the Burkert and Bodenheimer collapse test. We find that the outcome is highly sensitive to both the initial temperature of the cloud and the initial amplitude of azimuthal density perturbation A. For A=10 %, variations of only 1 unit Kelvin below 10 K lead to changes of up to 100 AU ( i.e. of order 30 %) in the…
Star formation efficiency controlled by the protostellar outflow in a single cloud core is investigated by three-dimensional resistive MHD simulations. Starting from the prestellar cloud core, the star formation process is calculated until the end of the main accretion phase. In the calculations, the mass of the prestellar cloud is parameterized. During the star formation, the protostellar outflow is driven by the circumstellar disk. The outflow extends also in the transverse direction until its width becomes comparable to the initial cloud scale, and thus, the outflow has a wide opening angle…
We present SOFIA/FIFI-LS observations of three Class 0 and one Class I outflows (Cep E, HH 1, HH 212, and L1551 IRS5) in the far-infrared [O I]63mum and [O I]145mum transitions. Spectroscopic [O I]63mum maps enabled us to infer the spatial extent of warm, low-excitation atomic gas within these protostellar outflows. If proper shock conditions prevail, the instantaneous mass-ejection rate is directly connected to the [O I]63mum luminosity. In order to unravel evolutionary trends, we analysed a set of 14 Class 0/I outflow sources that were spatially resolved in the [O I]63mum emission. We compar…
We present results from three-dimensional, self-gravitating, radiation-hydrodynamic simulations of low-mass protostellar outflows. We construct synthetic observations in 12CO in order to compare with observed outflows and evaluate the effects of beam resolution and outflow orientation on inferred outflow properties. To facilitate the comparison, we develop a quantitative prescription for measuring outflow opening angles. Using this prescription, we demonstrate that, in both simulations and synthetic observations, outflow opening angles broaden with time similarly to observed outflows. However,…
We report the results of a series of AMR radiation-hydrodynamic simulations of the collapse of massive star forming clouds using the ORION code. These simulations are the first to include the feedback effects protostellar outflows, as well as protostellar radiative heating and radiation pressure exerted on the infalling, dusty gas. We find that that outflows evacuate polar cavities of reduced optical depth through the ambient core. These enhance the radiative flux in the poleward direction so that it is 1.7 to 15 times larger than that in the midplane. As a result the radiative heating and out…
We carry out radiation hydrodynamical simulations of the formation of massive stars in the super-Eddington regime including both their radiative feedback and protostellar outflows. The calculations start from a prestellar core of dusty gas and continue until the star stops growing. The accretion ends when the remnants of the core are ejected, mostly by the force of the direct stellar radiation in the polar direction and elsewhere by the reradiated thermal infrared radiation. How long the accretion persists depends on whether the protostellar outflows are present. We set the mass outflow rate t…
We present and discuss \emph{Spitzer} and near-infrared H$_{2}$ observations of a new bi-polar protostellar outflow in the Rosette Molecular Cloud. The outflow is seen in all four IRAC bands and partially as diffuse emission in the MIPS 24 $μ$m band. An embedded MIPS 24 $μ$m source bisects the outflow and appears to be the driving source. This source is coincident with a dark patch seen in absorption in the 8 $μ$m IRAC image. \emph{Spitzer} IRAC color analysis of the shocked emission was performed from which thermal and column density maps of the outflow were constructed. Narrow-band near-infr…
The loss of mass from protostars, in the form of a jet or outflow, is a necessary counterpart to protostellar mass accretion. Outflow ejection events probably vary in their velocity and/or in the rate of mass loss. Such `episodic' ejection events have been observed during the Class 0 protostellar phase (the early accretion stage), and continue during the subsequent class I phase that marks the first one million years of star formation. Previously observed episodic-ejection sources were relatively isolated; however, the most common sites of star formation are clusters. Outflows link protostars …
Protostellar outflows provide a means to probe the accretion process of forming stars and their ability to inject energy into their surroundings. However, conclusions based on outflow observations depend upon the degree of accuracy with which their properties can be estimated. We examine the quality of Atacama Large Millimeter/submillimeter Array (ALMA) observations of protostellar outflows by producing synthetic $^{12}$CO(1-0) and $^{13}$CO(1-0) observations of numerical simulations. We use various ALMA configurations, observational parameters, and outflow inclinations to assess how accuratel…
