Surveying Magnetic Field with Velocity Gradient Technique in - PowerPoint PPT Presentation

Surveying Magnetic Field with Velocity Gradient Technique in Molecular Clouds Speaker：Yue Hu Date：2/11/2018

1. Introduction 2. Morphology of Magnetic Field CONTENT 3. Magnetization Level 4. Prediction for Smith Cloud

1. Introduction The dynamics of the ISM E mag Magnetic Field ≈ Turbulence E tur >> Gravity E grav

1. Introduction The role of the magnetic field in ISM Galaxy Molecular The magnetic field regulates the Cloud formation and evolution of both large and small scale structures Galaxies ~100,000 light years Molecular Clouds ~100 light years Protostar Dense Cores Dense Cores ~ light years Protostar ~ light hours

1. Introduction The approach to study the magnetic field Planck collaboration (2014) Planck collaboration (2015) Crutcher et al. (2010) Oppermann et al. (2012) Dust Synchrotron Zeeman Faraday Polarization Emission Splitting Rotation Available in dusty ISM Available in CR-filled ISM Available in neutral region Available in ionized region Orientation of Orientation and Strength of Strength and sign of Strength and sign of B B B B  // // 

1. Introduction Limitation of polarization Planck ALMA Credits: Brandon Hensley Instrument Billion Insufficient complexity dollars cost polarization percentage

1. Introduction The Velocity Gradients Technique B-field Gradients mean B - field direction K. H. Yuen and A. Turbulent eddies Lazarian. ApJ, 837:24, 2017. Gradient Gradient Smaller scale = more anisotropic

2. Tracing The Morphology of the Magnetic Field Observational Data on Molecular Clouds Taurus ( 13 CO) Quabbin millimeter wave telescope Smith Cloud Green Bank telescope Perseus ( 13 CO) (H I data) FCRAO telescope NGC 1333 ( 13 CO) Serpens ( 13 CO) L 1551 ( 13 CO) Heinrich Hertz Heinrich Hertz Nobeyama Radio Observatory Submillimeter Submillimeter telescope 45m telescope telescope

2. Tracing The Morphology of the Magnetic Field Agreement with Planck Polarization (353GHz) Taurus 13 CO Taurus Planck Velocity Gradients Technique Planck Dust Polarization

2. Tracing The Morphology of the Magnetic Field Agreement with Planck Polarization (353GHz) Serpens NGC 1333 1      2 AM 2 ( cos ) 2 θ is the relative angle between gradients and Planck polarization Cloud Region Emission Line AM Taurus 13 CO: J=1-0 0.75 L 1551 Perseus A 13 CO: J=1-0 0.70 Serpens 13 CO: J=1-0 0.78 NGC 1333 13 CO: J=2-1 0.77 L 1551 13 CO: J=2-1 0.82 AM = -1 0 AM=1 parallel perpendicular

2. Tracing The Morphology of the Magnetic Field Prediction for Smith Cloud Smith Cloud Smith Cloud : a high-velocity diffuse H I cloud, with no detected dust, the morphology of the magnetic field cannot 请输入标题 be investigated using dust polarimetry. Saxton/Lockman/NRAO/AUI/NSF/Mellinger

3. Magnetization Level Correlation between VGs and M A Orientation of VGs Orientation of VGs Bins Bins Low M A High M A Angle Angle Weak Strong less dispersed More dispersed B-field B-field     M 0 . 14 ( 1 R ) 0 . 09 , M 1 Lazarian et al 2018 A A     M 0 . 06 ( 1 R ) 0 . 09 , M 1 power law A A         2 2 R cos sin

3. Magnetization Level Magnetization Distribution Magnetization (M A-1 ) bowtie mark 0.50 0.75 1.00 1.25 T A* [K km/s] 25 29 ° 20 15 27 ° Dec . 10 1. Direction: gradients 25 ° Taurus 2. Color: magnetization 5 13 CO J = 1-0 3. Angle Δθ : uncertainty AM=0.75 Quabbin millimeter-wave telescope 0 23 °

3. Magnetization Level Agreement with Planck Polarization (353GHz) Serpens NGC 1333 L 1551 Cloud M A (Pol) M A (VGT) Taurus 1.11 1.18 Perseus A 1.20 1.14 Serpens 0.76 0.89 NGC 1333 0.95 0.83 L 1551 0.67 0.79

4. Prediction of Smith Cloud Prediction for Smith Cloud Smith Cloud Smith Cloud : a high-velocity diffuse H I cloud, with no detected dust, the morphology of the magnetic field cannot 请输入标题 be investigated using dust polarimetry. B // ≥ 3μG, consistent with the estimate of Hill et al (2013) Saxton/Lockman/NRAO/AUI/NSF/Mellinger

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