New continuum observations of the Andromeda galaxy M 31 with FAST

分类： 物理学 >> 地球物理学、天文学和天体物理学 提交时间： 2023-09-20 合作期刊: 《Research in Astronomy and Astrophysics》

Wenjun Zhang Xiaohui Sun Jie Wang

摘要： We present a new total intensity image of M 31 at 1.248 GHz, observed with the Five-hundred-meter Aperture Spherical radio telescope (FAST) with an angular resolution of 4'' and a sensitivity of about 16 mK. The new FAST image clearly reveals weak emission outside the ring due to its high sensitivity on large-scale structures. We derive a scale length of 2.7 kpc for the cosmic ray electrons and find that the cosmic ray electrons propagate mainly through diffusion by comparing the scale length at 4.8 GHz. The spectral index of the total intensity varies along the ring, which can be attributed to the variation of the spectra of synchrotron emission. This variation is likely caused by the change of star formation rates along the ring. We find that the azimuthal profile of the non-thermal emission can be interpreted by an axisymmetric large-scale magnetic field with varying pitch angle along the ring, indicating a complicated magnetic field configuration in M 31.

通过

 点击量 139  下载量 62  评论