The flattened, rotating molecular gas core of protostellar jet HH 212 (original) (raw)
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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.
H 2 active jets in the near IR as a probe of protostellar evolution
Astronomy and Astrophysics, 2006
We present an in-depth near-IR analysis of a sample of H2 outflows from young embedded sources to compare the physical properties and cooling mechanisms of the different flows. The sample comprises 23 outflows driven by Class 0 and I sources having low-intermediate luminosity. We have obtained narrow band images in H2 2.12 µm and [Fe ii] 1.64 µm and spectroscopic observations in the range 1-2.5 µm. From [Fe ii] images we detected spots of ionized gas in ∼74% of the outflows which in some cases indicate the presence of embedded HH-like objects. H2 line ratios have been used to estimate the visual extinction and average temperature of the molecular gas. Av values range from ∼2 to ∼15 mag; average temperatures range between ∼2000 and ∼4000 K. In several knots, however, a stratification of temperatures is found with maximum values up to 5000 K. Such a stratification is more commonly observed in those knots which also show [Fe ii] emission, while a thermalized gas at a single temperature is generally found in knots emitting only in molecular lines. Combining narrow band imaging (H2, 2.12 µm and [Fe ii], 1.64 µm) with the parameters derived from the spectroscopic analysis, we are able to measure the total luminosity of the H2 and [Fe ii] shocked regions (LH 2 and L [Fe ii]) in each flow. H2 is the major NIR coolant with an average LH 2 /L [Fe ii] ratio of ∼10 2. We find that ∼83% of the sources have a LH 2 /L bol ratio ∼0.04, irrespective of the Class of the driving source, while a smaller group of sources (mostly Class I) have LH 2 /L bol an order of magnitude smaller. Such a separation reveals the non-homogeneous behaviour of Class I, where sources with very different outflow activity can be found. This is consistent with other studies showing that among Class I one can find objects with different accretion properties, and it demonstrates that the H2 power in the jet can be a powerful tool to identify the most active sources among the objects of this class.
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.
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.
JET MOTION, INTERNAL WORKING SURFACES, AND NESTED SHELLS IN THE PROTOSTELLAR SYSTEM HH 212
The Astrophysical Journal, 2015
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 (SMA) at unprecedented sensitivity. The jet consists of a chain of knots andbow shocks withsinuous structures in between. Compared to what we sawin our previous observations with the SMA, the jetappears to be more continuous, especially in the northern part. Some of the knots are now observed to be associated with small bow shocks, with their bow wings curving back to the jet axis, as seen in pulsed jet simulations. Two of the knots 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 −1 , comparing with our previous observations.The jet has a small semi-periodical wigglewith a period of ∼93 yr. 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.
A jet-like outflow toward the high-mass (proto) stellar object IRAS 18566+0408
Astronomy and Astrophysics, 2007
Context. Studies of high-mass protostellar objects reveal important information regarding the formation process of massive stars. Aims. We study the physical conditions in the dense core and molecular outflow associated with the high-mass protostellar candidate IRAS 18566+0408 at high angular resolution. Methods. We performed interferometric observations in the NH 3 (J, K) = (1, 1), (2, 2) and (3,3) inversion transitions, the SiO J = 2-1 and HCN J = 1-0 lines, and the 43 and 87 GHz continuum emission using the VLA and OVRO. Results. The 87 GHz continuum emission reveals two continuum peaks MM-1 and MM-2 along a molecular ridge. The dominant peak MM-1 coincides with a compact emission feature at 43 GHz, and arises mostly from the dust emission. For dust emissivity index β of 1.3, the masses in the dust peaks amount to 70 M for MM-1, and 27 M for MM-2. Assuming internal heating, the central luminosities of MM-1 and MM-2 are 6 × 10 4 and 8 × 10 3 L , respectively. The SiO emission reveals a well collimated outflow emanating from MM-1. The jet-like outflow is also detected in NH 3 at velocities similar to the SiO emission. The outflow, with a mass of 27 M , causes significant heating in the gas to temperatures of 70 K, much higher than the temperature of < ∼ 15 K in the extended core. Compact (<3 ) and narrow line (<1.5 km s −1 ) NH 3 (3,3) emission features are found associated with the outflow. They likely arise from weak population inversion in NH 3 similar to the maser emission. Toward MM-1, there is a compact NH 3 structure with a linewidth that increases from 5.5 km s −1 FWHM measured at 3 resolution to 8.7 km s −1 measured at 1 resolution. This linewidth is much larger than the FWHM of <2 km s −1 in the entire core, and does not appear to originate from the outflow. This large linewidth may arise from rotation/infall, or relative motions of unresolved protostellar cores.
