High-velocity ammonia emission associated with the young stellar object Serpens FIRS 1

Abstract

We have performed VLA, Haystack, and Effelsberg 100 m ammonia observations of the molecular core associated with the highly collimated radio continuum jet of the very young stellar object (YSO) Serpens FIRS 1. An analysis of the overall morphology, kinematics, and excitation of the ambient cloud core is presented. In particular, the mean rotational temperature derived over a region of 2' x 2' around FIRS 1 is found to be 12 K, whereas it increases to 30 K at distances within 6 '' from FIRS 1, indicating that FIRS 1 is the dominant energy source in the cloud core. By averaging the blueshifted (V-LSR = -6.1 --> +5.7 km s(-1)) and redshifted (V-LSR = +10.7 --> +22.5 km s(-1)) spectral channels of the VLA data with respect to the ambient cloud velocity (V-LSR = 7.0-9.4 km s(-1)), we have detected an excess of emission (above the expected continuum) that we identify as high-velocity ammonia emission associated with the YSO FIRS 1. The blue- and redshifted emissions seem to have a bipolar morphology, suggesting that they trace a bipolar ammonia outflow of similar to 20 '' in size and aligned with the radio continuum jet. We identify this high-velocity ammonia emission, with an estimated mass M(H-2) similar or equal to 0.2 [XNH(3)/10(-8))](-1) M., as associated with the molecular gas entrained by the radio jet. In addition, NH3 (1,1), (2,2), and (3,3) spectra of this region taken with the Haystack and the Effelsberg 100 m telescopes show ammonia emission at even higher velocities (up to similar to 30-40 km s(-1) from the line center) than those observed with the VLA (less than or similar to 20 km s(-1)), suggesting that the VLA observations cover only a fraction of the velocity range of the ammonia outflow. New VLA ammonia observations covering a higher velocity range are needed to fully map this high-velocity molecular emission and to confirm its bipolar distribution.