We have searched the L1340 A, B, and C clouds for shocks from protostellar outflows using the H$_2$ 2.122 $μ$m near-IR line as a shock tracer. Substantial outflow activity has been found in each of the three regions of the cloud (L1340 A, L1340 B, & L1340 C). We find 42 distinct shock complexes (16 in L1340 A, 11 in L1340 B, and 15 in L1340 C). We were able to link 17 of those shock complexes in to 12 distinct outflows and identify candidate source stars for each. We examine the properties (A$_{V}$, T$_{bol}$, and L$_{bol}$) of the source protostars and compare that to the properties of the ge…
We investigate protostellar outflow evolution, gas entrainment, and star formation efficiency using radiation-hydrodynamic simulations of isolated, turbulent low-mass cores. We adopt an X-wind launching model, in which the outflow rate is coupled to the instantaneous protostellar accretion rate and evolution. We vary the outflow collimation angle from $θ$=0.01-0.1 and find that even well collimated outflows effectively sweep up and entrain significant core mass. The Stage 0 lifetime ranges from 0.14-0.19 Myr, which is similar to the observed Class 0 lifetime. The star formation efficiency of t…
We present observations of outflows in the star-forming region NGC 1333 using the Combined Array for Research in Millimeter-Wave Astronomy (CARMA). We combined the 12CO and 13CO (1-0) CARMA mosaics with data from the 14-m Five College Radio Astronomy Observatory (FCRAO) to probe the central, most dense and active region of this protostellar cluster at scales from 5'' to 7' (or 1000 AU to 0.5 pc at a distance of 235 pc). We map and identify 12CO outflows, and along with 13CO data we estimate their mass, momentum and energy. Within the 7'x7' map, the 5'' resolution allows for a detailed study of…
Protostellar feedback, both radiation and bipolar outflows, dramatically affects the fragmentation and mass accretion from star-forming cores. We use ORION, an adaptive mesh refinement gravito-radiation-hydrodynamics code, to simulate the formation of a cluster of low-mass stars, including both radiative transfer and protostellar outflows. We ran four simulations to isolate the individual effects of radiation feedback and outflow feedback as well as the combination of the two. Outflows reduce protostellar masses and accretion rates each by a factor of three and therefore reduce protostellar lu…
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…
Efficient magnetic braking is a formidable obstacle to the formation of rotationally supported disks (RSDs) around protostars in magnetized dense cores. We have previously shown, through 2D (axisymmetric) non-ideal MHD simulations, that removing very small grains (VSGs: ~10 Å$~$to few 100 Å) can greatly enhance ambipolar diffusion and enable the formation of RSDs. Here we extend the simulations of disk formation enabled by VSG removal to 3D. We find that the key to this scenario of disk formation is that the drift velocity of the magnetic field almost cancels out the infall velocity of the neu…
A protostellar jet and outflow are calculated for \sim 270 yr following the protostar formation using a three dimensional magnetohydrodynamics simulation, in which both the protostar and its parent cloud are spatially resolved. A high-velocity (\sim100km/s) jet with good collimation is driven near the disk's inner edge, while a low-velocity (<10km/s) outflow with a wide opening angle appears in the outer-disk region. The high-velocity jet propagates into the low-velocity outflow, forming a nested velocity structure in which a narrow high-velocity flow is enclosed by a wide low-velocity flow. T…
The collapse of the magnetic rotating protostellar cloud with mass of $10\,M_{\odot}$ is numerically studied. The initial ratios of the thermal, magnetic, and rotational energies of the cloud to the modulus of its gravitational energy are 0.3, 0.2 and 0.01, respectively. The emphasis is on the evolution and properties of the quasi-magnetostatic primary disk formed at the isothermal stage of the collapse. Simulations show that the primary disk size and mass increase during evolution from $1500$ au to $7400$ au and from $0.3\,M_{\odot}$ to $5.2\,M_{\odot}$, respectively. Magnetic field is quasi-…
The protostellar collapse of a molecular cloud core is usually accompanied by outflow phenomena. The latter are thought to be driven by magnetorotational processes from the central parts of the protostellar disc. While several 3D AMR/nested grid studies of outflow phenomena in collapsing magnetically supercritical dense cores have been reported in the literature, so far no such simulation has been performed using the Smoothed Particle Hydrodynamics (SPH) method. This is mainly due to intrinsic numerical difficulties in handling magnetohydrodynamics within SPH, which only recently were partly r…
