Spatially resolved H2 emission from a very low-mass star.

Context. Molecular outflows from very low-mass stars (VLMSs) and brown dwarfs have been studied very little. So far, only a few CO outflows have been observed, allowing us to map the immediate circumstellar environment. Aims. We present the first spatially resolved H2 emission around IRS54 (YLW52), a ~0.1-0.2 M☉ Class I source. Methods. By means of VLT SINFONI K-band observations, we probed the H2 emission down to the first ~50 AU from the source. Results. The molecular emission shows a complex structure delineating a large outflow cavity and an asymmetric molecular jet. Thanks to the detection of several H2 transitions, we are able to estimate average values along the jet-like structure (from source position to knot D) of AV ~ 28 mag, T ~ 2000-3000 K, and H2 column density N(H2) 1.7×1017 cm-2. This allows us to estimate a mass loss rate of ~2×10-10 M☉ yr-1 for the warm H2 component. In addition, from the total flux of the Br ʏ line, we infer an accretion luminosity and mass accretion rate of 0.64 L☉ and ~3 × 10-7 M☉ yr-1, respectively. The outflow structure is similar to those found in low-mass Class I and CTTS. However, the Lacc/Lbol ratio is very high (~80%), and the mass accretion rate is about one order of magnitude higher when compared to objects of roughly the same mass, pointing to the young nature of the investigated source. [ABSTRACT FROM AUTHOR]