SF-01-0009

Revealing the Multi-Component Magnetic Field along the Line-of-Sight with Optical Polarimetry

Yasuo Doi, Koji S. Kawabata, Masafumi Matsumura, Hiroshi Akitaya, Simon Coude, Claudia Vilega Rodrigues, Pierre Bastien, Mehrnoosh Tahani, Sarah Sadavoy, Shu-ichiro Inutsuka, Tetsuo Hasegawa

We combined optical polarimetry data with published Gaia stellar distances to probe the magnetic field structure along the line-of-sight toward the Perseus molecular cloud complex. We found that the magnetic field associated with the Perseus molecular cloud at a distance of about 300 pc has a mean polarization position angle of -37 degrees East of North. We also identified a foreground dust cloud at 150 pc in the same direction, which we found is the outer edge of the Taurus molecular cloud. The mean magnetic field position angle of this foreground cloud is +67 degrees. We also analyzed Gaia's interstellar extinction data in the Taurus-Perseus field and identified a low-density elliptical-shaped dust cavity at l = 170 deg, b = -20 deg, and d = 240 pc with a diameter of 100-160 pc. The observed polarization position angles are expected to be tracing the plane-of-sky orientations of the magnetic field at the front and at the back of this dust cavity. In addition, we extended this tomographic imaging technique through optical polarimetry in the direction of the Sagittarius Galactic arm. We found that the position angle of the magnetic field in the arm varies significantly at three distances along the line-of-sight (i.e., 174, 87, and 157 degrees at 1.57, 1.71, and 2.36 kpc, respectively). We use this information to successfully extract the intrinsic plane-of-sky magnetic field structure associated with each cloud. The column density of probed clouds is 1?4x10^21 cm-2, and the magnetic field of each cloud is relatively ordered at ~5-10 pc scales. We estimate their turbulent magnetic field amplitude, corresponding to the magnetic field intensity of ~17 ? 220 uG.