A Remarkable Bipolar Flow in the Center of the Rho Ophiuchi Cloud

Abstract

Using the IRAM 30-m telescope in August and December 1988, we have discovered the first molecular outflow in the central part (L1688) of the nearby ρ Ophiuchi dark cloud. This outflow, found in the J = 2 — 1 line of 12CO near the cloud core A, is an extreme case, weak (outflow mass-loss rate ≈ 5 x 10−8M⊙yr−1) and highly collimated (lenght to width ratio > 14), which explains why it has escaped previous detections with smaller telescopes. The high-velocity molecular gas is hot and optically thin, making the J = 2 — 1 line of 12CO ≈ 3-4 times stronger than the J = 1 — 0 line. Unexpectedly, this outflow does not appears to be driven by any of the embedded near-IR sources known in this region previous deep VLA surveys of the cloud (André, Montmerle, and Feigelson, 1987; Stine et al., 1988; André et al., in prep.). The outflow exciting source is thus probably a very low-luminosity ((L < 0.1L⊙) young stellar object. Using the 30-m equipped with the MPIfIR bolometer, we have very recently found (March 1989) that this object is the strongest continuum point source of L1688 at 1.3 mm. By analogy with L1551-IRS5 and HL Tau, the radio properties of this source suggest that it possesses a weak, possibly collimated, ionized wind and a relatively massive, cold circumstellar disk (Mdisk ≈0.1M⊙).