Through collaboration with the Max Planck Institute for Astronomy  (MPIA) in Heidelberg, a research team in the Purple Mountain Observatory  obtained the detailed optical view of the Vela C molecular cloud. They  have discovered 18 new Herbig-Haro objects (HHs) and 11 new extended  green objects (EGOs) by analyzing their optical images and archival  infrared images. The Vela C molecular cloud, as one of the nearest  massive star forming regions, is located at a distance of about 2300  light years away from Earth. The new outflows discovered in Vela C  confirm this region with active star formation.        

                  According to the low mass star  formation theory, stars are born in the molecular clouds. A giant  molecular cloud fragments into could cores due to gravity, turbulence,  and magnetic fields.  Protostars form at the centers of  dense cores. A young star accretes surrounding materials through its  circumstellar disk and, simultaneously, ejects materials to the  interstellar space. Mass outflow is the production of interaction  between the ejecta from young stars and the ambient interstellar medium.         

                 Outflows have been detected in  different wavelength: the Herbig-Haro objects, as the optical  manifestation of mass outflow, trace the material ejected by stars or  the shocked surrounding medium while the extended green objects, as the  mid-infrared outflows, trace the entrained surrounding medium with lower  temperature and density.        

                 Using the WFI instrument at the Max  Planck Gesellschaft (MPG) 2.2m telescope of the European Southern  Observatory (ESO) in Chile, the research team obtained a clear view of  HHs in the Vela C molecular cloud and finally identified 18 new HHs.  They also analyzed the archival infrared images from the Wide-field  Infrared Survey Explorer (WISE, details can be found in its official  website http://wise.ssl.berkeley.edu) and discovered 11 new EGOs. The  MPG telescope is built by Zeiss company and maintained by ESO. Through  collaboration with MPIA, the scientists in PMO obtained the observing  time of MPG telescope.  

  The  Vela C molecular cloud still stays at a very early stage of star  formation. Most of young stars in Vela C are embedded in large amounts  of gas and dust. Thus it’s hard to detect the young stars directly.  However, the outflows from the young stars can pierce the thick cloud  and be exposed to the astronomers. The investigation of outflows offers  the information of star formation in the Vela C molecular cloud. The  discovery of new outflows suggests that the Vela C molecular cloud is an  active star forming region. The research team also investigates the  possible driving sources of outflows and found 10 young stars with  outflows.  

By with for ZHANG Miaomiao

An example of outflow discovered in the Vela  C  molecular cloud. The left panel shows the [SII] narrow-band image of HH  1090. The right panel shows the false-color image of mid-infrared  counterpart of HH 1090. This color image is constructed with three WISE  images at different wavelength and the EGO exhibits as green color.    

                 The original paper is published in  Astronomical Journal: “Herbig-Haro objects and mid-infrared outflows in  the Vela C molecular cloud”    

(http://adsabs.harvard.edu/abs/2014AJ....148...26Z).