To study the role of protosellar jets and outflows in the time evolution of the parent cores and the protostars, the astronomical community needs a large enough data base of infrared images of protostars at the highest spatial resolution possible, to reveal the details of their morphology. Spitzer provides unprecedented sensitivity in the infrared to study both the jet and outflow features, however its spatial resolution is limited by its 0.85m mirror. Here we use a high resolution deconvolution algorithm, "HiRes", to improve the visualization of spatial morphology by enhancing resolution (to …
The formation of stars is usually accompanied by the launching of protostellar outflows. Observations with the Atacama Large Millimetre/sub-millimetre Array (ALMA) will soon revolutionalise our understanding of the morphologies and kinematics of these objects. In this paper, we present synthetic ALMA observations of protostellar outflows based on numerical magnetohydrodynamic collapse simulations. We find significant velocity gradients in our outflow models and a very prominent helical structure within the outflows. We speculate that the disk wind found in the ALMA Science Verification Data of…
In star formation, magnetic fields act as a cosmic angular momentum extractor that increases mass accretion rates onto protostars and in the process, creates spectacular outflows. However, recently it has been argued that this magnetic brake is so strong that early protostellar disks -- the cradles of planet formation -- cannot form. Our three-dimensional numerical simulations of the early stages of collapse (\lesssim 10^5 yr) of overdense star--forming clouds form early outflows and have magnetically regulated and rotationally dominated disks (inside 10 AU) with high accretion rates, despite …
The protostellar outflows have indispensable role in the formation of single stars, because they carry off the excess angular momentum from the centre of the shrinking gas cloud, and permits further collapse to form a star. On the other hand, a significant fraction of stars is supposed to be born as binaries with circumbinary disk that are frequently observed. Here, we investigate the evolution of a magnetized rotating cloud using three-dimensional resistive MHD nested-grid code, and show that the outflow is driven by the circumbinary disk and has an important role even in the binary formation…
We have developed a modified form of the equations of smoothed particle magnetohydrodynamics which are stable in the presence of very steep density gradients. Using this formalism, we have performed simulations of the collapse of magnetised molecular cloud cores to form protostars and drive outflows. Our stable formalism allows for smaller sink particles (< 5 AU) than used previously and the investigation of the effect of varying the angle, θ, between the initial field axis and the rotation axis. The nature of the outflows depends strongly on this angle: jet-like outflows are not produced at a…
We examine emission from a young protostellar object (YPO) with three-dimensional ideal MHD simulations and three-dimensional non-local thermodynamic equilibrium (non-LTE) line transfer calculations, and show the first results. To calculate the emission field, we employed a snapshot result of an MHD simulation having young bipolar outflows and a dense protostellar disk (a young circumstellar disk) embedded in an infalling envelope. Synthesized line emission of two molecular species (CO and SiO) show that subthermally excited SiO lines as a high density tracer can provide a better probe of the …
Young stars are associated with prominent outflows of molecular gas. The ejection of gas via these outflows is believed to remove angular momentum from the protostellar system, thus permitting young stars to grow by accretion of material from the protostellar disk. The underlying mechanism for outflow ejection is not yet understood, but is believed to be closely linked to the protostellar disk. Assorted scenarios have been proposed to explain protostellar outflows; the main difference between these models is the region where acceleration of material takes place: close to the protostar itself (…
We identify 45 protostellar outflows in CO maps of the Orion A giant molecular cloud from the CARMA-NRO Orion survey. Our sample includes 11 newly detected outflows. We measure the mass and energetics of the outflows, including material at low-velocities by correcting for cloud contributions. The total momentum and kinetic energy injection rates of outflows is comparable to the turbulent dissipation rate of the cloud. We also compare the outflow position angles to the orientation of C$^{18}$O filaments. We find that the full sample of outflows is consistent with being randomly oriented with re…
Protostellar outflow is a prominent process that accompanies the formation of stars. It is generally agreed that wide-angled protostellar outflows come from the interaction between the wind from a forming star and the ambient gas. However, it is still unclear how the interaction takes place. In this work, we theoretically investigate the possibility that the outflow results from interaction between the wind and the ambient gas in the form of turbulent entrainment. In contrast to the previous models, turbulent motion of the ambient gas around the protostar is taken into account. In our model, t…
