Limitations of the modified blackbody fit method for determining molecular cloud properties

Abstract

Achieving a comprehensive understanding of the star and planet formation process is one of the fundamental tasks of astrophysics, requiring detailed knowledge of the physical conditions during the different phases of this process. During the earliest stages, i.e., concerning physical processes in molecular clouds and filaments, the column density N(H2), dust temperature T and dust emissivity index \b{eta} of these objects can be derived by adopting a modified blackbody fit of the far-infrared to (sub-)millimeter spectral energy distributions. However, this often applied method is based on various assumptions. In addition, the observational basis and required, but only assumed cloud properties, such as a limited wavelength-coverage of the spectral energy distribution and dust properties, respectively, may differ between different studies. We review the basic limitations of this method and evaluate their impact on the derived physical properties of the objects of interest, i.e., molecular clouds and filaments. We find that the highest uncertainty when applying this method is introduced by the often poorly constrained dust properties. Therefore, we propose to first derive the optical depth and subsequently the column density with the help of a suitable dust model as the optical depth can be obtained with high accuracy, especially at longer wavelengths. The method provides reliable results up to the high densities and corresponding optical depths observed in molecular clouds. Considering typically used observational data, i.e., measurements obtained with far-infrared instruments like Herschel/PACS, JCMT/SCUBA-2 and SOFIA/HAWC+, data at four wavelengths are sufficient to obtain accurate results. Furthermore, we find that the dust emissivity index \b{eta} derived with this method is not suitable as an indicator of dust grain size.

arXiv commentAccepted for publication in Astronomische Nachrichten, 19 pages, 12 figures

