Astronomy and Astrophysics Seminars

A multi-scale, multi-wavelength study of massive star-forming region W42

by Dr. Lokesh Kumar Dewangan (National Institute for Astrophysics, Optics and Electronics (INAOE), Mexico)

Tuesday, July 28, 2015 from to (Asia/Kolkata)
at TIFR ( DAA Seminar A269 )
Description
In massive star formation research, it is extremely difficult to identify a promising 
sample of the precursors/early critical phases of O type massive stars. In the literature, 
there are only a handful of massive young stellar objects (MYSOs) known to be 
associated with highly collimated jets and/or Herbig-Haro (HH) objects.

I will present results of an analysis of massive star-forming region W42 using a 
multi-scale and multi-wavelength approach. These results throw light on the 
physical environment of W42 on smaller (about 5000 AU) and larger (about 10 pc) 
scales, helping to understand the formation and interaction of massive stars with 
their surrounding environment. A bipolar appearance of W42 complex (on scales of 
about 10 pc) is evident due to the ionizing feedback from the O5-O6 type star in a 
medium that is highly inhomogeneous. The VLT/NACO adaptive-optics K and 
Lp images resolved this ionizing source into multiple point-like sources 
below ~5000 AU scale. 

In this complex, we have discovered a parsec scale H2 outflow that is driven by an 
infrared counterpart of the 6.7-GHz methanol maser emission (i.e. W42-MME; stellar 
mass 19 solar mass and extinction 48 mag). Furthermore, we have investigated a 
collimated jet-like feature (in the inner 4500 AU) in W42-MME using the VLT NIR 
adaptive-optics images. The jet is located inside an envelope/cavity (extent ~10,640 AU) 
that is tapered at both ends and is oriented along the north-south direction. Such 
observed morphology of the outflow cavity around the massive star is scarcely known 
and is very crucial for understanding the jet-outflow formation process in massive star 
formation.