CH+ and SH+ in the diffuse interstellar medium: Tracers of turbulent dissipation

2015 ◽  
Author(s):  
Falgarone Edith ◽  
Godard Benjamin ◽  
Gerin Maryvonne ◽  
De Luca Massimo
Keyword(s):  
Interstellar Medium ◽  
Turbulent Dissipation

scholarly journals Molecular richness of the diffuse interstellar medium: a signpost of turbulent dissipation

2012 ◽  
Vol 8 (S292) ◽  
pp. 223-226
Author(s):  
Edith Falgarone ◽  
Benjamin Godard ◽  
Guillaume Pineau des Forêts ◽  
Maryvonne Gerin
Keyword(s):  
Interstellar Medium ◽  
Absorption Spectroscopy ◽  
Molecular Cloud ◽  
Additional Source ◽  
Turbulent Dissipation ◽  
Molecular Fraction

AbstractThe Herschel/HIFI absorption spectroscopy surveys reveal the unexpected molecular richness of the Galactic diffuse ISM, even in gas of very low average H2 molecular fraction. In particular, two hydrides, CH+ and SH+ with highly endoergic formation routes have abundances that challenge models of UV-driven chemistry. The intermittent dissipation of turbulence appears as a plausible additional source of energy for the diffuse ISM chemistry. We present recent results of the so-called models of Turbulent Dissipation Regions (TDR). The abundances of many of the molecules observed in the diffuse ISM, including CO that is used as a tracer of the molecular cloud mass, may be understood in the framework of the TDR models.

scholarly journals Atomic and Ionized Microstructures in the Diffuse Interstellar Medium

2018 ◽  
Vol 56 (1) ◽  
pp. 489-540 ◽  
Author(s):  
Snežana Stanimirović ◽  
Ellen G. Zweibel
Keyword(s):  
Interstellar Medium ◽  
Supernova Remnants ◽  
Spatial Scales ◽  
Physical Processes ◽  
Interstellar Gas ◽  
Local Bubble ◽  
Turbulent Dissipation ◽  
Atomic Structures ◽  
Discrete Structures ◽  
Turbulent Cascade

It has been known for half a century that the interstellar medium (ISM) of our Galaxy is structured on scales as small as a few hundred kilometers, more than 10 orders of magnitude smaller than typical ISM structures and energy input scales. In this review we focus on neutral and ionized structures on spatial scales of a few to ∼104AU, which appear to be highly overpressured, as these have the most important role in the dynamics and energy balance of interstellar gas: the tiny scale atomic structures (TSASs) and extreme scattering events (ESEs) as the most overpressured example of the tiny scale ionized structures (TSISs). We review observational results and highlight key physical processes at AU scales. We present evidence for and against microstructures as part of a universal turbulent cascade and as discrete structures, and we review their association with supernova remnants, the Local Bubble, and bright stars. We suggest a number of observational and theoretical programs that could clarify the nature of AU structures. TSAS and TSIS probe spatial scales in the range of what is expected for turbulent dissipation scales and are therefore of key importance for constraining exotic and not-well-understood physical processes that have implications for many areas of astrophysics. The emerging picture is one in which a magnetized, turbulent cascade, driven hard by a local energy source and acting jointly with phenomena such as thermal instability, is the source of these microstructures.

scholarly journals Turbulence in the Diffuse Interstellar Medium

2011 ◽  
Vol 7 (S280) ◽  
pp. 187-202
Author(s):  
Edith Falgarone ◽  
Benjamin Godard ◽  
Pierre Hily-Blant
Keyword(s):  
Interstellar Medium ◽  
Large Scale ◽  
Line Emission ◽  
Turbulent Energy ◽  
Velocity Shear ◽  
Rotational Line ◽  
Turbulent Dissipation ◽  
Energy Cascades ◽  
Velocity Increments ◽  
Non Gaussian

AbstractThe diffuse interstellar medium (ISM) hosts the first steps of interstellar chemistry and the seeds of dense structures. Since its turbulent pressure by far exceeds its thermal pressure, turbulence must play a prominent role in its evolution. Fed at galactic scales, turbulent energy cascades down to the dissipation scales, but as in both laboratory and atmospheric turbulence, it does so in an intermittent way : only a tiny fraction of the small-scales is fed by the turbulent cascade, so that dissipation occurs in bursts. In diffuse molecular clouds, where they can be observed, the signatures of intermittency are: (1) the non-Gaussian statistics of velocity increments, and (2) the existence of coherent structures of intense velocity-shear that appear to channel the large-scale turbulent energy down to milliparsec scales. Attempts at modelling the warm chemistry triggered in the diffuse ISM by bursts of turbulent dissipation are promising : in this framework, the so far unexplained molecular richness observed in this medium is naturally understood, in particular its CH+, HCO+ and CO abundances. Turbulent dissipation is also likely at the origin of the H2 rotational line emission of the diffuse ISM and of a significant fraction of its [C II] emission.

scholarly journals Molecular richness of the diffuse interstellar medium: a signpost of turbulent dissipation

2012 ◽  
Vol 10 (H16) ◽  
pp. 603-605
Author(s):  
Edith Falgarone ◽  
Benjamin Godard ◽  
Guillaume Pineau des Forêts ◽  
Maryvonne Gerin
Keyword(s):  
Interstellar Medium ◽  
Absorption Spectroscopy ◽  
Molecular Clouds ◽  
Additional Source ◽  
Turbulent Dissipation ◽  
Molecular Fraction

AbstractThe Herschel/HIFI absorption spectroscopy surveys reveal the unexpected molecular richness of the Galactic diffuse ISM, even in gas of very low average H2 molecular fraction. In particular, two hydrides, CH+ and SH+ with highly endoenergetic formation routes have abundances that challenge models of UV-driven chemistry. The intermittent dissipation of turbulence appears as a plausible additional source of energy for the diffuse ISM chemistry. We present recent results of the so-called models of Turbulent Dissipation Regions (TDR). The abundances of many of the molecules observed in the diffuse ISM, including CO that is used as a tracer of the molecular clouds mass, may be understood in the framework of the TDR models.

scholarly journals Models of turbulent dissipation regions in the diffuse interstellar medium

2009 ◽  
Vol 495 (3) ◽  
pp. 847-867 ◽  
Author(s):  
B. Godard ◽  
E. Falgarone ◽  
G. Pineau des Forêts
Keyword(s):  
Interstellar Medium ◽  
Turbulent Dissipation

PRONAOS observations of the interstellar medium: New insights on interstellar Dust

2002 ◽  
Vol 4 ◽  
pp. 9-9
Author(s):  
I. Ristorcelli ◽  
B. Stepnik ◽  
X. Dupac ◽  
A. Abergel ◽  
J. P. Bernard ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Interstellar Dust
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