Spitzer and Near-Infrared Observations of a New Bipolar Protostellar Outflow in the Rosette Molecular Cloud (original) (raw)
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The near-infrared excitation of the HH?211 protostellar outflow
Astronomy and Astrophysics, 2005
The protostellar outflow HH 211 is of considerable interest since it is extremely young and highly collimated. Here, we explore the outflow through imaging and spectroscopy in the near-infrared to determine if there are further diagnostic signatures of youth. We confirm the detection of a near-infrared continuum of unknown origin. We propose that it is emitted by the driving millimeter source, escapes the core through tunnels, and illuminates features aligning the outflow. Narrow-band flux measurements of these features contain an unusually large amount of continuum emission.
A New Look at Stellar Outflows: Spitzer Observations of the HH 46/47 System
The Astrophysical Journal Supplement Series, 2004
We present the Early Release Observations of the HH 46/47 system and HH 46 IRS 1 source, taken with the three instruments aboard the Spitzer Space Telescope. The optically invisible southwest lobe, driven by the HH 47C bow shock, is revealed in full detail by the Infrared Array Camera (IRAC) images and displays a ''loop''-like morphology. Both of the mid-infrared outflow lobes are narrower than those of CO flow. We believe that the combination of emission by H 2 rotational lines [S(11)-S(4)] and some atomic lines, which fall within the IRAC passbands, are responsible for the bulk of the observed emission, although contributions from the 3.3, 6.2, and 7.7 m polycyclic aromatic hydrocarbon emission bands cannot be ruled out. Weak spectral features corresponding to these emitters are present in the Infrared Spectrograph spectrum of the HH 47A bow shock. The spectrum of HH 46 IRS 1 shows remarkable similarities to those of high-mass protostars, which include the presence of H 2 O, CO 2 , CH 4 , and possibly NH 3 , CH 3 OH, and NH þ 4 ices. The high ice abundances and the lack of signs of thermal processing indicate that these ices in the envelope are well shielded from the powerful outflow and its cavity. Emission from the Bok globule at 24 m is detected and displays a similar structure to that observed at 8 m.
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.
Monthly Notices of the Royal Astronomical Society, 2000
CO J 3±2 and 4±3 observations of V380 Ori-NE reveal a highly collimated bipolar molecular outflow associated with a jet traced here in H 2 1±0 S(1) line emission. The source of the flow is also detected at 450 and 850 mm with SCUBA. The combined CO and near-IR observations offer compelling support for the prompt entrainment model of jet-driven molecular outflows. Not only are the H 2 shock fronts spatially coincident with peaks in the CO outflow lobes, but the slope of the mass±velocity distribution in the flow, measured here at intervals along both flow lobes, also clearly decreases just behind the advancing shock fronts (and towards the ends of the flow lobes), as one would expect if the high-to-low velocity mass fraction was enhanced by the entraining shocks.
Near-infrared imaging of H2 in molecular outflows from young stars
Astrophysics and Space Science, 1995
A b s t r a c t . In an attempt to identify the molecular shocks associated with the entrainment of ambient gas by collimated stellar winds from young stars, we have imaged a number of known molecular outflows in H2 v = l -0 S(1) and wide-band K. In each flow, the observed H2 features are closely associated with peaks in the CO outflow maps. We therefore suggest that the Hz results from shocks associated with the acceleration or entrainment of ambient, molecular gas. This molecular material may be accelerated either in a bow shock at the head of the flow, or along the length of the flow through a turbulent mixing layer.
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.
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.
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.
H2 observations of outflows from young stars
Analizamos observaciones del IR cercano recientes de jets Herbig-Haro (HH) y de flujos moleculares de protoestrellas muy jóvenes profundamente embebidas. Mediciones de movimiento propio y estudios espectroscópicos de baja y de alta resolución muestran la excitación y la cinemática de objetos individuales, que podrían interpretarse en términos de choques de proa de alta velocidad que barren y incorporan material del ambiente para formar flujos moleculares de "CO". Las propiedades observadas de muchos objetos puede explicarse razonablemente bien con modelos de choques de proa tipo "C" magnetizados, aunque choques del tipo "J" no puede excluirse del todo. Analizamos también nuevas observaciones echelle de las fuentes mismas de los flujos. Estos datos de H 2 muestran emisión de línea de velocidades intermedias y altas en la base del flujo (de menos de unas pocos cientos de unidades astronómicas de la fuente que lo impulsa) en la mayoría de las fuentes observadas. Las propiedades de estas regiones de líneas de emisión de hidrógeno molecular-o MHEL, por sus siglas en inglés-son similares a las regiones de líneas prohibidas (FEL, por sus siglas en inglés) hacia estrellas T Tauri.
Discovery of a molecular outflow, near-infrared jet and HH objects towards IRAS 06047-1117
Astronomy and Astrophysics, 2001
We report discovery of a new young stellar object driving a point-symmetric, near-infrared jet and molecular outflow. The YSO is associated with IRAS 06047-1117 and is embedded in a dense molecular cloud core located southeast of Orion A. The jet is seen in the H2 v=1-0 line at 2.12 mu m and extends over a total length of about ~