This paper is one of a series in which we report on near infrared imaging of outflow complexes in the H2 v=I-0 S(I) (2.l2Jlm) emission line. Here we discuss observations of HHI and HH2, HH34, HH46 and HH47, HHII0, HHlll and HH144, which are associated with well collimated jets. We observe molecular hydrogen emission associated with regions within the highly collimated, blue-shifted jets ofHHl, HH46 and HHlll. This low excitation emission is most simply explained in terms of bow shocks within a periodic outflow. Molecular emission is also found associated with the Mach disks HH47D and HH46C implying the existence of H2 molecules within the HH46/HH47 flow. The edges of the red-shifted outflow cavity of HH46 and HH47 are clearly outlined by molecular hydrogen emission. This extends from the working surface back towards the reflection nebulosity close to the source. This emission may result from entrainment of ambient material at the flow edges or from material within the flow being obl...
The Astrophysical Journal, 1997
We present new narrow-band near-infrared images together with K band spectra of highly collimated bipolar jets close to the IRAS 05487+0255 source. The jets are located at ∼ 50 ′′ West of the Herbig-Haro 110 outflow. The jets are not visible at optical wavelengths, and therefore, do not fall into the 'standard' Herbig-Haro object classification scheme. Nevertheless, they belong to an ever growing group of molecular hydrogen jets associated with YSOs which are optically undetected.
Molecular jets driven by high-mass protostars: a detailed study of the IRAS 20126+4104 jet
Astronomy and Astrophysics, 2008
Context. Protostellar jets from intermediate-and high-mass protostars provide an excellent opportunity to understand the mechanisms responsible for intermediate-and high-mass star formation. A crucial question is if they are scaled-up versions of their low-mass counterparts. Such high-mass jets are relatively rare and, usually, they are distant and highly embedded in their parental clouds. The IRAS 20126+4104 molecular jet, driven by a 10 4 L ⊙ protostar, represents a suitable target to investigate. Aims. We present here an extensive analysis of this protostellar jet, deriving the kinematical, dynamical, and physical conditions of the H 2 gas along the flow. Methods. The jet has been investigated by means of near-IR H 2 and [Fe ii] narrow-band imaging, high resolution spectroscopy of the 1-0 S(1) line (2.12 µm), NIR (0.9-2.5 µm) low resolution spectroscopy, along with ISO-SWS and LWS spectra (from 2.4 to 200 µm). Results. The flow shows a complex morphology. In addition to the large-scale jet precession presented in previous studies, we detect a small-scale wiggling close to the source, that may indicate the presence of a multiple system. The peak radial velocities of the H 2 knots range from-42 to-14 km s −1 in the blue lobe, and from-8 to 47 km s −1 in the red lobe. The low resolution spectra are rich in H 2 emission, and relatively faint [Fe ii] (NIR), [O i] and [C ii] (FIR) emission is observed in the region close to the source. A warm H 2 gas component has an average excitation temperature that ranges between 2000 K and 2500 K. Additionally, the ISO-SWS spectrum reveals the presence of a cold component (520 K), that strongly contributes to the radiative cooling of the flow and plays a major role in the dynamics of the flow. The estimated L H 2 of the jet is 8.2±0.7 L ⊙ , suggesting that IRAS 20126+4104 has an accretion rate significantly increased compared to low-mass YSOs. This is also supported by the derived mass flux rate from the H 2 lines (Ṁ out (H 2)∼7.5×10 −4 M ⊙ yr −1). The comparison between the H 2 and the outflow parameters strongly indicates that the jet is driving, at least partially, the outflow. As already found for low-mass protostellar jets, the measured H 2 outflow luminosity is tightly related to the source bolometric luminosity. Conclusions. As for few other intermediate-and high-mass protostellar jets in the literature, we conclude that IRAS 20126+4104 jet is a scaled-up version of low-mass protostellar counterparts.