A case study of radio continuum emission tracing a proto-stellar jet from POETS

In the following, we show an example summarizing the information we can obtain by mapping in radio continuum (< 30 GHz) the environment of a young massive star. Continuum emission at these frequencies traces ionized hydrogen gas associated with material ejected from the young star, along the general direction of the system angular momentum. Depending on whether this material is more or less collimated, we talk about proto-stellar jets or winds, respectively. Thus, radio continuum emission can be used to study the geometry and energetics of the proto-stellar system.

Caption: prototypical example of radio continuum emission tracing a jet in the star-forming region G035.02+0.35.

The central panel shows a radio continuum map (in grey) over-plotted on an artistic conception of a proto-stellar jet (in cyan background). The radio continuum emission due to the jet is characterized by: (1) thermal free-free emission (≡ CM2) coincident with the position of the young star, and (2) a number of jet's knot (≡ CM3, CM4, CM6, CM7) along the route of the jet further away from the star. Continuum emission at the position of the jet's knot can be produced either by thermal bremsstrahlung or non-thermal synchrotron radiation, whose nature can be determined by the slope of the local spectral energy distribution (see side panels).
The side panels show the centimeter spectral energy distribution (spectral flux vs. frequency) of each radio continuum source between 5-22 GHz, whose spectral slope (α) tells us whether the emission is thermal or non-thermal in nature. This distinction depends on whether the value of α is greater or smaller than −0.1, respectively (where α is specified in the upper left corner of each panel above).

These observations were obtained with the VLA telescopes in New Mexico at 6 GHz achieving an angular resolution of 0.3 arcsec.

More details in, Sanna et al. 2019, A&A, 623, L3

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