arXiv subjects

Hsien Shang

Publications and source records attributed to Hsien Shang.

At least 19 recordsLinked to original sources

arXiv2026

Investigation of Calcium Dust in the Interstellar Medium

Calcium is a highly depleted element in the interstellar medium (ISM), however its composition in the solid phase remains elusive. The detection of Ca-bearing dust has been limited due to its lack of distinct spectral features in the cold phase of the diffuse ISM. X-rays provide a direct method for exploring the absorption and scattering properties of interstellar dust. In this study, we utilize high-resolution X-ray absorption spectroscopy to characterize Ca-bearing dust analogs at the Ca K-edge using X-ray Absorption Fine Structure (XAFS). We present new X-ray absorption spectra of seven calcium-bearing interstellar dust analogs measured at the National Synchrotron Radiation Research Center (NSRRC) in Taiwan. The extinction cross sections, calculated from the laboratory measurements are incorporated in the dust absorption model AMOL of the X-ray spectral fitting tool SPEX. We select three Low Mass X-ray Binaries (LMXBs) with high column densities, GX 340+00, GX 5-1, and GX 13+1, as background sources to study the intervening ISM along their sightlines. The best-fit models are compared with Chandra archive data using SPEX. Additionally, we employ simulations with the XRISM and NewAthena telescopes to achieve enhanced resolution and more effective coverage at the energy range near the Ca K-edge. These simulations set the boundary conditions for the future X-ray observation of calcium in the interstellar medium.

astro-ph.GA↗

arXiv2026

ALMA High-resolution Observation of the HH46/47 Outflow/disk/envelope System

We present $0.1^{\prime\prime}$ ($\sim 50$ au) resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations of the HH 46/47 molecular outflow and its envelope-disk system. The 1.3 mm continuum emission reveals a compact central source surrounded by a circumbinary disk with substructures. The companion, identified in optical and infrared observations, is not detected in the millimeter continuum but coincides with a local intensity minimum. Two spur-like features extending from the primary source toward the companion are identified and are likely induced by gravitational perturbations from the companion. The envelope-disk system is traced by C$^{18}$O, SO, H$_2$CO, and CH$_3$OH. C$^{18}$O primarily traces the extended envelope, while SO probes the inner envelope, and H$_2$CO and CH$_3$OH trace compact, faster-rotating structures near the centrifugal barrier. The observations are well reproduced by a rotating-infalling envelope transitioning to an inner disk at a radius of $\sim 30$ au around a $0.3~M_\odot$ protostar. The $^{12}$CO emission, together with JWST NIRCam images, reveals multiple shell structures in the outflow. Using C$^{18}$O and $^{13}$CO to correct for optical depth, we derive the spatial distributions of outflow mass, momentum, and kinetic energy, as well as their corresponding rates. A model-independent analysis of a well-defined redshifted shell yields its three-dimensional velocity field, showing that the shell expands radially rather than flowing along its surface. Although a transverse velocity gradient is detected, interpreting it as rotation implies an unphysically large magnetic lever arm, disfavoring a direct disk-wind origin. Instead, the shell kinematics support an entrainment scenario.

astro-ph.GA↗

arXiv2026

Iterative Poisson Solvers for Self-gravity with the GPU Code Astaroth

We present the development and benchmarking of Poisson solvers for graphics processing units (GPUs). Implemented in the Astaroth platform, the solvers feature high computational efficiency. We present novel combinations of discretizations and smoothers and document practical and performance-focused implementations aimed at reducing time-to-solution for self-gravitating systems. We describe the solver architectures and validate their accuracy against known analytic solutions. We measure convergence and timing per iteration for various solver algorithms, including conjugate gradient, successive overrelaxation, and multigrid in Cartesian coordinates, along with biconjugate gradient stabilized in spherical coordinates. We also couple the solvers to the Astaroth hydrodynamics to simulate a classic time-dependent problem in star formation, measuring accuracy and time-to-solution, for self-gravity on three-dimensional structured grids. Our results demonstrate that the solvers achieve performance similar to other algorithms implemented in Astaroth, and provide a solid foundation for integration into production-scale astrophysical simulations.

