JCMT BISTRO Survey observations of the Ophiuchus Molecular Cloud: Dust grain alignment properties inferred using a Ricean noise model

Abstract

The dependence of polarization fraction $p$ on total intensity $I$ in polarized submillimeter emission measurements is typically parameterized as $p\propto I^{-\alpha }$ $(\alpha \le 1)$, and used to infer dust grain alignment efficiency in star-forming regions, with an index $\alpha =1$ indicating near-total lack of alignment of grains with the magnetic field. In this work we demonstrate that the non-Gaussian noise characteristics of polarization fraction may produce apparent measurements of $\alpha \sim 1$ even in data with significant signal-to-noise in Stokes $Q$, $U$ and $I$ emission, and so with robust measurements of polarization angle. We present a simple model demonstrating this behavior, and propose a criterion by which well-characterized measurements of polarization fraction may be identified. We demonstrate that where our model is applicable, $\alpha$ can be recovered by fitting the $p-I$ relationship with the mean of the Rice distribution, without statistical debiasing of polarization fraction. We apply our model to JCMT BISTRO Survey POL-2 850$\mu$m observations of three clumps in the Ophiuchus Molecular Cloud, finding that in the externally-illuminated Oph A region, $\alpha \approx 0.34$, while in the more isolated Oph B and C, despite their differing star formation histories, $\alpha \sim 0.6-0.7$. Our results thus suggest that dust grain alignment in dense gas is more strongly influenced by incident interstellar radiation field than by star formation history. We further find that grains may remain aligned with the magnetic field at significantly higher gas densities than has previously been believed, thus allowing investigation of magnetic field properties within star-forming clumps and cores.

arXiv comment21 pages, 8 figures, 3 tables, accepted for publication in ApJ

References in corpus (38)

• Astropy: A Community Python Package for Astronomy
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• Radiative torques: Analytical Model and Basic Properties
• Planck intermediate results. XIX. An overview of the polarized thermal emission from Galactic dust
• SCUBA-2: iterative map-making with the Sub-Millimetre User Reduction Facility
• SCUBA-2: on-sky calibration using submillimetre standard sources
• Placing Confidence Limits on Polarization Measurements
• The Efficiency of Grain Alignment in Dense Interstellar Clouds: A Reassessment of Constraints from Near Infrared Polarization
• The JCMT Gould Belt Survey: First results from the SCUBA-2 observations of the Ophiuchus molecular cloud and a virial analysis of its prestellar core population
• Gaia-DR2 confirms VLBA parallaxes in Ophiuchus, Serpens and Aquila
• First results from BISTRO -- a SCUBA-2 polarimeter survey of the Gould Belt
• Is molecular gas necessary for star formation?
• First results from the Herschel Gould Belt Survey in Taurus
• On the radiation driven alignment of dust grains: Detection of the polarization hole in a starless core
• Interferometric Mapping of Magnetic Fields in Star-forming Regions II. NGC2024 FIR5
• Magnetic Fields in Star-Forming Molecular Clouds I. The First Polarimetry of OMC-3 in Orion A
• Grain Alignment in Starless Cores
• Magnetic fields towards Ophiuchus-B derived from SCUBA-2 polarization measurements
• A First Look at BISTRO Observations of The $\rho$ Oph-A core
• Radiative Torques on Interstellar Grains. III. Dynamics with Thermal Relaxation
• Polarization measurements analysis I. Impact of the full covariance matrix on polarization fraction and angle measurements
• JCMT BISTRO survey: Magnetic Fields within the Hub-Filament Structure in IC 5146
• The dust temperatures of the prestellar cores in the rho Oph main cloud and in other star forming regions: consequences for the core mass function
• The JCMT BISTRO Survey: The Magnetic Field of the Barnard 1 Star-Forming Region
• The JCMT BISTRO Survey: The Magnetic Field In The Starless Core $\rho$ Ophiuchus C
• Bayesian analysis of polarization measurements
• Condition for the formation of micron-sized dust grains in dense molecular cloud cores
• Polarization Properties and Magnetic Field Structures in the High-Mass Star-Forming Region W51 Observed with ALMA
• SILCC-Zoom: Polarisation and depolarisation in molecular clouds
• The JCMT and Herschel Gould Belt Surveys: A comparison of SCUBA-2 and Herschel data of dense cores in the Taurus dark cloud L1495
• Dust spectrum and polarisation at 850 um in the massive IRDC G035.39-00.33
• Comparing submillimeter polarized emission with near-infrared polarization of background stars for the Vela C molecular cloud
• A new polarisation amplitude bias reduction method
• Advanced Diagnostics for the Study of Linearly Polarized Emission. I: Derivation
• C^+ distribution around S1 in rho Ophiuchi
• Polarization of Thermal Emission from Aligned Dust Grains Under an Anisotropic Radiation Field
• Distortion of Magnetic Fields in a Starless Core V: Near-infrared and Submillimeter Polarization in FeSt 1-457
• A new method to suppress the bias in polarized intensity

