Anatomy of HH 111 from CO Observations: A Bow‐Shock‐driven Molecular Outflow (original) (raw)

THE CHESS SURVEY OF THE L1157-B1 SHOCK REGION: CO SPECTRAL SIGNATURES OF JET-DRIVEN BOW SHOCKS

The Astrophysical Journal, 2012

The unprecedented sensitivity of Herschel coupled with the high resolution of the HIFI spectrometer permits studies of the intensity-velocity relationship I(v) in molecular outflows, over a higher excitation range than possible up to now. Over the course of the CHESS Key Program, we have observed toward the bright bow shock region L1157-B1, the CO rotational transitions between J = 5-4 and J = 16-15 with HIFI, and the J = 1-0, 2-1, and 3-2 with the IRAM 30 m and the Caltech Submillimeter Observatory telescopes. We find that all the line profiles I CO (v) are well fit by a linear combination of three exponential laws ∝ exp(−|v/v 0 |) with v 0 = 12.5, 4.4, and 2.5kms −1 . The first component dominates the CO emission at J 13, as well as the high-excitation lines of SiO and H 2 O. The second component dominates for 3 J up 10 and the third one for J up 2. We show that these exponentials are the signature of quasi-isothermal shocked gas components: the impact of the jet against the L1157-B1 bow shock (T k ≃ 210 K), the walls of the outflow cavity associated with B1 (T k ≃ 64 K), and the older cavity L1157-B2 (T k ≃ 23 K), respectively. Analysis of the CO line flux in the large-velocity gradient approximation further shows that the emission arises from dense gas (n 10 5 -10 6 cm −3 ) close to LTE up to J = 20. We find that the CO J = 2-1 intensity-velocity relation observed in various other molecular outflows is satisfactorily fit by similar exponential laws, which may hold an important clue to their entrainment process.

A near-infrared study of the bow shocks within the L1634 protostellar outflow

Astronomy and Astrophysics, 2004

The L1634 bright-rimmed globule contains an intriguing arrangement of shock structures: two series of aligned molecular shock waves associated with the Herbig-Haro flows HH 240 and HH 241. We present near-infrared spectroscopy and narrow-band imaging in the (1, 0) S(1) and (2, 1) S(1) emission lines of molecular hydrogen. These observations yield the spatial distributions of both the molecular excitation and velocity, which demonstrate distinct properties for the individual bow shocks. Bow shock models are applied, varying the shock physics, geometry, speed, density and magnetic field properties to fit two prominent bow shocks. The models predict that both bows move at 60 • to the plane of the sky. High magnetic fields and low molecular fractions are implied. The advancing compact bow HH 240C is interpreted as a J-type bow (frozen-in magnetic field) with the flanks in transition to C-type (field diffusion). It is a paraboloidal bow of speed ∼42 km s −1 entering a medium of quite high density (2 × 10 4 cm −3 ). The following bow HH 240A is faster despite a lower excitation, moving through a lower density medium. We find a C-type bow shock model to fit all the data for HH 240A. The favoured bow models are then tested comprehensively against published H 2 emission line fluxes and CO spectroscopy. We conclude that, while the CO emission originates from cloud gas directly set in motion, the H 2 emission is generated from shocks sweeping through an outflow. Also considering optical data, we arrive at a global outflow model involving episodic slow-precessing twin jets.

Herbig-Haro Jets, CO Flows, and CO Bullets: The Case of HH 111

The Astrophysical Journal, 1996

We have carried out high spatial resolution, 12Љ, CO J ϭ 2-1 observations at the IRAM 30 m telescope of the molecular outflow in the HH 111 jet complex. The Herbig-Haro jet is found to coincide with a highly collimated CO flow, with two distinct velocities, possibly providing kinematic evidence that the CO flow surrounds the HH jet. A second well-defined bipolar molecular flow, at large angles to the principal flow axis, coincides with the HH 121 infrared flow that emanates from the (presumably binary) VLA driving source; the region thus harbors one of the rare quadrupolar molecular flows. Extremely high velocity CO is found toward the principal HH working surface at the same velocity as the optically emitting gas, whereas this emission is weak toward the Herbig-Haro jet. Since the inclination of the HH jet is known from optical observations to be 10Њ to the plane of the sky, we conclude that there is CO in the flow with space velocities of up to 500 km s Ϫ1 ! Further out, and precisely along the flow axis, we have discovered three equidistant CO bullets with space velocities of about 240 km s Ϫ1 , which are not detected in the optical. We interpret these bullets as the result of earlier eruptions from the energy source that are now moving through an ambient medium so tenuous that no observable shock interaction takes place. Finally, we discuss the physical relation between the Herbig-Haro jet, the CO bullets, and the low-velocity molecular outflow. We favor the view that HH jets and CO bullets, which represent different manifestations of the same physical phenomena, are driving the low-velocity molecular outflow.