astro-ph.IM↗

arXiv2026

MAJORS II: HCO+& HCN Abundances in W40

We present observations of HCN and HCO$^+$ J = $3 - 2$ in the central $424'' \times 424''$ region of the W40 massive star forming region. The observations were taken as part of a pilot project for the MAJORS large program at the JCMT telescope. By incorporating prior knowledge of N(H$_2$) and $T_K$, assuming a constant density, and using the RADEX radiative transfer code we found that the HCN and HCO$^+$ abundances range from $X$(HCN) = $0.4-7.0 \times 10^{-8}$ and $X$(HCO$^+$) = $0.4-7.3 \times 10^{-9}$. Additional modelling using the NAUTILUS chemical evolution code, that takes H$_2$ density variations into account, however, suggests the HCN and HCO$^+$ abundances may be fairly constant. Careful modelling of three different positions finds $X$(HCN) = $1.3-1.7 \times 10^{-8}$, $X$(HCO$^+$) = $1.3-3.1 \times 10^{-9}$. Cross-comparison of the two models also provides a crude estimate of the gas density producing the HCN and HCO$^+$ emission, with H$_2$ densities in the range $5 \times 10^4 - 5 \times 10^5$ cm$^{-3}$, suggesting that the HCN and HCO$^+$ emission does indeed arise from dense gas. High UV intensity (e.g. $G_o >$ a few thousand) has no effect on the abundances in regions where the visual extinction is large enough to effectively shield the gas from the UV field. In regions where $A_V < 6$, however, the abundance of both species is lowered due to destructive reactions with species that are directly affected by the radiation field.

astro-ph.GA↗

arXiv2026

HOPS-288: A Laboratory for Complex Organics in Proto-multiple Systems

Complex organic molecules (COMs) in young stellar objects (YSOs) have attracted significant attention in recent years due to their potential connection to pre-biotic chemistry and their utility as tracers of warm or shocked gas components. Proto-binary and multiple systems with close separations are particularly valuable targets for investigating chemical inheritance and reaction, as their members are expected to form from similar material in their parental cloud. We present ALMA observations of the hierarchical proto-triple system HOPS-288, focusing on the physical structure, kinematics, and COM compositions. The system is treated as a proto-binary system consisting of HOPS-288-A and HOPS-288-B due to the limited spatial resolutions, with a separation of 200~au. Three COM-rich features are revealed: two hot corinos associated with the two members, rich in a variety of COMs, and an intervening component between the two members traced by CH$_3$OH and tentatively by CH$_3$CHO. The hot corino in HOPS-288-A exhibits rotational features and might trace a disk. The hot corino in HOPS-288-B is also possibly exhibiting rotational motion. The intervening component could possibly trace a shocked region in the circumbinary disk or a bridge between the two members. The column densities of COMs, including $^{13}$CH$_3$OH, CH$_2$DOH, CH$_3$CHO, HCOOCH$_3$, C$_2$H$_5$OH, $^{13}$CH$_3$CN, and NH$_2$CHO, are broadly similar between the two sources, possibly suggesting the complex organic similarities among proto-binary/multiple systems. Given the complexity of the studied physical structures, further detailed investigations will be essential to confirm this result.

astro-ph.SR↗

arXiv2025

Early Planet Formation in Embedded Disks (eDisk). XIX. Structures of molecular outflows

As part of the ALMA Large Program "Early Planet Formation in Embedded Disks" (eDisk), 12CO (2 - 1) was observed towards 19 nearby low-mass protostars. Of these objects, 15 sources are found to show molecular outflow emission. Based on their morphological and kinematical structures, the CO outflows are classified into three types: a wind-driven shell, where ambient material is swept up by a wide-angle wind from the star, a bow shock, and a slow disk wind, which is a conical or parabolic flow with onion-like velocity structure. We categorize 11 outflows as a slow disk wind, 7 as a wind-driven shell, and 1 as a bow shock. Four of these outflows were found to show signs of both slow disk wind and wind-driven shell characteristics. Five objects show misalignment between the red- and blue-shifted outflows. Seven objects show significant misalignment between the outflow axis (either or both of the red- and blue-shifted outflows) and the minor axis of the dust continuum emission around the protostar. For the objects showing wind-driven shell emission, we compare simple parametrized models with the observations to derive physical properties of the observed shells, such as their dynamical ages. This shows evidence of a time variability in the outflows, such as changes in their direction. In some objects, large differences are seen between the properties of the red- and blue-shifted outflows, possibly indicating differences in the properties of the ambient medium with which the outflow interacts.

astro-ph.SR↗

arXiv2025

Constraining Active Galactic Nucleus Jets with Spectrum and Core Shift: The Case of M87