Cited by in corpus (41)

• Magnetized filamentary gas flows feeding the young embedded cluster in Serpens South
• Dust polarized emission observations of NGC 6334; BISTRO reveals the details of the complex but organized magnetic field structure of the high-mass star-forming hub-filament network
• Zooming in on Individual Star Formation: Low- and High-mass Stars
• Grain alignment and disruption by radiative torques in dense molecular clouds and implication for polarization holes
• JCMT POL-2 and BISTRO Survey observations of magnetic fields in the L1689 molecular cloud
• Filament coalescence and hub structure in MonR2: Implications to massive star and cluster formation
• The far-infrared polarization spectrum of Rho Ophiuchi A from HAWC+/SOFIA observations
• 3D magnetic field morphology of the Perseus molecular cloud
• Magnetic Fields in Massive Star-Forming Regions (MagMaR) I. Linear Polarized Imaging of the UCHII Region G5.89-0.39
• B-fields in Star-Forming Region Observations (BISTRO): Magnetic Fields in the Filamentary Structures of Serpens Main
• Magnetic fields in the early stages of massive star formation as revealed by ALMA
• Revealing the diverse magnetic field morphologies in Taurus dense cores with sensitive sub-millimeter polarimetry
• The JCMT BISTRO survey: alignment between outflows and magnetic fields in dense cores/clumps
• The JCMT BISTRO Survey: A Spiral Magnetic Field in a Hub-filament Structure, Monoceros R2
• The role of the magnetic field in the fragmentation process: the case of G14.225-0.506
• Observations of magnetic fields surrounding LkH$\alpha$ 101 taken by the BISTRO survey with JCMT-POL-2
• SOFIA/HAWC+ Far-InfraRed Polarimetric Large Area CMZ Exploration (FIREPLACE) Survey I: General Results from the Pilot Program
• The JCMT BISTRO-2 Survey: Magnetic Fields of the Massive DR21 Filament
• JCMT BISTRO Observations: Magnetic Field Morphology of Bubbles Associated with NGC 6334
• Studying magnetic fields and dust in M17 using polarized thermal dust emission observed by SOFIA/HAWC+
• The JCMT BISTRO Survey: An 850/450$\mu$m Polarization Study of NGC 2071IR in OrionB
• SOFIA observations of 30 Doradus: I -- Far-Infrared dust polarization and implications for grain alignment and disruption by radiative torques
• Submillimetre observations of the two-component magnetic field in M82
• Polarised emission from aligned dust grains in nearby galaxies: predictions from the Auriga simulations
• Characterizing three-dimensional magnetic field, turbulence, and self-gravity in the star-forming region L1688
• The JCMT BISTRO Survey: Studying the Complex Magnetic Field of L43
• Atacama Large Aperture Submillimeter Telescope (AtLAST) Science: Our Galaxy
• 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 Fields and Fragmentation of Filaments in the Hub of California-X
• Distortion of Magnetic Fields in a Starless Core VI: Application of Flux Freezing Model and Core Formation of FeSt 1-457
• The JCMT BISTRO-2 Survey: The Magnetic Field in the Center of the Rosette Molecular Cloud
• Revealing the dust grain polarization properties as a function of extinction and distance towards NGC 1893
• Synthetic Modelling of Polarized Dust Emission in Intermediate-Mass YSOs: I: Constraining the Role of Iron Inclusions and Inelastic Relaxation on Grain Alignment with ALMA Polarization
• Alignment and Rotational Disruption of Dust Grains in the Galactic Centre Revealed by Polarized Dust Emission
• A Comparative Study of Dust Grain Polarisation Efficiencies in the Interstellar and Intracluster Mediums towards Anti-Center Galaxy
• The Formation of Filaments and Dense cores in the Cocoon Nebula (IC~5146)
• Near-Infrared Polarization from Unresolved Disks Around Brown Dwarfs and Young Stellar Objects
• The Rotation Dip in the Envelope-Disk Transition of HH 111: Evidence for Magnetic Braking
• The JCMT BISTRO Survey: The magnetised evolution of star-forming cores in the Ophiuchus Molecular Cloud interpreted using Histograms of Relative Orientation
• A Survey of Magnetic Field Properties in Bok Globules
• The role of radiative torques in the molecular cloud core L43