HAWC+ Far-infrared Observations of the Magnetic Field Geometry in M51 and NGC 891,The Astronomical Journal

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HAWC+ Far-infrared Observations of the Magnetic Field Geometry in M51 and NGC 891
The Astronomical Journal ( IF 5.1 ) Pub Date : 2020-09-21 , DOI: 10.3847/1538-3881/abada8
Terry Jay Jones ₁ , Jin-Ah Kim ₁ , C. Darren Dowell ₂ , Mark R. Morris ₃ , Jorge L. Pineda ₄ , Dominic J. Benford ₅ , Marc Berthoud _{6,

7} , David T. Chuss ₈ , Daniel A. Dale ₉ , L. M. Fissel ₁₀ , Paul F. Goldsmith ₂ , Ryan T. Hamilton ₁₁ , Shaul Hanany ₁₂ , Doyal A. Harper ₁₃ , Thomas K. Henning ₁₄ , Alex Lazarian ₁₅ , Leslie W. Looney ₁₆ , Joseph M. Michail _{7,

8,

17} , Giles Novak ₇ , Fabio P. Santos _{7,

18} , Kartik Sheth ₁₉ , Javad Siah ₈ , Gordon J. Stacey ₂₀ , Johannes Staguhn _{21,

22} , Ian W. Stephens ₂₃ , Konstantinos Tassis _{24,

25} , Christopher Q. Trinh ₂₆ , John E. Vaillancourt _{27,

28} , Derek Ward-Thompson ₂₉ , Michael Werner ₂ , Edward J. Wollack ₂₂ , Ellen G. Zweibel ₁₅

Affiliation

Minnesota Institute for Astrophysics, University of Minnesota, Minneapolis, MN 55455, USA
NASA Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
Department of Physics and Astronomy, University of California, Los Angeles, Box 951547, Los Angeles, CA 90095-1547, USA
Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
NASA Headquarters, 300 E Street SW, Washington, DC 20546, USA
Engineering + Technical Support Group, University of Chicago, Chicago, IL 60637, USA
Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), and Department of Physics & Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA
Department of Physics, Villanova University, 800 E Lancaster Avenue, Villanova, PA 19085, USA
Department of Physics & Astronomy, University of Wyoming, Laramie, WY, USA
Department of Physics, Engineering Physics and Astronomy, Queen's University, 64 Bader Lane, Kingston, ON K7L 3N6, Canada
Lowell Observatory, 1400 W Mars Hill Road, Flagstaff, AZ 86001, USA
School of Physics and Astronomy, University of Minnesota/Twin Cities, Minneapolis, MN 55455, USA
Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637, USA
Max Planck Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg, Germany
Department of Astronomy, University of Wisconsin, Madison, WI 53706, USA
Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801, USA
Department of Astrophysics and Planetary Science, Villanova University, 800 E Lancaster Avenue, Villanova, PA 19085, USA
Max-Planck-Institute for Astronomy, Knigstuhl 17, D-69117 Heidelberg, Germany
NASA Headquarters, 300 E Street SW, DC 20546, USA
Department of Astronomy, Cornell University, Ithaca, NY 14853, USA
Dept. of Physics & Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA
NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
Center for Astrophysics, Harvard & Smithsonian, 60 Garden Street, Cambridge, MA, USA
Department of Physics and ITCP, University of Crete, GR-70013 Heraklion, Greece
Institute of Astrophysics, Foundation for Research and Technology-Hellas, Vassilika Vouton, GR-70013 Heraklion, Greece
USRA/SOFIA, NASA Armstrong Flight Research Center, Building 703, Palmdale, CA 93550, USA
Universities Space Research Association, NASA Ames Research Center, Moffett Field, CA 94035, USA
Enrico Fermi Institute, Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637, USA
Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE, UK

Abstract: Stratospheric Observatory for Infrared Astronomy High-resolution Airborne Wideband Camera Plus polarimetry at 154 μm is reported for the face-on galaxy M51 and the edge-on galaxy NGC 891. For M51, the polarization vectors generally follow the spiral pattern defined by the molecular gas distribution, the far-infrared (FIR) intensity contours, and other tracers of star formation. The fractional polarization is much lower in the FIR-bright central regions than in the outer regions, and we rule out loss of grain alignment and variations in magnetic field strength as causes. When compared with existing synchrotron observations, which sample different regions with different weighting, we find the net position angles are strongly correlated, the fractional polarizations are moderately correlated, but the polarized intensities are uncorrelated. We argue that the low fractional polarization in the central regions must be due to significant numbers of highly turbulent segments across the beam and along lines of sight in the beam in the central 3 kpc of M51. For NGC 891, the FIR polarization vectors within an intensity contour of 1500 are oriented very close to the plane of the galaxy. The FIR polarimetry is probably sampling the magnetic field geometry in NGC 891 much deeper into the disk than is possible with NIR polarimetry and radio synchrotron measurements. In some locations in NGC 891, the FIR polarization is very low, suggesting we are preferentially viewing the magnetic field mostly along the line of sight, down the length of embedded spiral arms. There is tentative evidence for a vertical field in the polarized emission off the plane of the disk.

中文翻译：

M51 和 NGC 891 磁场几何的 HAWC+ 远红外观测

摘要：平流层红外天文台高分辨率机载宽带相机 Plus 偏振测量在 154 μm 上报道了正面星系 M51 和边缘星系 NGC 891。对于 M51，偏振矢量通常遵循由分子气体分布、远红外 (FIR) 强度等值线和其他恒星形成的示踪剂。FIR 明亮中心区域的部分极化比外部区域低得多，我们排除了晶粒排列损失和磁场强度变化的原因。与现有的同步加速器观测相比，对不同权重的不同区域进行采样，我们发现净位置角强相关，部分极化中等相关，但极化强度不相关。我们认为，中心区域的低分极化一定是由于在 M51 的中心 3 kpc 中穿过光束和沿着光束中的视线的大量高湍流段造成的。对于 NGC 891，强度等高线 1500 内的 FIR 偏振矢量非常接近星系平面。FIR 极化测量可能比 NIR 极化测量和无线电同步加速器测量更深地采样 NGC 891 中的磁场几何结构。在 NGC 891 的某些位置，远红外极化非常低，这表明我们主要沿着视线观察磁场，沿着嵌入的旋臂长度向下。有初步证据表明，在圆盘平面外的偏振发射中存在垂直场。

更新日期：2020-09-21

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