Submillimeter Emission from the Hot Molecular Jet HH 211

The Astrophysical Journal, 2006

We observed the HH 211 jet in the submillimeter continuum and the CO(3-2) and SiO(8-7) transitions with the Submillimeter Array. The continuum source detected at the center of the outflow shows an elongated morphology, perpendicular to the direction of the outflow axis. The high-velocity emission of both molecules shows a knotty and highly collimated structure. The SiO(8-7) emission at the base of the outflow, close to the driving source, spans a wide range of velocities, from −20 up to 40 km s −1 . This suggests that a wide-angle wind may be the driving mechanism of the HH 211 outflow. For distances ≥ 5 ′′ (∼ 1500 AU) from the driving source, emission from both transitions follows a Hubble-law behavior, with SiO(8-7) reaching higher velocities than CO(3-2), and being located upstream of the CO(3-2) knots. This indicates that the SiO(8-7) emission is likely tracing entrained gas very close to the primary jet, while the CO(3-2) is tracing less dense entrained gas. From the SiO(5-4) data of Hirano et al. we find that the SiO(8-7)/SiO(5-4) brightness temperature ratio along the jet decreases for knots far from the driving source. This is consistent with the density decreasing along the jet, from (3-10)×10 6 cm −3 at 500 AU to (0.8-4)×10 6 cm −3 at 5000 AU from the driving source.

Observations of Shocked H[TINF]2[/TINF] and Entrained CO in Outflows from Luminous Young Stars

The Astronomical Journal, 1998

Narrowband, (1È0) S(1) images of six luminous outÑow regions are presented and discussed. In Ðve H 2 of these regions, W75 N, S140 N, NGC 7538, AFGL 5180, and AFGL 490, shock features associated H 2 with molecular (CO) outÑows are observed. We have discovered faint, though extensive, bow shocks in the W75 N outÑow that indicate a total Ñow length of at least 3 pc. The Herbig-Haro knots that make up the HH 251È254 outÑow in S140 N are also observed in in addition, knots in the counterÑow H 2 ; are discovered. Copious emission is also observed throughout the NGC 7538 region ; Ðlamentary H 2 structures to the northeast of the central cluster (IRS 1) are probably photodissociation fronts, although a jetlike structure is observed associated with the IRS 9 CO outÑow. In AFGL 5180, a new, collimated jet is discovered to the east of the central cluster, and numerous knots and Ðlaments are observed H 2 around the cluster itself that could be associated with the known CO outÑow there. Last, line emis-H 2 sion is observed southwest of AFGL 490 ; in particular, a bright peak is found associated with a warm molecular clump in the CO outÑow.

The flattened, rotating molecular gas core of protostellar jet HH 212

The Astrophysical …, 2001

The recently discovered protostellar jet known as HH212 is beautifully symmetric, with a series of paired shock knots and bow shocks on either side of the exciting source region, IRAS 05413-0104 (Zinnecker et al. 1998). We present VLA ammonia maps of the IRAS 05413-0104 molecular gas envelope in which the protostellar jet source is embedded. We find that the envelope, with mass of 0.2 M ⊙ detected by the interferometer, is flattened perpendicular to the jet axis with a FWHM diameter of 12000 AU and an axis ratio of 2:1, as seen in NH 3 (1,1) emission. There is a velocity gradient of about 4-5 km sec −1 pc −1 across the flattened disk-like core, suggestive of rotation around an axis aligned with the jet. Flux-weighted mean velocities increase smoothly with radius with a roughly constant velocity gradient. In young (Class 0) systems such as HH212, a significant amount of material is still distributed in a large surrounding envelope, and thus the observable kinematics of the system may reflect the less centrally condensed, youthful state of the source and obscuration of central dynamics. The angular momentum of this envelope material may be released from infalling gas through rotation in the HH212 jet, as recent observations suggest (Davis et al. 2000). A blue-shifted wisp or bowl of emitting gas appears to be swept up along the blue side of the outflow, possibly lining the cavity of a wider angle wind around the more collimated shock jet axis. Our ammonia (2,2)/(1,1) ratio map indicates that this very cold core is heated to 14 Kelvin degrees in a centrally condensed area surrounding the jet source. This edge-on core and jet system appears to be young and deeply embedded. This environment, however, is apparently not disrupting the pristine symmetry and collimation of the jet.

