Searching for the driving source of the CO molecular outflow in the high-mass star-forming region G240.31+0.07.
Abstract (from CDS):
We present low and high angular resolution observations at 1.3, 3.6, and 6 cm obtained from the Very Large Array archive toward the high-mass star formation region G240.31+0.07. We detected, at least, two continuum sources toward G240.31+0.07 at 1.3 cm, which are spatially associated with the millimeter sources MM1 and MM3 reported in the region. Two continuum sources are also detected in the region at 3.6 and 6 cm, spatially coinciding with the millimeter sources MM1 and MM2. We find that the sources MM2 and MM3 seem to be consistent with ultracompact H II regions, harboring B1-0.5 spectral-type zero-age main-sequence stars. Based on the flux density at 1.3, 3.6, and 6 cm, we also find that the spectral index of MM1 is about -0.4, suggesting a combination of thermal and nonthermal emission. In order to search the nature of MM1, we present a detailed comparison of the high angular resolution 6 cm observations of the epochs 1990.3 and 1995.5. The difference image of the two epochs shows variability toward MM1; its flux density and morphology are changing with time. Moreover, a condensation, possibly ejected by MM1 and oriented in the same direction of the CO outflow observed in the region, is also detected. We propose that MM1 is a radio jet and the best candidate to be the driving source of the CO outflow observed in the region.