We analytically model stationary and axisymmetric active galactic nucleus jets, assuming energy conservation along each magnetic flux tube. Using very-long-baseline interferometry (VLBI) observations and published general relativistic magnetohydrodynamic simulations, we constrain the evolution of the bulk Lorentz factor, the magnetization parameter, and the magnetic field strength along the jet. We then infer the electron density, emission coefficient, and absorption coefficient at each point, and integrate the radiative transfer equation to compute the spectral energy distribution (SED) and the core shift of the synchrotron emission from the relativistic jet. Applying the method to the M87 jet, we find that the hot plasmas are injected at the altitude of seven Schwarzschild radii from the black hole (BH), that the M87 jet is likely composed of a pair plasma, and that the jet flowline geometry is quasi-parabolic as reported at much greater distances. Fitting the nonthermal fraction of the leptonic jet as a function of position, we also find that most of the radio photons are emitted within 1000 Schwarzschild radii from the BH. Although hadronic jets do not reproduce all the VLBI observations consistently in our model, we also discuss that their heavy mass allows a stronger magnetic field within the observational constraints, leading to an inverted SED in sub-millimeter wavelengths by the thermal emission from the jet base. It is therefore implied that contemporaneous observations of the M87 jet with Atacama Large Millimeter/submillimeter Array (ALMA) and VLBI could discriminate the jet composition and its collimation within the central 100 Schwarzschild radii.

astro-ph.HE↗

arXiv2025

ALMASOP. A Rotating Feature Rich in Complex Organic Molecules in a Protostellar Core

Interstellar complex organic molecules (COMs) in solar-like young stellar objects (YSOs), particularly within protostellar disks, are of significant interest due to their potential connection to prebiotic chemistry in emerging planetary systems. We report the discovery of a rotating feature enriched in COMs, including CH3OH, CH3CHO, and NH2CHO, in the protostellar core G192.12-11.10. By constructing a YSO model, we find that the COM-rich feature is likely located within or near the boundary of the Keplerian disk. The image synthesis results suggest that additional heating mechanisms leading to a warm ring or a warm inner disk are required to reproduce the observed emission. We discuss possible origins of the COM-rich feature, particularly accretion shocks as a plausible cause for a warm ring. Additionally, molecules such as C18O, H2CO, DCS, H2S, and OCS exhibit distinct behavior compared to CH3OH, indicating a range of physical and chemical conditions within the region. The observed kinematics of H2S and OCS suggest that OCS resides in regions closer to the central protostar than H2S, consistent with previous experimental studies.

astro-ph.GA↗

arXiv2025

Polytropic Wind-Driven Bubbles and their Shock Structures in Radially Stratified Ambient Media

We extend the analytic expressions for polytropic wind-driven bubbles and their shock structures, formulated initially in Koo and McKee 1992(a,b), focusing on spherically symmetric configurations in astrophysical environments with $\rho\propto r^{-2}$, which arises naturally in the star-forming environment and has applications to winds flowing into a preexisting bubble. Wind luminosity is assumed to be constant, and as a result the shock velocities of these bubbles are constant in time. The ratio of specific heats is assumed to be the same in the shocked ambient medium and the shocked wind. Numerical results are presented for one selected ratio of wind density to ambient density. Exact ODEs are written for the compressed wind region and approximate solutions are found by fitting the ODE solutions. By analyzing the interactions between stellar winds and ambient media in the strong compression limit, we model the formation and evolution of spherical bubbles, highlighting their shock fronts and contact discontinuities. Our analytic method provides an intuitive approach to calculating the thickness of bubble shells, which is crucial for understanding their dynamics and observational characteristics. A numerical method explores conditions without explicitly requiring the strong compression limit, and then we compare numerical to analytical results under various conditions.

astro-ph.HE↗

arXiv2025

Nonlinear Stability and Dynamics of Supersonic Compressible Flows

The study of shear layer instability in compressible flows is key to understanding phenomena from aerodynamics to astrophysical jets. Blumen's seminal paper [``Shear layer instability of an inviscid compressible fluid," J. Fluid Mech. {\bf 40}, 769--781 (1970)] established a linear stability framework for inviscid compressible shear flows, emphasizing velocity gradients and compressibility effects. However, the nonlinear regime remains insufficiently explored. This research extends Blumen's framework by conducting a weakly nonlinear stability analysis using the method of multiple scales to derive amplitude equations, such as the Landau-Stuart and complex Landau equations. Perturbation variables are expanded in a power series to capture amplitude evolution beyond linear theory. Finite boundary conditions are incorporated to enhance physical applicability. The study analyzes how compressibility and Mach number influence nonlinear saturation, revealing Mach-dependent bifurcations in Kelvin-Helmholtz instability (KHI) with alternating stable and unstable regimes. Phase portraits and trajectories illustrate transitions, saturation, and spiral decay, which are relevant to astrophysical shear flows. Bifurcation analysis reveals both supercritical and subcritical Hopf behavior in compressible shear flows, underscoring the importance of nonlinear effects in the onset and evolution of flow instabilities. Qualitative and quantitative results of instability evolution have been shown from nonlinear stability analysis. This work bridges the critical gap between linear and fully nonlinear stability analyses by offering a systematic weakly nonlinear framework and the nonlinear dynamics for compressible shear layers. It generalizes the earlier linear results and provides new predictions about bifurcation behavior and long-time state selection in compressible flows.

