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HL Tau is a Class I-II protostar embedded in an infalling and rotatingenvelope and possibly associated with a planet forming disk, and it isco-located in a 0.1 pc molecular cloud with two nearby young stellar objects.Our ALMA observations revealed two arc-like structures on a 1000 au scaleconnected to the disk, and their kinematics could not be explained with anyconventional model of infalling and rotational motions. In this work, weinvestigate the nature of these arc-like structures connected to the HL Taudisk. We conducted new observations in the 13CO and C18O (3-2; 2-1) lines withJCMT and IRAM 30m, and obtained the ACA data with the 7-m array. With thesingle-dish, ACA, and ALMA data, we analyzed the gas motions on both 0.1 pc and1000 au scales in the HL Tau region. We constructed new kinematical models ofan infalling and rotating envelope with the consideration of relative motionbetween HL Tau and the envelope. By including the relative motion between HLTau and its protostellar envelope, our kinematical model can explain theobserved velocity features in the arc-like structures. The morphologies of thearc-like structures can also be explained with an asymmetric initial densitydistribution in our model envelope. In addition, our single-dish resultssupport that HL Tau is located at the edge of a large-scale (0.1 pc) expandingshell driven by the wind or outflow from XZ Tau, as suggested in theliterature. The estimated expanding velocity of the shell is comparable to therelative velocity between HL Tau and its envelope in our kinematical model.These results hints that the large-scale expanding motion likely impacts theprotostellar envelope around HL Tau and affects its gas kinematics. We foundthat the mass infalling rate from the envelope onto the HL Tau disk can bedecreased by a factor of two due to this impact by the large-scale expandingshell.

Signs of outflow feedback from a nearby young stellar object on the protostellar envelope around HL Tau