A multi-wavelength study of a double intermediate-mass protostar – from large-scale structure to collimated jets

Abstract

Aims. The earliest stages of intermediate- and high-mass star for mation remain poorly understood. To gain deeper insights, we study a previously discovered protostellar source that is deeply embedded and drives an energetic molecular outflow. Methods. The source, UYSO 1, located close to IRAS 07029‐1215 at a distance of about 1 kpc, was observed in the (sub)millimeter and centimeter wavelength ranges, as well as at near-, mid-, and far-infrared wavelengths. Results. The multi-wavelength observations resulted in the detection of a double intermediate-mass protostar at the location of UYSO 1. In addition to the associated molecular outflow, with a projected size of 0.25 pc, two intersecting near-infrared jets with projected sizes of 0.4 pc and 0.2 pc were found. However, no infrared counterparts to the driving sources could be detecte d in sensitive near- to far-infrared observations (including Spitzer ). In interferometric millimeter observations, UYSO 1 was resolved into two continuum sources with high column densities (> 10 24 cm −2 ) and gas masses of 3.5 M⊙ and 1.2 M⊙, with a linear separation of 4200 AU. We report the discovery of a H2O maser towards one of the two sources. Within an appropriate multi-wavelength coverage, the total luminosity is roughly estimated to be≈50 L⊙, shared by the two components, one of which is driving the molecular outflow that has a dynamical timescale of less than a few thous and years. The jets of the two individual components are not aligned. Submillimeter observations show that the region lacks the typical hot-core chemistry. Conclusions. We find two protostellar objects, whose associated circumst ellar and parent core masses are high enough to suggest that they may evolve into intermediate-mass stars. This is corroborated by their association with a very massive and energetic CO outflow, suggesting high protostellar accretion rates. The short dynamical timescale of the outflow, the pristine chemi cal composition of the cloud core and absence of hot core tracers, the absence of detectable radio continuum emission, and the very low protostellar luminosity argue for an extremely early evolutionary stage.