Turbulent entrainment processes may play an important role in the outflows from young stellar objects at all stages of their evolution. In particular, lateral entrainment of ambient material by high-velocity, well-collimated protostellar jets may be the cause of the multiple emission-line velocity components observed in the microjet-scale outflows driven by classical T Tauri stars. Intermediate-velocity outflow components may be emitted by a turbulent, shock- excited mixing layer along the boundaries of the jet. We present a formalism for describing such a mixing layer based on Reynolds decomp…
Outflows and jets are intimately related to the formation of stars, and play an important role in redistributing mass, energy and angular momentum within the dense core and parent cloud. The interplay between magnetic field and rotation is responsible for launching these outflows, whose formation has been generally carried out for idealized systems where the angle $α$ between the rotation axis and large-scale magnetic field is zero. Here we explore, through three-dimensional ideal magneto-hydrodynamic simulations, the effects of a non-zero $α$ on the formation of outflows during the collapse o…
The formation and evolution of a circumstellar disk in magnetized cloud cores is investigated from prestellar core stage until sim 10^4 yr after protostar formation. In the circumstellar disk, fragmentation first occurs due to gravitational instability in a magnetically inactive region, and substellar-mass objects appear. The substellar-mass objects lose their orbital angular momenta by gravitational interaction with the massive circumstellar disk and finally fall onto the protostar. After this fall, the circumstellar disk increases its mass by mass accretion and again induces fragmentation. T…
We investigate protostellar collapse of molecular cloud cores by numerical simulations, taking into account turbulence and magnetic fields. By using the adaptive mesh refinement technique, the collapse is followed over a wide dynamic range from the scale of a turbulent cloud core to that of the first core. The cloud core is lumpy in the low density region owing to the turbulence, while it has a smooth density distribution in the dense region produced by the collapse. The shape of the dense region depends mainly on the mass of the cloud core; a massive cloud core tends to be prolate while a les…
Recent observations uncover various phenomena around the protostar such as misalignment between the outflow and magnetic field, precession of the jet, and time variability of the ejected clumps, whose origins are under debate. We perform a three-dimensional resistive magnetohydrodynamics simulation of the protostar formation in a star-forming core whose rotation axis is tilted at an angle $45^\circ$ with respect to the initial magnetic field, in which the protostar is resolved with a spatial resolution of $0.01\,$au. In low-dense outer region, the prestellar core contracts along the magnetic f…
The star-forming efficiency of dense gas is thought to be set within cores by outflow and radiative feedback. We use magneto-hydrodynamic simulations to investigate the relation between protostellar outflow evolution, turbulence and star formation efficiency. We model the collapse and evolution of isolated dense cores for $\gtrsim$ 0.5 Myr including the effects of turbulence, radiation transfer, and both radiation and outflow feedback from forming protostars. We show that outflows drive and maintain turbulence in the core environment even with strong initial fields. The star-formation efficien…
We discuss the role of protostellar outflow feedback in clustered star formation using the observational data of recent molecular outflow surveys toward nearby cluster-forming clumps. We found that for almost all clumps, the outflow momentum injection rate is significantly larger than the turbulence dissipation rate. Therefore, the outflow feedback is likely to maintain supersonic turbulence in the clumps. For less massive clumps such as B59, L1551, and L1641N, the outflow kinetic energy is comparable to the clump gravitational energy. In such clumps, the outflow feedback probably affects sign…
A massive envelope and a strong bipolar outflow are the two main structures characterizing the youngest protostellar systems. In order to understand the physical properties of a bipolar outflow and the relationship with those of the envelope, we obtained a mosaic map covering the whole bipolar outflow of the youngest protostellar system L1157 with about $5"$ angular resolution in CO J=2-1 using the Combined Array for Research in Millimeter-wave Astronomy. By utilizing these observations of the whole bipolar outflow, we estimate its physical properties and show that they are consistent with mul…
