EPoS Contribution
EPoS Contribution
Deep Radio Continuum Observations of Massive Protostars: A Search for Jets

Viviana Rosero
NMT, Socorro, New Mexico, US
Molecular outflows appear to be an ubiquitous phenomena among stars of all masses. However, to date only a handful of sources with disks and collimated jets have been detected in young massive objects (YMOs). It is not clear if the lack of detections are due to intrinsic properties of YMOs or due to observational disadvantages. We have performed a survey of YMOs with unprecedented sensitivity, using the Jansky VLA to achieve ~3-10 microJy RMS in C and K-band images (about 10-100 times more sensitive than previous efforts). The sample is composed of the earliest stages of massive star formation: hot molecular cores and cold molecular cores. Moreover, all the sources show signatures of massive star formation such as methanol and water masers and outflow phenomena. This study provides a sample of jet candidates which is a valuable basis for a follow up search for associated disks. In this contribution, we present sub-arcsecond resolution continuum observations of ~ 30 star forming regions from our survey. We have a high detection rate of weak radio continuum emission from the YMOs in our sample (see figure), most of which were previously undetected. We have measured their spectral behavior and we are in the process of investigating their physical nature. In addition to the jet scenario, we are analyzing which other processes could be producing the radio emission; some of the detections appear to be from non-thermal emission, and others could be associated with ultra-compact HII regions. Before the upgrade of the VLA, most of the HII regions detected were B0 type stars (or earlier). Hence, these highly sensitive sample of YSOs open a new door of results, from HII regions associated with late B-type stars to very weak, collimated ionized jets associated to very early YMOs. Results from a specific example, the detection towards the G11.11-0.12P1 star forming region, are also presented.
Caption: Examples of sources that show a string of radio components and a morphology which could be potentially of jet nature.
Collaborators:
P. Hofner, NMT, USA
S. Kurtz, CRyA-UNAM, Mexico
R. Cesaroni, INAF, Italy
C. Carrasco, CRyA-UNAM, Mexico
L. Rodriguez, CRyA-UNAM, Mexico
K. Menten, MPIfR, Germany
F. Wyrowski, MPIfR, Germany
E. Araya, WIU, USA
L. Loinard, CRyA-UNAM, Mexico
S. Ellingsen, UTAS, Australia
Suggested Session: Protostellar Outflows