摘要
We present high-resolution (∼0 .″ 05; 8 au) dust continuum and molecular line observations toward the Class I protostellar system IRAS 04169+2702 in the Taurus B213 region, as part of the Atacama Large Millimeter/submillimeter Array Large Program Early Planet Formation in Embedded Disks. The 1.3 mm dust continuum emission traces a circumstellar disk with a central depression toward the protostar. Our Karl G. Jansky Very Large Array observations of the same target reveal a single central peak dominated by free–free emission, which coincides with the depression of the thermal dust emission. The mean spectral index of the thermal dust emission from 1.3 mm to 1.4 cm is approximately 2.8, suggestive of the presence of grains grown to millimeter or centimeter sizes in the disk. Velocity gradients along the disk’s major axis are seen in emission from the 12CO (2–1), 13CO (2–1), and C18O (2–1) molecular lines. The position–velocity diagrams of these lines unveil a Keplerian-rotating disk with a radius of ∼21 au around a 1.3 M⊙ protostar, as well as an infalling and rotating envelope with the angular momentum conserved. In addition to the compact disk, large-scale infalling spiral structures extending up to approximately 1400 au, i.e., streamers, are discovered in C18O (2–1), SO (65–54), and H2CO (30,3–20,2) as well as in the 1.3 mm continuum emission. Notably, in the region closer to the protostar, the spatial coincidence of C18O and SO may indicate the presence of a shock related to accretion through the spiral arms.