Revisiting the shocks in BHR71: new observational constraints and H<sub>2</sub>O predictions for<i>Herschel</i>

Giannini, T.; Flower, D. R.; Parise, B.; Güsten, R.; Kristensen, L. E.

doi:10.1051/0004-6361/201116758

Cited by 26 publications

(41 citation statements)

References 51 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This is consistent with the fact that the SiO emission detected so far in low-mass star-forming regions is associated with high-velocity protostellar outflows, either as broad SiO emission, or as narrow emission with a velocity peak offset from systemic velocities (e.g. Gueth et al 1998;Nisini et al 2007;Gusdorf et al 2011;Gómez-Ruiz et al 2013).…”

Section: Origin Of the Narrow Sio Emissionsupporting

confidence: 85%

SiO emission from low- and high-velocity shocks in Cygnus-X massive dense clumps

Duarte-Cabral¹,

Bontemps²,

Motte³

et al. 2014

A&A

Self Cite

View full text Add to dashboard Cite

Context. The SiO molecule is formed through interstellar shocks and is often used as a tracer of high-velocity shocks from protostellar outflows. However, recent studies have suggested that low-velocity shocks in the interstellar medium can be responsible for a significant amount of SiO emission observed in star-forming regions. Aims. We aim to investigate the existence of SiO emission that may or may not be associated with outflow shocks, within several massive dense clumps (MDCs), and explore how the SiO luminosities compare with the outflow properties estimated using CO. Methods. We used observations of SiO (2−1) from the Plateau de Bure Interferomètre, towards a sample of six MDCs in Cygnus-X, and compared them to the CO high-velocity outflow emission, and to the velocity shears found in these regions. Results. We find that most molecular outflows are detected in both SiO and CO, although there are some cases of CO outflows with no SiO counterpart. The data also shows narrow line SiO emission (σ 1.5 km s −1 ) which, in some cases, appears to be unrelated to outflows. The kinematics of this narrow emission often differs from those found by other high-density tracers such as H 13 CO + , and its extent varies from rather compact (∼0.03 pc) to widespread (∼0.2 pc). We find that the least centrally concentrated clumps with the least massive protostellar cores have the most widespread narrow SiO emission. The fraction of the total SiO luminosity that is not associated with outflows is highly variable in the different MDCs (from 10% to 90%); this might be a problem when extrapolating outflow properties from SiO luminosities without resolving individual outflows. Conclusions. In line with previous evidence of SiO emission associated with low-velocity shocks, we propose an evolutionary picture to explain the existence and distribution of narrow SiO line profiles. In this scenario, the least centrally condensed MDCs are at an early stage where the SiO emission traces shocks from the large-scale collapse of material onto the MDC. This could be the case of CygX-N40, a MDC with a low-mass protostar at its centre, a weak outflow, and where 90% of the SiO emission is narrow and arises from the outskirts. As the MDC collapses, the SiO emission becomes more confined to the close surroundings of cores, tracing the post-shock material from the infalling MDC against the dense cores, such as in the small-scale converging flows of CygX-N3, N12, and N48. At later stages, when single massive protostars are formed, as for instance in CygX-N53 and N63, the SiO luminosity is largely dominated by powerful outflows, and the weaker narrow component shows perhaps the last remnants of the initial collapse.

show abstract

Section: Origin Of the Narrow Sio Emissionsupporting

confidence: 85%

SiO emission from low- and high-velocity shocks in Cygnus-X massive dense clumps

Duarte-Cabral¹,

Bontemps²,

Motte³

et al. 2014

A&A

Self Cite

View full text Add to dashboard Cite

show abstract

“…These slow shocks are similar to shocks originating in bipolar outflows of very young stars (e.g. Gusdorf et al 2011): they strongly cool through molecular emission and can be observed in the far-IR and sub-mm wavelength regime (e.g. Neufeld et al 2007;Frail & Mitchell 1998).…”

Section: Introductionmentioning

confidence: 60%

APEX observations of supernova remnants

Anderl

Güsten

2014

A&A

Self Cite

View full text Add to dashboard Cite

Context. When supernova blast waves interact with nearby molecular clouds, they send slower shocks into these clouds. The resulting interaction regions provide excellent environments for the use of MHD shock models to constrain the physical and chemical conditions in these regions. Aims. The interaction of supernova remnants (SNRs) with molecular clouds gives rise to strong molecular emission in the far-IR and sub-mm wavelength regimes. The application of MHD shock models in the interpretation of this line emission can yield valuable information on the energetic and chemical impact of SNRs. Methods. New mapping observations with the APEX telescope in 12 CO (3-2), (4-3), (6-5), (7-6), and 13 CO (3-2) towards two regions in the SNR W44 are presented. Integrated intensities are extracted on five different positions, corresponding to local maxima of CO emission. The integrated intensities are compared to the outputs of a grid of models, which combine an MHD shock code with a radiative transfer module based on the large velocity gradient approximation. Results. All extracted spectra show ambient and line-of-sight components as well as blue-and red-shifted wings indicating the presence of shocked gas. Basing the shock model fits only on the highest-lying transitions that unambiguously trace the shock-heated gas, we find that the observed CO line emission is compatible with non-stationary shocks and a pre-shock density of 10 4 cm −3 . The ages of the modelled shocks scatter between values of ∼1000 and ∼3000 years. The shock velocities in W44F are found to lie between 20 km s −1 and 25 km s −1 , while in W44E fast shocks (30-35 km s −1 ) as well as slower shocks (∼20 km s −1 ) are compatible with the observed spectral line energy diagrams. The pre-shock magnetic field strength components perpendicular to the line of sight in both regions have values between 100 µG and 200 µG. Our best-fitting models allow us to predict the full ladder of CO transitions, the shocked gas mass in one beam as well as the momentum and energy injection.

show abstract

“…For instance, a microjet was recently imaged at high spatial resolution in the HH212 protostellar outflow by Codella et al (2014) in SiO and Podio et al (2015) in SO and SO 2 , without having a counterpart in H 2 emission at 2.12 µm. Our modelling method is the same as presented in Gusdorf et al (2011Gusdorf et al ( , 2012. The model is one-dimensional, can simulate the propagation of stationary C-and J-type shocks, and includes a self-consistent Large Velocity Gradient (LVG) treatment of the radiative transfer in the lines emitted by various cooling species (CO, H 2 O, SiO, NH 3 , and OH).…”

Section: Discussionmentioning

confidence: 99%

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

Güsten

Menten

Flower

et al. 2015

A&A

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Revisiting the shocks in BHR71: new observational constraints and H₂O predictions forHerschel

Cited by 26 publications

References 51 publications

SiO emission from low- and high-velocity shocks in Cygnus-X massive dense clumps

SiO emission from low- and high-velocity shocks in Cygnus-X massive dense clumps

APEX observations of supernova remnants

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

Contact Info

Product

Resources

About

Revisiting the shocks in BHR71: new observational constraints and H2O predictions forHerschel

Cited by 26 publications

References 51 publications

SiO emission from low- and high-velocity shocks in Cygnus-X massive dense clumps

SiO emission from low- and high-velocity shocks in Cygnus-X massive dense clumps

APEX observations of supernova remnants

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

Contact Info

Product

Resources

About

Revisiting the shocks in BHR71: new observational constraints and H₂O predictions forHerschel