Protostars and Outflows in the NGC 7538 - IRS 9 Cloud Core

New high resolution observations of HCO J=1→0, HCN J=1→0, SO 22 → 11, and continuum with BIMA at 3.4 mm show that the NGC7538 IRS 9 cloud core is a site of active ongoing star formation. Our observations reveal at least three young bipolar molecular outflows, all ∼ 10,000 – 20,000 years old. IRS 9 drives a bipolar, extreme high velocity outflow observed nearly pole on. South of IRS 9 we find a cold, protostellar condensation with a size of ∼ 14 × 6 with a mass > 250 M⊙. This is the center of one of the outflows and shows deep, red-shifted self absorption in HCO, suggesting that there is a protostar embedded in the core, still in a phase of active accretion. This source is not detected in the far infrared, suggesting that the luminosity < 10 L⊙; yet the mass of the outflow is ∼ 60 M⊙. The red-shifted HCO + self-absorption profiles observed toward the southern protostar and IRS 9 predict accretion rates of a few times 10 to 10 M⊙ yr . Deep VLA continuum observations at 3.6 cm show that IRS 9 coincides with a faint thermal VLA source, but no other young star in the IRS 9 region has any detectable free-free emission at a level of ∼ 60 μJy at 3.6 cm. The HCO abundance is significantly enhanced in the hot IRS 9 outflow. A direct comparison of mass estimates from HCO and CO for the well-characterized red-shifted IRS 9 outflow predicts an HCO enhancement of more than a factor of 30, or [HCO/H2] ≥ 6 10 . Subject headings: ISM: clouds – ISM: molecules – radio lines – ISM:masers – ISM: individual – NGC7538 IRS 9 (stars:) circumstellar matter – stars: formation – stars: pre-main sequence SOFIA-USRA, NASA Ames Research Center, MS N211-3, Moffett Field, CA 94035, U.S.A. National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801, U.S.A. Radio Astronomy Laboratory, University of California, Berkeley 601 Campbell Hall, Berkeley, CA 94720, U.S.A.