Universität zu Köln

Robitaille, J-F, Motte, F., Schneider, N., Elia, D. and Bontemps, S. (2019). Exposing the plural nature of molecular clouds Extracting filaments and the cosmic infrared background against the true scale-free interstellar medium. Astron. Astrophys., 628. LES ULIS CEDEX A: EDP SCIENCES S A. ISSN 1432-0746

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Abstract

We present the Multiscale non-Gaussian Segmentation (MnGSeg) analysis technique. This wavelet-based method combines the analysis of the probability distribution function (PDF) of map fluctuations as a function of spatial scales and the power spectrum analysis of a map. This technique allows us to extract the non-Gaussianities identified in the multiscaled PDFs usually associated with turbulence intermittency and to spatially reconstruct the Gaussian and the non-Gaussian components of the map. This new technique can be applied on any data set. In the present paper, it is applied on a Herschel column density map of the Polaris flare cloud. The first component has by construction a self-similar fractal geometry similar to that produced by fractional Brownian motion (fBm) simulations. The second component is called the coherent component, as opposed to fractal, and includes a network of filamentary structures that demonstrates a spatial hierarchical scaling (i.e. filaments inside filaments). The power spectrum analysis of the two components proves that the Fourier power spectrum of the initial map is dominated by the power of the coherent filamentary structures across almost all spatial scales. The coherent structures contribute increasingly from larger to smaller scales, without producing any break in the inertial range. We suggest that this behaviour is induced, at least partly, by inertial-range intermittency, a well-known phenomenon for turbulent flows. We also demonstrate that the MnGSeg technique is itself a very sensitive signal analysis technique that allows the extraction of the cosmic infrared background (CIB) signal present in the Polaris flare submillimetre observations and the detection of a characteristic scale for 0.1 less than or similar to l less than or similar to 0.3 pc. The origin of this characteristic scale could partly be the transition of regimes dominated by incompressible turbulence versus compressible modes and other physical processes, such as gravity.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Robitaille, J-F UNSPECIFIED UNSPECIFIED UNSPECIFIED Motte, F. UNSPECIFIED UNSPECIFIED UNSPECIFIED Schneider, N. UNSPECIFIED UNSPECIFIED UNSPECIFIED Elia, D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Bontemps, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-144728
DOI:	10.1051/0004-6361/201935545
Journal or Publication Title:	Astron. Astrophys.
Volume:	628
Date:	2019
Publisher:	EDP SCIENCES S A
Place of Publication:	LES ULIS CEDEX A
ISSN:	1432-0746
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language DENSITY PROBABILITY-DISTRIBUTION; GALACTIC NEUTRAL HYDROGEN; INITIAL MASS FUNCTION; POWER SPECTRUM; STATISTICAL PROPERTIES; WAVELET TRANSFORMS; ELECTRON-DENSITY; STAR-FORMATION; DUST EMISSION; TURBULENCE Multiple languages Astronomy & Astrophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/14472