Low velocity shocks: signatures of turbulent dissipation in diffuse irradiated gas

Abstract

We examine the chemical and emission properties of mildly irradiated (G0=1) magnetised shocks in diffuse media (nH=10^2 to 10^4 /cm3) at low to moderate velocities (from 3 to 40 km/s). Results: The formation of some molecules relies on endoergic reactions. In J-shocks, their abundances are enhanced by several orders of magnitude for shock velocities as low as 7 km/s. Otherwise most chemical properties of J-type shocks vary over less than an order of magnitude between velocities from about 7 to about 30 km/s, where H2 dissociation sets in. C-type shocks display a more gradual molecular enhancement as the shock velocity increases. We quantify the energy flux budget (fluxes of kinetic, radiated and magnetic energies) with emphasis on the main cooling lines of the cold interstellar medium. Their sensitivity to shock velocity is such that it allows observations to constrain statistical distributions of shock velocities. We fit various probability distribution functions (PDFs) of shock velocities to spectroscopic observations of the galaxy-wide shock in Stephan's Quintet (SQ) and of a Galactic line of sight sampling diffuse molecular gas in Chamaeleon. In both cases, low velocities bear the greatest statistical weight and the PDF is consistent with a bimodal distribution. In the very low velocity shocks (below 5 km/s), dissipation is due to ion-neutral friction which powers H2 low energy transitions and atomic lines. In moderate velocity shocks (20 km/s and above), the dissipation is due to viscous heating and accounts for most of the molecular emission. In our interpretation a significant fraction of the gas on the line of sight is shocked (from 4% to 66%). For example, C+ emission may trace shocks in UV irradiated gas where C+ is the dominant carbon species.

In press, version prior to language edition, 15 pages, 19 figures

References in corpus (5)

• A Unified Representation of Gas-Phase Element Depletions in the Interstellar Medium
• Powerful High Velocity-Dispersion Molecular Hydrogen Associated with an Intergalactic Shock Wave in Stephan's Quintet
• Models of turbulent dissipation regions in the diffuse interstellar medium
• Modeling of diffuse molecular gas applied to HD 102065 observations
• Fluctuations of statistics among subregions of a turbulence velocity field

Cited by in corpus (53)

