Detection of Water in the Shocked Gas Associated with IC 443: Constraints on Shock Models

Snell, R. L.; Hollenbach, D. J.; Howe, J. E.; Neufeld, David A.; Kaufman, Michael J.; Melnick, Gary J.; Bergin, Edwin A.; Wang, Z.

doi:10.1086/427231

Cited by 80 publications

(107 citation statements)

References 50 publications

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“…In some cases, OH maser emission may be associated with shocked molecular clumps. For IC 443, for example, Snell et al (2005) detected the shocked clumps B, C, and G in H 2 O, 13 CO, and C I line emission with Submillimeter Wave Astronomy Satellite (SWAS) detectors. They concluded that, to explain these observations, different type shocks with a range of velocities is likely required.…”

Section: Radiative Shocksmentioning

confidence: 99%

Supernova Remnants Interacting with Molecular Clouds: X-Ray and Gamma-Ray Signatures

et al. 2014

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The giant molecular clouds (MCs) found in the Milky Way and similar galaxies play a crucial role in the evolution of these systems. The supernova explosions that mark the death of massive stars in these regions often lead to interactions between the supernova remnants (SNRs) and the clouds. These interactions have a profound effect on our understanding of SNRs. Shocks in SNRs should be capable of accelerating particles to cosmic ray (CR) energies with efficiencies high enough to power Galactic CRs. X-ray and γ-ray studies have established the presence of relativistic electrons and protons in some SNRs and provided strong evidence for diffusive shock acceleration as the primary acceleration mechanism, including strongly amplified magnetic fields, temperature and ionization effects on the shock-heated plasmas, and modifications to the dynamical evolution of some systems. Because protons dominate the overall energetics of the CRs, it is crucial to understand this hadronic component even though electrons are much more efficient radiators and it can be difficult to identify the hadronic component. However, near MCs the densities are sufficiently high to allow the γ-ray emission to be dominated by protons. Thus, these interaction sites provide some of our best opportunities to constrain the overall energetics of these particle accelerators. Here we summarize some key properties of interactions between SNRs and MCs, with an emphasis on recent X-ray and γ-ray studies that are providing important constraints on our understanding of cosmic rays in our Galaxy.

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Section: Radiative Shocksmentioning

confidence: 99%

Supernova Remnants Interacting with Molecular Clouds: X-Ray and Gamma-Ray Signatures

et al. 2014

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“…Santangelo et al 2013;Busquet et al 2014) than the value of ∼10 −4 expected if all oxygen is forced into water by warm gas-phase chemistry. It is unlikely that H 2 O could be converted into other species more efficiently at the off-source positions because the reaction rates for H 2 O reacting with H or any other species are low (Snell et al 2005;McElroy et al 2013). The gas-phase H 2 O abundance could be lower at the shock spots if sputtering is less efficient at the off-source positions because the velocity or density is lower (Caselli et al 1997).…”

Section: On Source Vs Off Sourcementioning

confidence: 99%

Water in star-forming regions withHerschel(WISH)

Mottram

Kristensen

Dishoeck

et al. 2014

A&A

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Context. Outflows are an important part of the star formation process as both the result of ongoing active accretion and one of the main sources of mechanical feedback on small scales. Water is the ideal tracer of these effects because it is present in high abundance for the conditions expected in various parts of the protostar, particularly the outflow. Aims. We constrain and quantify the physical conditions probed by water in the outflow-jet system for Class 0 and I sources. Methods. We present velocity-resolved Herschel HIFI spectra of multiple water-transitions observed towards 29 nearby Class 0/I protostars as part of the WISH guaranteed time key programme. The lines are decomposed into different Gaussian components, with each component related to one of three parts of the protostellar system; quiescent envelope, cavity shock and spot shocks in the jet and at the base of the outflow. We then use non-LTE radex models to constrain the excitation conditions present in the two outflow-related components. Results. Water emission at the source position is optically thick but effectively thin, with line ratios that do not vary with velocity, in contrast to CO. The physical conditions of the cavity and spot shocks are similar, with post-shock H 2 densities of order 10 5 −10 8 cmand H 2 O column densities of order 10 16 −10 18 cm −2 . H 2 O emission originates in compact emitting regions: for the spot shocks these correspond to point sources with radii of order 10−200 AU, while for the cavity shocks these come from a thin layer along the outflow cavity wall with thickness of order 1−30 AU. Conclusions. Water emission at the source position traces two distinct kinematic components in the outflow; J shocks at the base of the outflow or in the jet, and C shocks in a thin layer in the cavity wall. The similarity of the physical conditions is in contrast to off-source determinations which show similar densities but lower column densities and larger filling factors. We propose that this is due to the differences in shock properties and geometry between these positions. Class I sources have similar excitation conditions to Class 0 sources, but generally smaller line-widths and emitting region sizes. We suggest that it is the velocity of the wind driving the outflow, rather than the decrease in envelope density or mass, that is the cause of the decrease in H 2 O intensity between Class 0 and I sources.

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“…The major competing coolant to O i in a fast, dissociative shock is OH (Neufeld & Dalgarno 1989), and it is therefore likely that some of the OH emission is caused by the jet shock impinging on the inner, dense envelope. Further modelling, including combinations of C-and J-type shocks (Snell et al 2005), will be explored to constrain the origin of the OH emission. Table 3 summarizes the assigment of the various species to the different proposed physical components.…”

Section: Ohmentioning

confidence: 99%

Origin of the hot gas in low-mass protostars

Kempen

Kristensen²,

Herczeg

et al. 2010

A&A

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Aims. "Water In Star-forming regions with Herschel" (WISH) is a Herschel key programme aimed at understanding the physical and chemical structure of young stellar objects (YSOs) with a focus on water and related species. [O i] emission is seen in low-velocity gas, assumed to be related to the envelope, and is also seen shifted up to 170 km s −1 in both the red-and blue-shifted jets. Envelope models are constructed based on previous observational constraints. They indicate that passive heating of a spherical envelope by the protostellar luminosity cannot explain the high-excitation molecular gas detected with PACS, including CO lines with upper levels at >2500 K above the ground state. Instead, warm CO and H 2 O emission is probably produced in the walls of an outflow-carved cavity in the envelope, which are heated by UV photons and non-dissociative C-type shocks. The bright OH and [O i] emission is attributed to J-type shocks in dense gas close to the protostar. In the scenario described here, the combined cooling by far-IR lines within the central spatial pixel is estimated to be 2 × 10 −2 L , with 60-80% attributed to J-and C-type shocks produced by interactions between the jet and the envelope.

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Detection of Water in the Shocked Gas Associated with IC 443: Constraints on Shock Models

Cited by 80 publications

References 50 publications

Supernova Remnants Interacting with Molecular Clouds: X-Ray and Gamma-Ray Signatures

Supernova Remnants Interacting with Molecular Clouds: X-Ray and Gamma-Ray Signatures

Water in star-forming regions withHerschel(WISH)

Origin of the hot gas in low-mass protostars

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