SiO J=5--4 in the HH211 Protostellar Jet Imaged with the SMA (original) (raw)

SiO J = 5-4 in the HH 211 Protostellar Jet Imaged with the Submillimeter Array

The Astrophysical Journal, 2006

We have mapped the SiO J=5-4 line at 217 GHz from the HH211 molecular outflow with the Submillimeter Array (SMA). The high resolution map (1.6 ′′ ×0.9 ′′ ) shows that the SiO J=5-4 emission comes from the central narrow jet along the outflow axis with a width of ∼0.8 ′′ (∼ 250 AU) FWHM. The SiO jet consists of a chain of knots separated by 3-4 ′′ (∼ 1000 AU) and most of the SiO knots have counterparts in shocked H 2 emission seen in a new, deep VLT near-infrared image of the outflow. A new, innermost pair of knots are discovered at just ±2 ′′ from the central star. The line ratio between the SiO J=5-4 data and upper limits from the SiO J=1-0 data of suggests that these knots have a temperature in excess of 300-500 K and a density of (0.5-1)×10 7 cm −3 . The radial velocity measured for these knots is ∼ 30 km s −1 , comparable to the maximum velocity seen in the entire jet. The high temperature, high density, and velocity structure observed in this pair of SiO knots suggest that they are closely related to the primary jet launched close to the protostar.

A highly-collimated SiO jet in the HH212 protostellar outflow

Astronomy and Astrophysics, 2007

′′ of the HH212 Class 0 outflow in SiO(2-1), SiO(5-4) and continuum using the Plateau de Bure interferometer in its extended configurations. The unprecedented angular resolution (down to 0. ′′ 34) allows accurate comparison with a new, deep H 2 image obtained at the VLT. The SiO emission is confined to a highly-collimated bipolar jet (width ∼ 0. ′′ 35) along the outflow axis. The jet can be traced down to within 500 AU of the protostar, in a region that is heavily obscured in H 2 images. Where both species are detected, SiO shows the same overall kinematics and structure as H 2 , indicating that both molecules are tracing the same material. We find that the high-velocity SiO gas is not tracing a wide-angle wind but is already confined to a flow inside a narrow cone of half-opening angle <6 • at ≤ 500 AU from the protostar. Transverse cuts reveal no velocity gradient compatible with jet rotation above 1 km s −1 , in contrast to previous claims based on H 2 spectra.

Subarcsecond Imaging of SiO in the HH 211 Protostellar Jet

The Astrophysical Journal, 2001

We present images of the HH 211 molecular jet in the SiO v=0, J=1-0 line at 43 GHz made with the Very Large Array at approximately 0.5 arcsec resolution. The SiO emission appears to trace primarily internal bowshocks in the outflow, suggesting that the dust and molecular gas are accelerated via prompt entrainment at internal working surfaces in the jet. There is also some evidence for limb-brightening of the SiO emission, indicating that SiO emission may also arise from entrainment in the jet's boundary layer. Excitation temperatures of 150-200 K are inferred from the SiO emission. Enhancements in the SiO abundance of ∼ 10 6 over interstellar values are observed, and the possible origin of the SiO is discussed.

HH 212: Submillimeter Array Observations of a Remarkable Protostellar Jet

The Astrophysical Journal, 2007

HH 212 is a nearby (460 pc) protostellar jet discovered in H 2 powered by a Class 0 source, IRAS 05413À0104. We have mapped it in 850 m continuum, SiO(J ¼ 8 7), CO(J ¼ 3 2), SO(N J ¼ 8 9 7 8 ), HCO + (J ¼ 4 3), and H 13 CO + (J ¼ 4 3) emission simultaneously at $1 00 resolution with the Submillimeter Array. Thermal dust emission is seen in continuum around the source, mainly arising from an inner envelope and a possible disk. The inner envelope is also seen with rotation in CO and HCO + , and probably in SO. Like H 2 emission, CO and SiO emission are seen along the jet axis but extending closer to the source, tracing the bow shocks and the continuous structures in between. SO emission is seen forming a jetlike structure extending from the source, likely tracing the jet near the launching region. The jet is episodic and bending. It may also be slightly precessing. A hint of jet rotation is also seen across the jet axis. Internal outflow shells are seen in CO and HCO + , associated with the bow shocks in the inner part of the jet. The bases of the HCO + shells are seen with a hint of rotation, probably consisting mainly of the material extending from the inner envelope and even the possible disk. The bases of the outflow shells are also seen in H 13 CO + and even the continuum, probably tracing the dense material extending from around the same regions.

HH 212: SMA Observations of a Remarkable Protostellar Jet

2007

HH 212 is a nearby (460 pc) protostellar jet discovered in H$_2$ powered by a Class 0 source, IRAS 05413-0104, in the L1630 cloud of Orion. It is highly collimated and symmetric with matched pairs of bow shocks on either side of the source. We have mapped it in 850 mu\mumum continuum, SiO ($J=8-7$), CO ($J=3-2$), SO ($N_J=8_9-7_8$), HCO$^+$ ($J = 4-3$), and H$^{13}$CO$^+$ ($J = 4-3$) emission simultaneously at sim\simsim 1$''$ resolution with the Submillimeter Array (SMA). Thermal dust emission is seen in continuum around the source, mainly arising from an inner envelope (i.e., the inner part of a previously seen flattened envelope) and a possible disk. The inner envelope is also seen with rotation in CO, HCO$^+$, and probably SO. Like H$_2$ emission, CO and SiO emission are seen along the jet axis but extending closer to the source, tracing the bow shocks with a broad range of velocities and the continuous structures in between. SO emission is seen only around the source, forming a jetlike structure extending along the jet axis from the source, likely tracing the jet near the launching region. The jet is episodic and bending. It may also be slightly precessing as the jetlike SO structure shows a slight S-shaped symmetry about the source. A hint of jet rotation is also seen across the jet axis. Internal outflow shells are seen in CO and HCO$^+$, associated with the bow shocks in the inner part of the jet. The bases of the HCO$^+$ shells are seen with a hint of rotation similar to that seen in the inner envelope, probably consisted mainly of the material extended from the inner envelope and even the possible disk.