References in corpus (70)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Herschel Space Observatory - An ESA facility for far-infrared and submillimetre astronomy
• Dust Grain Size Distributions and Extinction in the Milky Way, LMC, and SMC
• The Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory
• The Herschel-SPIRE instrument and its in-flight performance
• Planck 2013 results. XI. All-sky model of thermal dust emission
• On the Submillimeter Opacity of Protoplanetary Disks
• Scattering by Interstellar Dust Grains. II. X-Rays
• Tracing Magnetic Fields with Aligned Grains
• The Aquila prestellar core population revealed by Herschel
• SCUBA-2: on-sky calibration using submillimetre standard sources
• SCUBA Polarization Measurements of the Magnetic Field Strengths in the L183, L1544, and L43 Prestellar Cores
• The Gould's Belt Distances Survey (GOBELINS) II. Distances and structure towards the Orion Molecular Clouds
• The Effect of Line of Sight Temperature Variation and Noise on Dust Continuum Observations
• Planck Early Results XXIV: Dust in the diffuse interstellar medium and the Galactic halo
• Inverse temperature dependence of the dust submillimeter spectral index
• A census of dense cores in the Aquila cloud complex: SPIRE/PACS observations from the Herschel Gould Belt survey
• Radiative transfer with POLARIS: I. Analysis of magnetic fields through synthetic dust continuum polarization measurements
• Polarized Far-Infrared and Submillimeter Emission from Interstellar Dust
• The Circumstellar Disk of the Butterfly Star in Taurus
• Investigating planet formation in circumstellar disks: CARMA observations of RY Tau and DG Tau
• The Effect of Noise on the Dust Temperature - Spectral Index Correlation
• The Herschel and JCMT Gould Belt Surveys: Constraining Dust Properties in the Perseus B1 Clump with PACS, SPIRE, and SCUBA-2
• The Dust Properties of Bubble HII Regions as seen by Herschel
• Balloon-Borne Submillimeter Polarimetry of the Vela C Molecular Cloud: Systematic Dependence of Polarization Fraction on Column Density and Local Polarization-Angle Dispersion
• Dust in the diffuse interstellar medium: Extinction, emission, linear and circular polarisation
• HAWC+/SOFIA Multiwavelength Polarimetric Observations of OMC-1
• Turbulence and star formation efficiency in molecular clouds: solenoidal versus compressive motions in Orion B
• Dust models compatible with Planck intensity and polarization data in translucent lines of sight
• Modeling the Physical Structure of the Low Density Pre-protostellar Core Lynds 1498
• Using Herschel and Planck observations to delineate the role of magnetic fields in molecular cloud structure
• Low dust emissivities and radial variations in the envelopes of Class 0 protostars: a signature of early grain growth?
• The Dielectric Function of "Astrodust" and Predictions for Polarization in the 3.4$\mu$m and 10$\mu$m Features
• Magnetic field evolution in Bok globules
• Interferometric multi-wavelength (sub)millimeter continuum study of the young high-mass protocluster IRAS05358+3543
• A Tale of Planet Formation: From Dust to Planets
• A First Look at BISTRO Observations of The $\rho$ Oph-A core
• The circumstellar disc in the Bok globule CB 26: Multi-wavelength observations and modelling of the dust disc and envelope
• A $Herschel-SPIRE$ Survey of the Mon R2 Giant Molecular Cloud: Analysis of the Gas Column Density Probability Density Function
• SCUBA polarisation observations of the magnetic fields in the prestellar cores L1498 and L1517B
• Indirect evidence of significant grain growth in young protostellar envelopes from polarized dust emission
• Physical Model of Dust Polarization by Radiative Torque Alignment and Disruption and Implications for Grain Internal Structures
• The far-infrared polarization spectrum of Rho Ophiuchi A from HAWC+/SOFIA observations
• Cloud structure of three Galactic infrared dark star-forming regions from combining ground and space based bolometric observations
• Grain size limits derived from 3.6 μm and 4.5 μm coreshine
• A statistical analysis of dust polarization properties in ALMA observations of Class 0 protostellar cores
• Understanding the origin of the magnetic field morphology in the wide-binary protostellar system BHR 71
• Submillimeter Polarization Spectrum in the Vela C Molecular Cloud
• Submillimeter mapping and analysis of cold dust condensations in the Orion M42 star forming complex
• The Millimeter Continuum Size-Frequency Relationship in the UZ Tau E Disk
• Tracing the ISM magnetic field morphology: The potential of multi-wavelength polarization measurements
• The census of dense cores in the Serpens region from the Herschel Gould Belt Survey
• Magnetically regulated disk-formation in the inner 100 au region of the Class 0 young stellar object OMC-3/MMS~6 resolved by JVLA and ALMA
• Submillimeter dust emission of the M17 complex measured with PRONAOS
• Interstellar extinction and polarization -- A spheroidal dust grain approach perspective
• Spectral energy distribution modelling of Southern candidate massive protostars using the Bayesian inference method
• Coreshine in L1506C - Evidence for a primitive big-grain component or indication for a turbulent core history?
• Galactic Cold Cores. VIII. Filament formation and evolution: Filament properties in context with evolutionary models
• Constraining the magnetic field properties of Bok globule B335 using SOFIA/HAWC+
• Interferometric study on the temporal variability of the brightness distributions of protoplanetary disks
• Self-scattering in protoplanetary disks with dust settling
• The role of turbulence, magnetic fields and feedback for star formation
• Fourier Transform Spectroscopy of the submillimetre continuum emission from hot molecular cores
• The JCMT BISTRO Survey: Multi-wavelength polarimetry of bright regions in NGC 2071 in the far-infrared/submillimetre range, with POL-2 and HAWC+
• Magnetic field structure of OMC-3 in the far infrared revealed by SOFIA/HAWC+
• Dust Models for the Extinction of Type IIn Supernova SN 2010jl
• Infrared study of the star-forming region associated with the UC HII regions G45.07+0.13 and G45.12+0.13
• SOFIA/HAWC+ observations of the Crab Nebula: dust properties from polarised emission
• Galatic HII region IRAS 17149$-$3916 -- A multiwavelength study
• Spitzer and Herschel studies of dust in supernova remnants in the Small Magellanic Cloud

Cited by in corpus (1)

• The role of radiative torques in the molecular cloud core L43