A Hot Molecular Outflow Driven by the Ionized Jet Associated with Iras 16562–3959

The Astrophysical Journal, 2011

We report molecular line observations in the CO J=3→2, 6→5 and 7→6 transitions, made using the Atacama Pathfinder Experiment Telescope (APEX), toward the massive and dense core IRAS 16562−3959. This core harbors a string of radio sources thought to be powered by a central collimated jet of ionized gas. The molecular observations show the presence of high velocity gas exhibiting a quadrupolar morphology, most likely produced by the presence of two collimated outflows. The southeast-northwest molecular outflow is aligned with the string of radio continuum sources, suggesting it is driven by the jet. We find that the excitation temperature of the gas in the SE-NW outflow is high, with values of 145 and 120 K for the blueshifted and redshifted lobes, respectively. This outflow has a total mass of 1.92 M ⊙ , a total momentum of ∼ 89 M ⊙ km s −1 and an averaged momentum rate of ∼ 3.0 × 10 −2 M ⊙ km s −1 yr −1 , values characteristics of flows driven by young massive stellar objects with high luminosities (L bol ∼ 2 × 10 4 L ⊙). Complementary data taken with the Atacama Submillimeter Telescope Experiment (ASTE) in high density and shock tracers support the picture that IRAS 16562−3959 is an accreting young massive star associated with an ionized jet, which is the energy source of a molecular outflow.

HST observations of the protoplanetary nebula OH?231.8+4.2: The structure of the jets and shocks

Astronomy and Astrophysics, 2002

We present high-resolution images obtained with the WFPC2, on board the HST, of the protoplanetary nebula (PPN) OH 231.8+4.2. Hα and NII line emission and scattered light in the continuum at 6750 and 7910Å were observed. We also discuss NIR NICMOS images from the HST archive. The images show with high accuracy the shape and excitation state of the shocks developed in the nebula. Our high-resolution images (and data from other works) allow a very detailed and quantitative description of the different nebular components and of the physical conditions in them. We interpret specific structures identified in our images using existing models of shock interaction. In the center of the nebula, there is a dense torus-or disk-like condensation continued by an hourglass-like structure, with relatively high densities (∼10 5-10 6 cm −3) and temperatures (∼30 K). Inside this torus we have identified the location of the central star, from SiO maser observations. Two shock regions are detected from the optical line emission images, respectively in the north and south lobes. In both regions, a forward and a backward shock are identified. The densities of this hot gas vary between 40 and 250 cm −3 , with the densest clumps being placed in the reverse shocks. The total mass of the shocked hot gas is ∼2×10 −3 M , both lobes showing similar masses in spite of their different extents. The relatively collimated jet that impinges on an originally slow shell, so producing the shocks, is identified from the scattered light images and in CO maps. This flow is significantly denser and cooler than the shocked Hα regions. Its density decreases with the distance to the star, with typical values ∼10 5-10 4 cm −3 , and its temperature ranges between about 25 and 8 K. We explain the high Hα emission of the backward shock assuming that it propagates in a diffuse gas component, entrained by the observed collimated flow and sharing its axial movement. The existence of shocks also in the collimated densest flow is suggested by the high abundance of some molecules like HCO + and its structure and kinematics in certain regions, but they are not seen in Hα emission, probably because of the absence of (well developed) hot components in this dense flow. We think that the exceptionally detailed and quantitative image derived for the wind interaction regions in OH 231.8+4.2 is a challenge to check and improve hydrodynamical models of wind interaction in PPNe.