Protostar L1455 IRS1: Rotating Disk Connecting to Filamentary Network

Abstract

We conducted IRAM-30m C18O (2-1) and SMA 1.3mm continuum, 12CO (2-1), and C18O (2-1) observations toward the Class 0/I protostar L1455 IRS1 in Perseus. The IRAM results show L1455 IRS1 located in a dense core of 0.05 pc in size with a mass of 0.54M_sun, connecting to a filamentary structure. Inside the dense core, compact components of 350 AU and 1500 AU are detected in the SMA 1.3 mm continuum and C18O, with a velocity gradient in the latter one perpendicular to a bipolar outflow in 12CO, likely tracing a rotational motion. We measure a rotational velocity profile ~ r^-0.75 that becomes shallower at a turning radius of ~200 AU which is approximately 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 0.28 M_sun. We derive a core rotation that is about one order of magnitude faster than expected. A significant velocity gradient along a filament towards IRS1 indicates that this filament is dynamically important, providing a gas reservoir and possibly responsible for the faster-than-average core rotation. Previous polarimetric observations show a magnetic field aligned with the outflow axis and perpendicular to the associated filament on a 0.1~pc scale, while on the inner 1000 AU scale, the field becomes perpendicular to the outflow axis.This change in magnetic field orientations is consistent with our estimated increase in rotational energy from large to small scales that overcomes the magnetic field energy, wrapping the field lines and aligning them with the disk velocity gradient. These results are discussed in the context of the interplay between filament, magnetic field, and gas kinematics from large to small scale. Possible emerging trends are explored with a sample of 8 Class 0/I protostars.