Spitzer spectral line mapping of the HH211 outflow (original) (raw)

ATOMIC JETS FROM CLASS 0 SOURCES DETECTED BY SPITZER : THE CASE OF L1448-C

The Astrophysical Journal, 2009

We present Spitzer-IRS spectra obtained along the molecular jet from the Class 0 source L1448-C (or L1448-mm). Atomic lines from the fundamental transitions of [FeII], [SiII] and [SI] have been detected showing, for the first time, -2the presence of an embedded atomic jet at low excitation. Pure rotational H 2 lines are also detected, and a decrease of the atomic/molecular emission ratio is observed within 1 ′ from the driving source. Additional ground based spectra (UKIRT/UIST) were obtained to further constrain the H 2 excitation along the jet axis and, combined with the 0-0 lines, have been compared with bow-shock models. From the different line ratios, we find that the atomic gas is characterized by an electron density n e ∼ 200-1000 cm −3 , a temperature T e < 2500 K and an ionization fraction 10 −2 ; the excitation conditions of the atomic jet are thus very different from those found in more evolved Class I and Class II jets. We also infer that only a fraction (0.05-0.2) of Fe and Si is in gaseous form, indicating that dust still plays a major role in the depletion of refractory elements. A comparison with the SiO abundance recently derived in the jet from an analysis of several SiO sub-mm transitions, shows that the Si/SiO abundance ratio is ∼100, and thus that most of the silicon released from grains by sputtering and grain-grain collisions remains in atomic form. Finally, estimates of the atomic and molecular mass flux rates have been derived: values of the order of ∼10 −6 and ∼10 −7 M ⊙ yr −1 are inferred from the [SI]25µm and H 2 line luminosities, respectively. A comparison with the momentum flux of the CO molecular outflow suggests that the detected atomic jet has the power to drive the large scale outflow.

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.

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.

SiO J=5--4 in the HH211 Protostellar Jet Imaged with the SMA

2005

We have mapped the SiO J=5-4 line at 217GHz from the HH211 molecular outflow with the Submillimeter Array (SMA). The high resolution map (1.6''x0.9'') 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 Chandler & Richer (2001) suggests that these knots have a temperature in excess of 300-500 K and a density of (0.5-1) x10^7 cm^{-3}. The radial velocity measured for these knots is ~30 km/s, 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.

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.

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.

HH 223: a parsec-scale H 2 outflow in the star-forming region L723

Astronomy & Astrophysics, 2010

Context. The dark cloud Lynds 723 (L723) is a low-mass star-forming region where one of the few known cases of a quadrupolar CO outflow has been reported. Two recent works have found that the radio continuum source VLA 2, towards the centre of the CO outflow, is actually a multiple system of young stellar objects (YSOs). Several line-emission nebulae that lie projected on the eastwest CO outflow were detected in narrow-band Hα and [S ii] images. The spectra of the knots are characteristic of shock-excited gas (Herbig-Haro spectra), with supersonic blueshifted velocities, which suggests an optical outflow also powered by the VLA 2 YSO system of L723. Aims. Our aim is to study L723 in the near-infrared and look for line-emission nebulae associated with the optical and CO outflows. Methods. We imaged a field of ∼ 5 × 5 centred on HH 223, which includes the whole region of the quadrupolar CO outflow with narrow-band filters centred on the [Fe ii] 1.644 µm and H 2 2.122 µm lines, together with off-line H c and K c filters. The [Fe ii] and H 2 line-emission structures were identified after extracting the continuum contribution, if any. Their positions were determined from an accurate astrometry of the images. Results. The H 2 line-emission structures appear distributed over a region of 5. 5 (∼ 0.5 pc for a distance of 300 pc) at both sides of the VLA 2 YSO system, with an S-shape morphology, and are projected onto the east-west CO outflow. Most of them were resolved in smaller knotty substructures. The [Fe ii] emission only appears associated with HH 223. An additional nebular emission from the continuum in H c and K c appears associated with HH 223-K1, the structure closest to the VLA 2 YSO system, and could be tracing the cavity walls. Conclusions. We propose that the H 2 structures form part of a large-scale near-infrared outflow, which is also associated with the VLA 2 YSO system. The current data do not allow us to discern which of the YSOs of VLA 2 is powering this large scale optical/nearinfrared outflow.

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.