• Sulphur-bearing molecules in diffuse molecular clouds: new results from SOFIA/GREAT and the IRAM 30 m telescope
• Mid-Infrared Properties of Luminous Infrared Galaxies II: Probing the Dust and Gas Physics of the GOALS Sample
• Large turbulent reservoirs of cold molecular gas around high-redshift starburst galaxies
• Strong C+ emission in galaxies at z~1-2: Evidence for cold flow accretion powered star formation in the early Universe
• Models of irradiated molecular shocks
• Powerful H2 Line Cooling in Stephan's Quintet II. Group-wide Gas and Shock Modeling of the Warm H2 and a Comparison with [CII]157.7um Emission and Kinematics
• Tracing extended low-velocity shocks through SiO emission - Case study of the W43-MM1 ridge
• Modeling accretion shocks at the disk-envelope interface -- Sulfur chemistry
• Shock excitation of H${}_2$ in the James Webb Space Telescope era
• A SiO J = 5 - 4 Survey Toward Massive Star Formation Regions
• Strong Far-IR Cooling Lines, Peculiar CO Kinematics and Possible Star Formation Suppression in Hickson Compact Group 57
• Multi-phase gas interactions on subarcsec scales in the shocked IGM of Stephan's Quintet with JWST and ALMA
• Dense gas formation in the Musca filament due to the dissipation of a supersonic converging flow
• A train of shocks at 3000 au scale? Exploring the clash of an expanding bubble into the NGC 1333 IRAS 4 region. SOLIS XIV
• SHOCKFIND - An algorithm to identify magnetohydrodynamic shock waves in turbulent clouds
• Impacts of pure shocks in the BHR71 bipolar outflow
• Mid-J CO observations of Perseus B1-East 5: evidence for turbulent dissipation via low-velocity shocks
• Turbulent energy dissipation and intermittency in ambipolar diffusion magnetohydrodynamics
• Formation of dense structures induced by filament collisions. Correlation of density, kinematics and magnetic field in the Pipe nebula
• ALMA reveals Strong [CII] emission in a galaxy embedded in a giant Lyman-alpha blob at z=3.1
• Standing in the shadow of dark gas: ALMA observations of absorption from dark CO in the molecular DNM of Chamaeleon
• Self-generated ultraviolet radiation in molecular shock waves II. CH+ and the interpretation of emission from shock ensembles
• Unusually high HCO+/CO ratios in and outside supernova remnant W49B
• Experimental determination of the dissociative recombination rate coefficient for rotationally-cold CH${}^{+}$ and its implications for the diffuse cloud chemistry
• H${}_2$ emission from non-stationary magnetized bow shocks
• Mid-J CO Shock Tracing Observations of Infrared Dark Clouds III: SLED fitting
• Where infall meets outflows: turbulent dissipation probed by CH${}^{+}$ and Ly$\alpha$ in the starburst/AGN galaxy group SMM J02399$-$0136 at z$\sim$2.8
• The Close AGN Reference Survey (CARS). Discovery of a global [CII] 158 $\mu$m line excess in AGN HE1353-1917
• Discovery of a pre-existing molecular filament associated with supernova remnant G127.1+0.5
• SOFIA/EXES observations of warm H${}_2$ at high spectral resolution: witnessing para-to-ortho conversion behind a molecular shock wave in HH7
• Fundamental MHD scales -- II: the kinematic phase of the supersonic small-scale dynamo
• Probing the nature of dissipation in compressible MHD turbulence
• Dents in the Veil: Protostellar feedback in Orion
• The Unusual AGN Host NGC 1266: Evidence for Shocks in a Molecular Gas Rich S0 Galaxy with a Low Luminosity Nucleus
• Radiative and mechanical energies in galaxies I. Contributions of molecular shocks and PDRs in 3C 326 N
• The CO emission in the Taffy Galaxies (UGC 12914/5) at 60pc resolution-I: The battle for star formation in the turbulent Taffy Bridge
• FAUST XV. A disk wind mapped by CH${}_3$OH and SiO in the inner 300 au of the NGC 1333 IRAS 4A2 protostar
• The ALMA-CRISTAL survey: Extended [CII] emission in an interacting galaxy system at z ~ 5.5
• Shaken or stirred: the diffuse interstellar medium with exceptionally high SiO abundance
• [CII] and CO Emission Along the Bar and Counter-Arms of NGC 7479
• The interstellar medium in Andromeda's dwarf spheroidal galaxies: II. Multi-phase gas content and ISM conditions
• Shocks in the warm neutral medium I -- Theoretical model
• UV-irradiated outflows from low-mass protostars in Ophiuchus with JWST/MIRI
• Shocks and Molecules in Diffuse Interstellar Cloud Pairs
• Supernova Shocks in Molecular Clouds: Shocks Driven into Dense Cores in IC 443 and 3C 391
• Spinning Nanoparticles Impacted by C-shock: Implications for Radio-millimeter Emission from Star-forming Regions
• Measuring the ISM Content of Nearby, Luminous, Type 1 and Type 2 QSOs through CO and [C II]
• Shock-type inference of L1157 B2 using methanol desorption
• Properties of Interstellar Medium in the S0 Galaxy NGC 1222: Evidence for Shocked-enhanced Line Emission
• Rate Constants for Fine-Structure Excitations in O-H Collisions with Error Bars Obtained by Machine Learning
• CO Structures with Narrow Lines in Nearby Quiescent Regions
• Observations of ionized carbon towards the $\gamma$-ray-bright supernova remnant RX J1713.7-3946
• Infrared view of the multiphase ISM in NGC 253 II. Modelling the ionised and neutral atomic gas