Are Large, Cometary-Shaped Proplyds really (free-floating) EGGs?

Abstract

We report the detection of strong and compact molecular line emission (in the CO J=3-2, 4-3, 6-5, 7-6, 13CO J=3-2, HCN and HCO+ J=4-3 transitions) from a cometary-shaped object (Carina-frEGG1) in the Carina star-forming region (SFR) previously classified as a photoevaporating protoplanetary disk (proplyd). We derive a molecular mass of 0.35 Msun for Carina-frEGG1, which shows that it is not a proplyd, but belongs to a class of free-floating evaporating gas globules (frEGGs) recently found in the Cygnus SFR by Sahai, Morris & Claussen (2012). Archival Adaptive Optics near-IR (Ks) images show a central hourglass-shaped nebula. The derived source luminosity (about 8-18 Lsun), the hourglass morphology, and the presence of collimated jets seen in HST images, imply the presence of a jet-driving, young, low-mass star deeply embedded in the dust inside Carina-frEGG1. Our results suggest that the true nature of many or most such cometary-shaped objects seen in massive SFRs and previously labelled as proplyds has been misunderstood, and that these are really frEGGs.