physics.flu-dyn↗

arXiv2025

Resistive Collapse of 2D Non-rotating Magnetized Isothermal Toroids: Formation of Pseudodisks

The collapse of singular magnetized toroids (Li & Shu 1996) is a natural representation of an early phase in star formation, bridging the prestellar and protostellar phases of the collapse of molecular cloud cores. We revisit the collapse study of Allen et al. (2003b), now with explicit nonideal MHD (Ohmic diffusivity $\eta$) and higher resolution using a code able to cover a broader range of the magnetization parameter $H_0$. Galli-Shu equatorial pseudodisks form for all values of $H_0$ and $\eta$, and the asymptotic central mass growth rate is in the scale $\dot{M}_*\sim(a^3/G)(1+H_0)$, where $a$ is the isothermal sound speed, consistent with previous results and predictions. The explicit Ohmic diffusivity makes the field line structure less radial than in previous work, connecting the pseudodisk more effectively to its surroundings. Matter can fall efficiently onto the pseudodisk surfaces, forming oblique shocks, where shock heating and large density gradients raise the possibility of rich astrochemistry. Pseudodisk size and structure are influenced by magnetic diffusivity. Force and velocity ratios were computed to explore the magnetic support within the pseudodisk and its induced slowdown in infall velocity. Magnetic diffusivity was measured to control the strength of these effects and their location within the pseudodisk. The dependence of the field line configurations, pseudodisk structure, and velocity ratios on magnetic diffusivity has observable consequences for collapsing envelopes.

astro-ph.SR↗

arXiv2025

R-JET: A postprocessing code for radiative transport in relativistic jets

We describe a post-processing radiative transport code for computing the spectra, the coreshift, and the surface-brightness distribution of special relativistic jets with arbitrary optical thickness. The jet consists of an electron-positron pair plasma and an electron-proton normal plasma. Electrons and positrons are relativistic and composed of thermal and nonthermal components, while protons are non-relativistic and non-radiating. The fraction of a pair plasma, as well as the fraction of a nonthermal component can be arbitrarily chosen. Only the synchrotron process is considered for emission and absorption when the radiative-transfer equation is integrated along our lines of sight. We describe a suite of test problems, and confirm the frequency dependence of the coreshift in the Konigl jet model, when the plasma is composed of nonthermal component alone. Finally, we illustrate the capabilities of the code with model calculations, demonstrating that the jet will exhibit a limb-brightened structure in general when it is energized by the rotational energy of the black hole. It is also demonstrated that such limb-brightened jets show a ring-like structure in the brightness map when we observe the jet launching region nearly face-on.

astro-ph.HE↗

arXiv2025

A Spectroastrometric Study of the Low-velocity Wind from DG Tau A

We obtained high spectral resolution spectra ($\Delta v$ $\sim$ 2.5 km s$^{-1}$) for DG Tau A from 4800 \r{A} to 7500 \r{A} using Subaru High Dispersion Spectrograph (HDS) for the first time. The low-velocity components (LVCs, |$v$| < 100 km s$^{-1}$) were observed in the [O I] 5577, 6300, 6364 \r{A}, [S II] 6716, 6731 \r{A} lines. The offset position spectra observed in the LVCs show a "negative velocity gradient", supporting the presence of a wide-angled wind associated with the LVC emission. The offset position spectra observed in a component within the LVC velocity range between -16 km s$^{-1}$ to -41 km s$^{-1}$, namely, LVC-M, show a "negative velocity gradient'', supporting the presence of a wide-angled wind. With 12-70 au wind lengths measured using spectroastrometry, we estimate a lower limit to the wind mass-loss rate of $\sim$10$^{-8}$ M$_\odot$ yr$^{-1}$. In addition to the LVCs, we identify two high-velocity components (HVCs, |$v$| > 100 km s$^{-1}$) associated with the collimated jet in 26 lines ([N I], [N II], [O I], [O II], [O III], [S II], [Ca II], [Fe II], H$\alpha$, H$\beta$, He I). The one with a clear spatial offset from the star ($n_e$ $\sim$10$^4$ cm$^{-3}$, HVC1) is associated with an internal shock surface of the jet, while the other at the base ($n_e$ $\sim$10$^6$ cm$^{-3}$, HVC2) may be a stationary shock component. We find that the observed line profiles and the spatial scales of the LVC emission do not agree with the existing predictions for photoevaporative or magnetohydrodynamical (MHD) disk winds. These could be explained by the X-wind model, but synthetic observations are required for detailed comparisons.

