Characterizing the structure of diffuse emission in Hi-GAL maps

Abstract

We present a study of the structure of the Galactic interstellar medium through the Delta-variance technique, related to the power spectrum and the fractal properties of infrared/sub-mm maps. Through this method, it is possible to provide quantitative parameters which are useful to characterize different morphological and physical conditions, and to better constrain the theoretical models. In this respect, the Herschel Infrared Galactic Plane Survey carried out at five photometric bands from 70 to 500 μm constitutes an unique database for applying statistical tools to a variety of regions across the Milky Way. In this paper, we derive a robust estimate of the power-law portion of the power spectrum of four contiguous 2°x2° Hi-GAL tiles located in the third Galactic quadrant (217° < l < 225°, -2° < b < 0°). The low level of confusion along the line of sight testified by CO observations makes this region an ideal case. We find very different values of the power spectrum slope from tile to tile but also from wavelength to wavelength (2 < β< 3), with similarities between fields attributable to components located at the same distance. Thanks to the comparison with models of turbulence, an explanation of the determined slopes in terms of the fractal geometry is also provided, and possible relations with the underlying physics are investigated. In particular, an anti-correlation between ISM fractal dimension and star formation efficiency is found for the two main distance components observed in these fields. A possible link between the fractal properties of the diffuse emission and the resulting clump mass function is discussed.

Accepted by ApJ

References in corpus (9)

• Cold Dark Clouds: The Initial Conditions for Star Formation
• Density Fluctuations in MHD Turbulence: Spectra, Intermittency and Topology
• The Fractal Density Structure in Supersonic Isothermal Turbulence: Solenoidal versus Compressive Energy Injection
• The first Hi-GAL observations of the outer Galaxy: a look to star formation in the third Galactic quadrant in the longitude range 216.5 < l < 225.5
• Statistical properties of dust far-infrared emission
• Structure analysis of interstellar clouds: I. Improving the Delta-variance method
• Can We Trust the Dust? Evidence of Dust Segregation in Molecular Clouds
• Interstellar cloud structure: The statistics of centroid velocities
• A method for detection of structure

Cited by in corpus (16)

• Hi-GAL, the Herschel infrared Galactic Plane Survey: photometric maps and compact source catalogues. First data release for Inner Milky Way: +68°> l > -70°
• Properties of Hi-GAL clumps in the inner Galaxy]{The Hi-GAL compact source catalogue. I. The physical properties of the clumps in the inner Galaxy ($-71.0^{\circ }<\ell <67.0^{\circ }$)
• Star formation towards the Galactic HII region RCW120
• Multifractal Analysis of the Interstellar Medium. First application to Hi-GAL Observations
• Molecular cloud distances based on the MWISP CO survey and Gaia DR2
• A Morphological Classification of 18190 Molecular Clouds Identified in ${}^{12}$CO Data from the MWISP Survey
• The structure and characteristic scales of molecular clouds
• Galactic cold cores IX. Column density structures and radiative transfer modelling
• Modelling the structure of star clusters with fractional Brownian motion
• Description of turbulent dynamics in the interstellar medium: multifractal/microcanonical analysis I. Application to Herschel observations of the Musca filament
• Structure analysis of simulated molecular clouds with the Delta-variance
• The evolution of the internal structure of massive star forming regions in the Milky Way as revealed by ALMA
• Exposing the plural nature of molecular clouds : Extracting filaments and the CIB against the true scale-free interstellar medium
• Characterising lognormal fractional-Brownian-motion density fields with a Convolutional Neural Network
• A Deep Neural Network Approach to Compact Source Removal
• Cloud structure and young star distribution in the Dragonfish complex