The evolution of protostellar outflows is investigated under different mass accretion rates in the range $\sim10^{-5}-10^{-2} {\rm M}_\odot$ yr$^{-1}$ with three-dimensional magnetohydrodynamic simulations. A powerful outflow always appears in strongly magnetized clouds with $B_0 \gtrsim B_{\rm 0, cr}$ $=10^{-4} (M_{\rm cl}/100 {\rm M}_\odot){\rm G}$, where $M_{\rm cl}$ is the cloud mass. When a cloud has a weaker magnetic field, the outflow does not evolve promptly with a high mass accretion rate. In some cases with moderate magnetic fields $B_0$ slightly smaller than $B_{\rm 0,cr}$, the outf…
HH 900 is a peculiar protostellar outflow emerging from a small, tadpole-shaped globule in the Carina nebula. Previous Hα imaging with HST/ACS showed an ionized outflow with a wide opening angle that is distinct from the highly collimated structures typically seen in protostellar jets. We present new narrowband near-IR [Fe II] images taken with the Wide Field Camera 3 on the Hubble Space Telescope that reveal a remarkably different structure than Hα. In contrast to the unusual broad Hα outflow, the [Fe II] emission traces a symmetric, collimated bipolar jet with the morphology and kinematics t…
With the recent recognition of a second, distinctive class of molecular outflows, namely the explosive ones not directly connected to the accretion-ejection process in the star formation, a juxtaposition of the morphological and kinematic properties of both classes is warranted. By applying the same method used in Zapata et al. (2009), and using $^{12}$CO(J=2-1) archival data from the Submillimeter Array (SMA), we contrast two well known explosive objects, Orion KL and DR21, to HH211 and DG Tau B, two flows representative of classical low-mass protostellar outflows. At the moment there are onl…
Stars form predominantly in clusters inside dense clumps of turbulent, magnetized molecular clouds. The typical size and mass of the cluster-forming clumps are \sim 1 pc and \sim 10^2 - 10^3 M_\odot, respectively. Here, we discuss some recent progress on theoretical and observational studies of clustered star formation in such parsec-scale clumps with emphasis on the role of protostellar outflow feedback. Recent simulations indicate that protostellar outflow feedback can maintain supersonic turbulence in a cluster-forming clump, and the clump can keep a virial equilibrium long after the initia…
The dense molecular clump P1 in the infrared dark cloud (IRDC) complex G28.34+0.06 harbors a massive protostellar cluster at its extreme youth. Our previous Submillimeter Array (SMA) observations revealed several jet-like CO outflows emanating from the protostars, indicative of intense accretion and potential interaction with ambient natal materials. Here we present the Expanded Very Large Array (EVLA) spectral line observations toward P1 in the NH3 (J,K) = (1,1), (2,2), (3,3) lines, as well as H2O and class I CH3OH masers. Multiple NH3 transitions reveal the heated gas widely spread in the 1 …
For a binary protostellar outflow system in which its members are located so close to each other (the separation being smaller than the addition of the widths of the flows) and with large opening angles, the collision seems unavoidable regardless of the orientation of the outflows. This is in contrast to the current observational evidence of just a few regions with indications of colliding outflows. Here, using sensitive observations of the Atacama Large Millimeter/Submillimeter Array (ALMA), we report resolved images of carbon monoxide (CO) towards the binary flows associated with the BHR71 p…
We perform two-dimensional axially symmetric radiation-hydrodynamic simulations to assess the impact of outflows and radiative force feedback from massive protostars by varying when the protostellar outflow starts, the ratio of ejection to accretion rates, and the strength of the wide angle disk wind component. The star formation efficiency, i.e. the ratio of final stellar mass to initial core mass, is dominated by radiative forces and the ratio of outflow to accretion rates. Increasing this ratio has three effects: First, the protostar grows slower with a lower luminosity at any given time, l…
We perform three dimensional smoothed particle hydrodynamics (SPH) simulations of gas accretion onto the seeds of binary stars to investigate their short-term evolution. Our simulation setup is more realistic compared to the previous works by taking into account of dynamically evolving envelope with non-uniform distribution of gas density and angular momentum of accreting flow. Our initial condition includes a seed binary and a surrounding gas envelope, modelling the phase of core collapse of gas cloud when the fragmentation has already occurred. We assume that the seed binary has no eccentric…
We report the results of spectroscopic mapping observations carried out toward protostellar outflows in the BHR71, L1157, L1448, NGC 2071, and VLA 1623 molecular regions using the Infrared Spectrograph (IRS) of the Spitzer Space Telescope. These observations, covering the 5.2 - 37 micron spectral region, provide detailed maps of the 8 lowest pure rotational lines of molecular hydrogen and of the [SI] 25.25 micron and [FeII] 26.0 micron fine structure lines. The molecular hydrogen lines, believed to account for a large fraction of the radiative cooling from warm molecular gas that has been heat…