astro-ph.SR↗

arXiv2025

How Does a Protostar Form by Magnetized Gravitational Collapse?

Star formation through the dynamical magnetized collapse remains an active area of astrophysical research. We carry out a comprehensive exploration on the magnetized gravitational collapse of a non-rotating self-gravitating initially spherically symmetric prestellar cloud core using two-dimensional nonideal magnetohydrodynamic simulations incorporating ambipolar diffusion and Ohmic dissipation. Our study encompasses a broader range of equations of state (EOSs) in the form of $P(\rho) \propto \rho^{\Gamma}$, with the aim of constraining the choice of EOSs for allowing star formation. Our results reveal that the collapse with a $\Gamma$ no stiffer than $4/3$, complemented by magnetized virial theorem, allows the dynamical contraction of the prestellar core to happen continuously where a central point mass forms and steadily builds up its mass from the infalling envelope, with a mass accretion rate of a scale of the order of $c_{\rm s}^3/G$. The choice of an isothermal EOS most naturally facilitates the collapse as a magnetic analog of the inside-out collapse. In addition to that, our study exhibits that the nonisothermal magnetized collapse models with a $\Gamma$ no stiffer than 4/3 qualitatively demonstrate similar infall features to those of an isothermal EOS. Furthermore, the collapse models with a $\Gamma$ stiffer than $4/3$ fail to ensure the sufficient cooling to allow the direct mass growth of the central point mass, thus delaying the infall. Our work can offer deeper insights in understanding the significance of EOSs on the magnetized gravitational collapse, enabling star formation.

astro-ph.GA↗

arXiv2025

Evidence of a Disk-wind Origin for Fluorescent H$_2$ in Classical T Tauri Stars

We use FUV spectra of 36 T Tauri stars, predominately from $\textit{Hubble Space Telescope}$'s ULLYSES program, to examine the kinematic properties of fluorescent H$_2$ emission lines for evidence of disk outflows. Leveraging improvements to the $\textit{HST}$-COS wavelength solution, we co-add isolated lines within four fluorescent progressions ([$\textit{v'}$,$\textit{J'}$] = [1,4], [1,7], [0,2], and [3,16]) to improve signal-to-noise, and we fit each co-added line profile with one or two Gaussian components. Of the high S/N line profiles (S/N $\geq$ 12 at the peak of the profile), over half are best fit with a combination of a broad and narrow Gaussian component. For profiles of the [1,4] and [1,7] progressions, we find a systematic blue-shift of a few km s$^{-1}$ between the broad and narrow centroid velocities and stellar radial velocities. For the [0,2] progression, we find centroid velocities consistently blueshifted with respect to stellar radial velocities on the order of -5 km s$^{-1}$ for the single and narrow components, and -10 km s$^{-1}$ for the broad components. Overall, the blueshifts observed in our sample suggest that the molecular gas traces an outflow from a disk wind in some sources, and not solely disk gas in Keplerian rotation. The low-velocity systematic blue-shifts, and emitting radii as inferred from line FWHMs, observed in our sample are similar to those observed with optical [O I] surveys of T Tauri stars. We estimate H$_2$ mass-loss rates of 10$^{-9}$ to 10$^{-11}$ $M_{\odot}$ yr$^{-1}$, but incomplete knowledge of wind parameters limits comparisons to global models.

astro-ph.SR↗

arXiv2024

ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP): Nested Morphological and Kinematic Structures of Outflows Revealed in SiO and CO Emission

