Molecular and infrared observations of the conical reflection nebula 1548C27

Abstract

We present 12CO |$J = 2-1$| and 3–2 and infrared observations of the region around the optical conical reflection nebula and jet source 1548C27. The CO data show that this source lies on the edge of a large molecular cloud. Wings of emission are evident in the higher transition, and the morphology indicates that this gas lies at the interface between the reflection nebula and the molecular cloud. A dynamical distance of 2.4 kpc is derived from the cloud velocity, indicating that the source is considerably more distant than previously thought. This implies a source mass and luminosity consistent with an Ae/Be-type star. The total mass of the high-velocity molecular gas is |$\approx 0.18 \enspace \text M_\odot$|⁠, making this a low-mass outflow; using the assumption of a canonical wind momentum driven flow, this gives a stellar mass-loss rate of |$\approx 1 \times 10^{-7} \enspace \text M_\odot \enspace \text {yr}^{-1}$|⁠. This source has thus both a highly collimated optical jet and uncollimated general molecular expansion into the ambient cloud. Our near-IR imaging photometry indicates that 1548C27 is variable over time-scales of a few years and is considerably redder than in the previous observation. The 70 × 70 arcsec2 field immediately surrounding the source contains 31 point-like sources, the majority of which appear to be reddened field stars rather than members of a young PMS cluster. Spectroscopy through the 8–13 µm window shows a continuum consistent with 350-K blackbody emission.