A search for radio jets from massive young stellar objects. Association
  of radio jets with H2O and CH3OH masers
  Recent theoretical and observational studies debate the similarities between
the formation process of high-mass (>8 Msun) and low-mass stars. The formation
of low-mass star formation is directly associated with the presence of disks
and jets. According to this scenario, radio jets are expected to be common in
high-mass star-forming regions. We aim to increase the number of known radio
jets in high-mass star forming regions by searching for radio jet candidates at
radio continuum wavelengths. We have used the Karl G. Jansky Very Large Array
(VLA) to observe 18 high-mass star-forming regions in the C band (6 cm, ~1.0
arcsec resolution) and K band (1.3 cm, ~0.3 arcsec resolution). We have
searched for radio jet candidates by studying the association of radio
continuum sources with shock activity signposts. We have identified 7 as the
most probable radio jets. The radio luminosity of the radio jet candidates is
correlated with the bolometric luminosity and the outflow momentum rate. About
7-36% of the radio jet candidates are associated with non-thermal emission. The
radio jet candidates associated with 6.7 GHz CH3OH maser emission are
preferentially thermal winds and jets, while a considerable fraction of radio
jet candidates associated with H2O masers show non-thermal emission, likely due
to strong shocks. Our sample of 18 regions is divided in 8 less evolved,
infrared-dark regions and 10 more evolved, infrared-bright regions. We have
found that ~71% of the identified radio jet candidates are located in the more
evolved regions. Similarly, 25% of the less evolved regions harbor one of the
most probable radio jets, while up to 50% of the more evolved regions contain
one of these radio jet candidates. This suggests that the detection of radio
jets in high-mass star forming regions is larger in slightly more evolved
regions.
