Hsuan-Gu Chou1,2*, Hsi-Wei Yen1, Patrick M. Koch1
1Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan
2Department of Physics, National Taiwan University, Taipei, Taiwan
* presenting author:Hsuan-Gu Chou,
We have conducted IRAM-30m C18O (2–1) and SMA 1.3 mm continuum, 12CO (2–1), and C18O (2–1) observations toward the Class 0-I protostar L1455 IRS1. The IRAM-30m C18O results show L1455 IRS1 located in a dense core of 0.05pc in size with a mass of 0.35 M_sun. Besides, we identify a filamentary structure connecting to the dense core. This filament exhibits a velocity gradient of ~8.1 km s-1 pc along its longitudinal axis, leading to a mass flow rate of ~1.9 M_sun Myr-1. Inside the dense core, compact components with sizes of ~1.4" (350 AU) and ~6" (1500 AU) are detected in the SMA 1.3 mm continuum and C18O emission, respectively. The C18O component shows signatures of spin-up rotation. The radial profile of the rotational velocity is measured to be proportional to r^-0.75, and the specific angular momentum on a 500 AU scale is estimated to be 1.0 × 10^-3 km s-1 pc. The rotational profile becomes shallower at a radius of ~200 AU. This turning point is approximately at the radius of the 1.3 mm continuum component. These results hint the presence of a Keplerian disk with a radius <200 AU around L1455 IRS1 with a protostellar mass of about 0.2 M_sun. Previous polarimetric observations of L1455 IRS1 have shown that on a 0.1 pc scale, the orientation of the magnetic field is aligned with the outflow axis and perpendicular to the associated filament, while on the inner 1000 AU scale, the field becomes perpendicular to the outflow axis. The faster envelope rotation seen in L1455 IRS1 could be related to the feeding from the associated filament, and the change in the orientation of the magnetic field could be due to the increasing rotational energy from large to small scales. These results are discussed in the context of the interplay between filament, magnetic field, and gas kinematics. This work is submitted to the Astrophysical Journal.

Keywords: star formation, protoplanetary disk, filamentary kinematics, magnetic fields