The geometry of the magnetic field in the central molecular zone measured by PILOT
The geometry of the magnetic field in the central molecular zone measured by PILOT
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DOI：
10.1051/0004-6361/201935072
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发表时间：
2019-01
影响因子：
6.5
通讯作者：
A. Mangilli;J. Aumont;J. Bernard;A. Buzzelli;G. Gasperis;J. Durrive;K. Ferrière;G. Foënard;A. Hughes;A. Lacourt;R. Misawa;L. Montier;B. Mot;I. Ristorcelli;H. Roussel;P. Ade;D. Alina;P. Bernardis;E. Pino;Jean-Pierre Dubois;C. Engel;V. Guillet;P. Hargrave;R. Laureijs;Y. Longval;B. Maffei;A. M. Magalhes;C. Marty;S. Masi;J. Montel;F. Pajot;E. Perot;L. Rodriguez;M. Salatino;M. Saccoccio;G. Savini;S. Stever;J. Tauber;C. Tibbs;C. Tucker
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作者：
A. Mangilli;J. Aumont;J. Bernard;A. Buzzelli;G. Gasperis;J. Durrive;K. Ferrière;G. Foënard;A. Hughes;A. Lacourt;R. Misawa;L. Montier;B. Mot;I. Ristorcelli;H. Roussel;P. Ade;D. Alina;P. Bernardis;E. Pino;Jean-Pierre Dubois;C. Engel;V. Guillet;P. Hargrave;R. Laureijs;Y. Longval;B. Maffei;A. M. Magalhes;C. Marty;S. Masi;J. Montel;F. Pajot;E. Perot;L. Rodriguez;M. Salatino;M. Saccoccio;G. Savini;S. Stever;J. Tauber;C. Tibbs;C. Tucker
我们提出了第一个远红外（FIR）尘埃发射偏振图，涵盖了整个银河系的中央分子区（CMZ）。PILOT气球实验获得的数据覆盖了银河系中心区域− 2° <b < 2°，− 4° < B < 3°，波长为240 μm，角分辨率为2.2′。从我们测量的尘埃偏振角，我们推断出投射到天空平面（POS）上的磁场方向在CMZ的整个范围内都是非常有序的，相对于银河平面顺时针方向的平均倾斜角为1.22 °。我们的研究结果证实了以前的说法，跟踪尘埃偏振发射的字段是定向的GHz的无线电同步辐射跟踪在银河系中心区域的字段几乎正交。所观察到的场结构与353和217 GHz的最新普朗克极化数据在全球范围内是兼容的。在我们的数据中减去扩展发射后，我们得到的平均场取向与JCMT在20和50 km s−1分子云中以更高的角分辨率测量的平均场取向吻合得很好。我们发现没有证据表明，磁场方向是有关的100 pc的扭曲环结构内的CMZ。普朗克在353 GHz测量的银河系中心区域的低极化率结合高度有序的投影场方向是不寻常的。这个特征实际上延伸到整个银河系内平面。我们认为，这可能是由于朝向银河系内部平面的长视线造成的湍流细胞数量增加，或者是由于银河系内部区域特有的尘埃特性造成的。假设磁压力和冲压压力之间均分，我们得到的几个CMZ分子云的磁场强度估计的顺序为1 mG。
We present the first far infrared (FIR) dust emission polarization map covering the full extent of Milky Way’s central molecular zone (CMZ). The data, obtained with the PILOT balloon-borne experiment, covers the Galactic center region − 2° < ℓ < 2°, − 4° < b < 3° at a wavelength of 240 μm and an angular resolution of 2.2′. From our measured dust polarization angles, we infer a magnetic field orientation projected onto the plane of the sky (POS) that is remarkably ordered over the full extent of the CMZ, with an average tilt angle of ≃22° clockwise with respect to the Galactic plane. Our results confirm previous claims that the field traced by dust polarized emission is oriented nearly orthogonally to the field traced by GHz radio synchrotron emission in the Galactic center region. The observed field structure is globally compatible with the latest Planck polarization data at 353 and 217 GHz. Upon subtraction of the extended emission in our data, the mean field orientation that we obtain shows good agreement with the mean field orientation measured at higher angular resolution by the JCMT within the 20 and 50 km s−1 molecular clouds. We find no evidence that the magnetic field orientation is related to the 100 pc twisted ring structure within the CMZ. The low polarization fraction in the Galactic center region measured with Planck at 353 GHz combined with a highly ordered projected field orientation is unusual. This feature actually extends to the whole inner Galactic plane. We propose that it could be caused by the increased number of turbulent cells for the long lines of sight towards the inner Galactic plane or to dust properties specific to the inner regions of the Galaxy. Assuming equipartition between magnetic pressure and ram pressure, we obtain magnetic field strength estimates of the order of 1 mG for several CMZ molecular clouds.