In order to form a complete understanding of Star Formation, it is critical to determine the similarities and differences between low- and high-mass young stellar objects (YSOs) from both a physical and chemical perspective. Within this context, the "Water in Star forming regions with Herschel" key program (WISH; van Dishoeck et al. 2011) is investigating the different processes that characterise protostellar environments across a wide range of luminosities by observing water, CO and other important molecules. The study of the CO and isotopologue emission lines of 51 YSOs has shown a strong linear correlation between the line and bolometric luminosities for all observed lines, suggesting that high J CO transitions (J >= 5) can be used as tracers of dense gas. In addition, the majority of the 12CO line profiles can be decomposed into broad and narrow Gaussian components, while the C18O spectra show a single velocity component. Analysis of the C18O data has also motivated a more detailed study of the dynamics of protostellar envelopes. In these regions, non-thermal motions, such as turbulence and infall, dominate this line profile but in different amounts for low (J < 5) and high rotational transitions. The width of the C18O lines becomes broader at higher J for low-mass protostars but remains constant for more massive YSOs. For the first time a characterisation of the dynamics in the inner warmer regions of protostellar envelopes can be performed and compared to the colder outer parts as a function of source luminosity. This is achieved through comparison with 1-dimensional spherically symmetric radiative transfer models. This study will allow us to better understand where infall and turbulence are dominant within protostellar envelopes and how this varies with luminosity.
Protostars and Planets VI Posters
- Pub Date:
- July 2013