We present results of 1.3 mm dust polarization observations toward 16 nearby, low-mass protostars, mapped with ~2.5" resolution at CARMA. The results show that magnetic fields in protostellar cores on scales of ~1000 AU are not tightly aligned with outflows from the protostars. Rather, the data are consistent with scenarios where outflows and magnetic fields are preferentially misaligned (perpendicular), or where they are randomly aligned. If one assumes that outflows emerge along the rotation axes of circumstellar disks, and that the outflows have not disrupted the fields in the surrounding m…
Molecular outflows driven by protostellar cluster members likely impact their surroundings and contribute to turbulence, affecting subsequent star formation. The very young Serpens South cluster consists of a particularly high density and fraction of protostars, yielding a relevant case study for protostellar outflows and their impact on the cluster environment. We combined CO $J=1-0$ observations of this region using the Combined Array for Research in Millimeter-wave Astronomy (CARMA) and the Institut de Radioastronomie Millimétrique (IRAM) 30 m single dish telescope. The combined map allows …
Observations of dense molecular gas lie at the basis of our understanding of the density and temperature structure of protostellar envelopes and molecular outflows. We aim to characterize the properties of the protostellar envelope, molecular outflow and surrounding cloud, through observations of high excitation molecular lines within a sample of 16 southern sources presumed to be embedded YSOs. Observations of submillimeter lines of CO, HCO+ and their isotopologues, both single spectra and small maps were taken with the FLASH and APEX-2a instruments mounted on APEX to trace the gas around the…
Molecular outflows are often detected originating from both protostellar and extragalactic sources. Studies of low-mass, isolated high-mass, and extragalactic sources reveal scaling relations connecting the force carried by an outflow and the properties of the source that drives it. The aim of this work is to examine the effects of clustered star formation on the protostellar outflows and their scaling relations and to explore the possibility that outflows varying greatly scale and energetics are consistent with being launched by the same physical processes. High-angular resolution CO J = 3-2 …
The pre-stellar cores in which low mass stars form are generally well magnetized. Our simulations show that early protostellar discs are massive and experience strong magnetic torques in the form of magnetic braking and protostellar outflows. Simulations of protostellar disk formation suggest that these torques are strong enough to suppress a rotationally supported structure from forming for near critical values of mass-to-flux. We demonstrate through the use of a 3D adaptive mesh refinement code -- including cooling, sink particles and magnetic fields -- that one produces transient 1000 AU di…
We have carried out 12CO J=2-1 and 12CO J=3-2 observations toward the high-mass protostellar candidate IRAS 20188+3928. Compared with previous observations, the 12CO J=2-1 and 12CO J=3-2 lines both have asymmetric profiles with an absorption dip. The velocity of the absorption dip is 1.0 km/s. The spectral shape may be caused by rotation. The velocity-integrated intensity map and position-velocity diagram of the 12CO J=2-1 line present an obvious bipolar component, further verifying that this region has an outflow motion. This region is also associated with an HII region, an IRAS source, and a…
Planet-forming disks are fundamental objects thought to be inherited from large scale rotation, through the conservation of angular momentum during the collapse of a prestellar dense core. We investigate the possibility for a protostellar disk to be formed from a motionless dense core which contains non-axisymmetric density fluctuations. The rotation is thus generated locally by the asymmetry of the collapse. We study the evolution of the angular momentum in a non-axisymmetric collapse of a dense core from an analytical point of view. To test the theory, we perform three-dimensional simulation…
We explore kinematics and morphologies of molecular outflows driven by young protostars using magnetohydrodynamic simulations in the context of the unified wind model of Shang et al. The model explains the observed high-velocity jet and low-velocity shell features. In this work we investigate how these characteristics are affected by the underlying temperature and magnetic field strength. We study the problem of a warm wind running into a cold ambient toroid by using a tracer field that keeps track of the wind material. While an isothermal equation of state is adopted, the effective temperatur…
