Shocks in dense clouds

Guillet, V.; Jones, A. P.; Forêts, G. Pineau des

doi:10.1051/0004-6361/200811115

Cited by 99 publications

(125 citation statements)

References 24 publications

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“…Guillet et al 2009Guillet et al , 2011. Anderl et al (2013) have shown that including them does not significantly alter the predicted OH emission of C-type models with n H of the order of 10 5 cm −3 (see their Fig.…”

Section: Scenario 1: One Outflow Two Shock Layersmentioning

confidence: 98%

Challenging shock models with SOFIA OH observations in the high-mass star-forming region Cepheus A

Güsten

Menten

Flower

et al. 2015

A&A

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Context. OH is a key molecule in H 2 O chemistry, a valuable tool for probing physical conditions, and an important contributor to the cooling of shock regions around high-mass protostars. OH participates in the re-distribution of energy from the protostar towards the surrounding Interstellar Medium. Aims. Our aim is to assess the origin of the OH emission from the Cepheus A massive star-forming region and to constrain the physical conditions prevailing in the emitting gas. We thus want to probe the processes at work during the formation of massive stars. Methods. We present spectrally resolved observations of OH towards the protostellar outflows region of Cepheus A with the GREAT spectrometer onboard the Stratospheric Observatory for Infrared Astronomy (SOFIA) telescope. Three triplets were observed at 1834.7 GHz, 1837.8 GHz, and 2514.3 GHz (163.4 µm, 163.1 µm between the 2 Π 1/2 J = 3/2 and J = 1/2 states, and 119.2 µm, a ground transition between the 2 Π 3/2 J = 5/2 and J = 3/2 states), at angular resolutions of 16. 3, 16. 3, and 11. 9, respectively. We also present the CO (16-15) spectrum at the same position. We compared the integrated intensities in the redshifted wings to the results of shock models. Results. The two OH triplets near 163 µm are detected in emission, but with blending hyperfine structure unresolved. Their profiles and that of can be fitted by a combination of two or three Gaussians. The observed 119.2 µm triplet is seen in absorption, since its blending hyperfine structure is unresolved, but with three line-of-sight components and a blueshifted emission wing consistent with that of the other lines. The OH line wings are similar to those of CO, suggesting that they emanate from the same shocked structure. Conclusions. Under this common origin assumption, the observations fall within the model predictions and within the range of use of our model only if we consider that four shock structures are caught in our beam. Overall, our comparisons suggest that all the observations might be consistently fitted by a J-type shock model with a high pre-shock density (n H > 10 5 cm −3 ), a high shock velocity ( s 25 km s −1 ), and with a filling factor of the order of unity. Such a high pre-shock density is generally found in shocks associated to high-mass protostars, contrary to low-mass ones.

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Section: Scenario 1: One Outflow Two Shock Layersmentioning

confidence: 98%

Challenging shock models with SOFIA OH observations in the high-mass star-forming region Cepheus A

Güsten

Menten

Flower

et al. 2015

A&A

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“…If confirmed as characteristic of massive star formation processes, such a high ratio could be accounted for by considering grain-grain interactions within the shock layer. Such interactions have been described as important at high pre-shock densities, and their feedback effects on both the chemical and dynamical structure of shocks have been studied by Guillet et al (2007Guillet et al ( , 2009Guillet et al ( , 2011. Unfortunately, those authors could not generate any selfconsistent solution for the pre-shock densities at work here, namely for n H = 10 6 cm −3 .…”

Section: Slab-lvg Analysismentioning

confidence: 99%

Evidence of a SiO collimated outflow from a massive YSO in IRAS 17233–3606

Leurini

Codella

Gusdorf

et al. 2013

A&A

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Studies of molecular outflows in high-mass young stellar objects reveal important information about the formation process of massive stars. We therefore selected the close-by IRAS 17233-3606 massive star-forming region to perform SiO observations with the SMA interferometer in the (5−4) line and with the APEX single-dish telescope in the (5−4) and (8-7) transitions. In this paper, we present a study of one of the outflows in the region, OF1, which shows several properties similar to jets driven by low-mass protostars, such as HH211 and HH212. It is compact and collimated, and associated with extremely high velocity CO emission, and SiO emission at high velocities. We used a state-of-the-art shock model to constrain the pre-shock density and shock velocity of OF1. The model also allowed us to self-consistently estimate the mass of the OF1 outflow. The shock parameters inferred by the SiO modelling are comparable with those found for low-mass protostars, only with higher pre-shock density values, yielding an outflow mass in agreement with those obtained for molecular outflows driven by early B-type young stellar objects. Our study shows that it is possible to model the SiO emission in high-mass star-forming regions in the same way as for shocks from low-mass young stellar objects.

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“…The gas-phase abundance of these species is strongly depleted in the ISM with respect to solar abundances because their atoms are locked onto dust grains (Savage & Sembach 1996). When dust grains evaporate in the launching region or are sputtered in shocks along the jet, these species are released into the gas-phase (Jones et al 1994;Jones 2000;May et al 2000;Draine 2004;Guillet et al 2009Guillet et al , 2011. Gas phase depletion of refractory elements has been observed by Nisini et al (2005) and Podio et al (2006Podio et al ( , 2009Podio et al ( , 2011 in HH jets from Class I sources at large distances from their driving source.…”

Section: Dust Contentmentioning

confidence: 99%

Relating jet structure to photometric variability: the Herbig Ae star HD 163296

Ellerbroek

Podio

Dougados

et al. 2014

A&A

131

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Herbig Ae/Be stars are intermediate-mass pre-main sequence stars surrounded by circumstellar dust disks. Some are observed to produce jets, whose appearance as a sequence of shock fronts (knots) suggests a past episodic outflow variability. This "jet fossil record" can be used to reconstruct the outflow history. We present the first optical to near-infrared (NIR) spectra of the jet from the Herbig Ae star HD 163296, obtained with VLT/X-shooter. We determine the physical conditions in the knots and also their kinematic "launch epochs". Knots are formed simultaneously on either side of the disk, with a regular interval of ∼16 yr. The velocity dispersion versus jet velocity and the energy input are comparable between both lobes. However, the mass-loss rate, velocity, and shock conditions are asymmetric. We findṀ jet /Ṁ acc ∼ 0.01−0.1, which is consistent with magneto-centrifugal jet launching models. No evidence of any dust is found in the high-velocity jet, suggesting a launch region within the sublimation radius (<0.5 au). The jet inclination measured from proper motions and radial velocities confirms that it is perpendicular to the disk. A tentative relation is found between the structure of the jet and the photometric variability of the central source. Episodes of NIR brightening were previously detected and attributed to a dusty disk wind. We report for the first time significant optical fadings lasting from a few days up to a year, coinciding with the NIR brightenings. These are very likely caused by dust lifted high above the disk plane, and this supports the disk wind scenario. The disk wind is launched at a larger radius than the high-velocity atomic jet, although their outflow variability may have a common origin. No significant relation between outflow and accretion variability could be established. Our findings confirm that this source undergoes periodic ejection events, which may be coupled with dust ejections above the disk plane.

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Shocks in dense clouds

Cited by 99 publications

References 24 publications

Challenging shock models with SOFIA OH observations in the high-mass star-forming region Cepheus A

Challenging shock models with SOFIA OH observations in the high-mass star-forming region Cepheus A

Evidence of a SiO collimated outflow from a massive YSO in IRAS 17233–3606

Relating jet structure to photometric variability: the Herbig Ae star HD 163296

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