Submillimeter Arcsecond‐Resolution Mapping of the Highly Collimated Protostellar Jet HH 211

The Astrophysical Journal, 2007

We have mapped the protostellar jet HH 211 in 342 GHz continuum, SiO (J = 8 − 7), and CO (J = 3 − 2) emission at ∼ 1 ′′ resolution with the Submillimeter Array (SMA). Thermal dust emission is seen in continuum at the center of the jet, tracing an envelope and a possible optically thick compact disk (with a size < 130 AU) around the protostar. A knotty jet is seen in CO and SiO as in H 2 , but extending closer to the protostar. It consists of a chain of knots on each side of the protostar, with an interknot spacing of ∼ 2 ′′ −3 ′′ or 600−900 AU and the innermost pair of knots at only ∼ 1 ′′ . 7 or 535 AU from the protostar. These knots likely trace unresolved internal (bow) shocks (i.e., working surfaces) in the jet, with a velocity range up to ∼ 25 km s −1 . The two-sided mass-loss rate of the jet is estimated to be ∼ (0.7 − 2.8) × 10 −6 M ⊙ yr −1 . The jet is episodic, precessing, and bending. A velocity gradient is seen consistently across two bright SiO knots (BK3 and RK2) perpendicular to the jet axis, with ∼ 1.5±0.8 km s −1 at ∼ 30±15 AU, suggesting a presence of a jet rotation. The launching radius of the jet, derived from the potential jet rotation, is ∼ 0.15−0.06 AU in the inner disk.

Observations of high-J SiO emission along the HH211 outflow

Astronomy and Astrophysics, 2002

Spectra of the pure rotational SiO J = 11-10 and J = 8-7 lines, at 477.5 GHz and 347.3 GHz respectively, have been obtained along the HH211 protostellar jet. Bright emission has been observed localized inside about 15 of projected distance from the central source, where a compact and collimated SiO jet was previously discovered by means of SiO J = 1-0 interferometric observations (Chandler & Richer 2001). The detection of the high-J lines testifies for the extreme conditions of density and temperature of the SiO emission. Values of T > 250 K and n H2 ∼ 2−5×10 6 cm −3 are inferred from the observed line ratios, while a SiO abundance in the range ∼10 −7 −10 −6 has been estimated through a comparison with the CO rotational lines at J > 14 observed by the ISO Long Wavelength Spectrometer. Both the estimated physical conditions and abundance are in agreement with a picture in which the observed SiO emission directly arises at the front of a C-type shock with v s < 35 km s −1 , where all the silicon released from the grains by sputtering and/or grain-grain collisions is converted into gas-phase SiO.

The excitation within the molecular hydrogen jets of the protostellar outflow HH 212

Astronomy and Astrophysics, 2007

The near-infrared twin jets emanating from the HH 212-mm protostar are remarkable for their symmetry. By performing integral field spectroscopy with the UIST imager-spectrometer on UKIRT, we investigate the chains of bright knots and arcs within the jets to gain insight into the underlying physics and dynamics. We obtain numerous images associated with line emission from vibrationally-excited molecular hydrogen and the [Fe II] line at 1.64 µm. This allows us to study the spatial variation in excitation of the inner knots and outer bow-shaped objects. We find that the excitation properties are consistent with outward-moving bow shocks close to the plane of the sky. However, there is a gradient in excitation transverse to the jet axis across the inner knots on the scale of 0.1 arcseconds. This C-shaped inner symmetry suggests a transverse source motion rather than precession, possibly related to the jet bending and the transverse gradient in radial velocity. Moreover, the bow models predict that the iron emission should peak further ahead of the molecular emission than actually observed. This leads us to propose that each inner knot consists of two closely-spaced asymmetric bows, as found for the outer bows which clearly occur in distinct pairs, well-separated in a lower density environment. The weak inter-knot emission may then be generated within oblique shock waves resulting from the deflection of fluid across asymmetric bow flanks.

Kinematics of SiOJ = 8-7 Emission towards the HH 212 Jet

Publications of the Astronomical Society of Japan, 2006

We present SiO J=8-7 (347.3 GHz) observations towards HH 212 using the ASTE telescope. Our observations with a 22"-diameter beam show that the SiO emission is highly concentrated within 1' of the driving source. We carefully compare the SiO observations with archival H 2 1-0 S(1) images and published H 2 echelle spectra. We find that, although the SiO velocities closely match the radial velocities seen in H 2 , the distribution of H 2 and SiO emission differ markedly. We attribute the latter to the different excitation conditions required for H 2 and SiO emission, particularly the higher critical density (n H2 ∼ 10 8 cm −3 ) of the SiO J=8-7 emission. The kinematic similarities imply that the H 2 and SiO are associated with the same internal working surfaces. We conclude that the SiO J=8-7 emission has a potential to probe the jet/wind launching region through interferometric observations in the future, particularly for the youngest, most deeply embedded protostars where IR observations are not possible.