The Atacama Large Millimeter/submillimeter Array Survey of Orion Planck Galactic Cold Clumps (ALMASOP) reveals complex nested morphological and kinematic features of molecular outflows through the CO (J = 2 - 1) and SiO (J = 5 - 4) emission. We characterize the jet and outflow kinematics of the ALMASOP sample in four representative sources (HOPS 10, 315, 358, and G203.21-11.20W2) through channel maps and position-velocity diagrams (PVDs) parallel and transverse to the outflow axes. The combined CO and SiO emission exhibits the coexistence of the conventional extremely-high-velocity (EHV) jets and shell-like low-velocity (LV) cavity walls and new features. More complex, nested bubble-like and filamentary structures in the images and channel maps, triangle-shaped regions near the base of the parallel PVDs, and regions composed of rhombus/oval shapes in the transverse PVDs, are also evident. Such features find natural explanations within the bubble structure of the unified model of jet, wind, and ambient medium. The reverse shock cavity is revealed on the PVD base regions, and other features naturally arise within the dynamic postshock region of magnetic interaction. The finer nested shells observed within the compressed wind region reveal previously unnoticed shocked emission between the jet and the conventional large cavity walls. These pseudopulse-produced filamentary features connect to the jet-like knotty blobs, creating an impression of episodicity in mass ejection. SiO emission is enhanced downstream of the reverse shock boundary, with jet-like excitation conditions. Combined, these observed features reveal the extended structures induced by the magnetic interplay between a jet-bearing magnetized wide-angle wind and its ambient magnetized surrounding medium.

astro-ph.SR↗

arXiv2024

Chemical Fingerprints of M Dwarfs: High-Resolution Spectroscopy on 31 M Dwarfs with SPIRou

We extend the methodology introduced by Jahandar et al. (2024) to determine the effective temperature and chemical abundances of 31 slowly-rotating solar neighborhood M dwarfs (M1-M5) using high-resolution spectra from CFHT/SPIRou. This group includes 10 M dwarfs in binary systems with FGK primaries of known metallicity from optical measurements. By testing our $T_{\rm eff}$ method on various synthetic models, we find a consistent inherent synthetic uncertainty of $\sim$10 K at a signal-to-noise ratio greater than 100. Additionally, we find that our results align with interferometric measurements, showing a consistent residual of $-$29 $\pm$ 31 K. Taking the inherent uncertainties into account, we infer the $T_{\rm eff}$ values of our targets and find an excellent agreement with previous optical and NIR studies. Our high-resolution chemical analysis examines hundreds of absorption lines using $\chi^2$ minimization using PHOENIX-ACES stellar atmosphere models. We present elemental abundances for up to 10 different elements, including refractory elements such as Si, Mg, and Fe, which are important for modelling the interior structure of exoplanets. In binary systems, we find an average [Fe/H] of $-$0.15 $\pm$ 0.08 for M dwarfs, marginally lower than the reported metallicity of $-$0.06 $\pm$ 0.18 for the FGK primaries from Mann et al. (2013a). We also observe slightly sub-solar chemistry for various elements in our non-binary M dwarfs, most notably for O, C, and K abundances. In particular, we find an average metallicity of $-$0.11 $\pm$ 0.16 lower but still consistent with the typical solar metallicity of FGK stars (e.g. [Fe/H] = 0.04 $\pm$ 0.20 from Brewer et al. 2016). This study highlights significant discrepancies in various major M dwarf surveys likely related to differences in the methodologies employed.

astro-ph.SR↗

arXiv2024

Multiple Components of the Outflow in the Protostellar System HH 212: Outer Outflow Shell, Rotating Wind, Shocked Wind, and Jet

We present the Atacama Large Millimeter/submillimeter Array Band 7 observations of the CO (J=3-2) line emission of the protostellar system HH 212 at $\sim$24 au spatial resolution and compare them to those of the SiO (J=8-7) and SO (J=8-7) line emission reported in the literature. We find that the CO line traces four distinct regions: (1) an outer outflow shell, (2) a rotating wind region between the SiO and CO shells, (3) the shocked and wide-angle inner X-wind inside a SiO shell, and (4) the jet. The origin of the CO outer outflow shell could be associated with the entrained material of the envelope, or an extended disk wind. The rotating wind, which is shocked, is launched from a radius of 9-15 au, slightly exterior to that of the previously detected SO shell, which marks the boundary where the wide-angle X-wind is interacting with and shocking the disk wind. Additionally, the SO is found to be mixed with the CO emission within the thick and extended rotating wind region. The large scale CO shocked wind coexists with the SO emission near the upper portion of the inner shocked region converged on top of the inner SiO knots. The CO jet is traced by a chain of knots with roughly equal interval, exhibiting quasi-periodicity, as reported in other jets in the literature.

astro-ph.SR↗