Person:

Pineda, Jaime

We present (NH_3) observations of the B5 region in Perseus obtained with the Green Bank Telescope. The map covers a region large enough ((\sim 11'×14')) that it contains the entire dense core observed in previous dust continuum surveys. The dense gas traced by (NH_{3}(1,1)) covers a much larger area than the dust continuum features found in bolometer observations. The velocity dispersion in the central region of the core is small, presenting subsonic non-thermal motions which are independent of scale. However, it is because of the coverage and high sensitivity of the observations that we present the detection, for the first time, of the transition between the coherent core and the dense but more turbulent gas surrounding it. This transition is sharp, increasing the velocity dispersion by a factor of 2 in less than 0.04 pc (the 31'' beam size at the distance of Perseus,(\sim 250 pc)). The change in velocity dispersion at the transition is ( \approx 3 km \ s^{-1} \ pc^{–1}). The existence of the transition provides a natural definition of dense core: the region with nearly constant subsonic non-thermal velocity dispersion. From the analysis presented here, we can neither confirm nor rule out a corresponding sharp density transition.

We present a study on the impact of molecular outflows in the Perseus molecular cloud complex using the COMPLETE Survey large-scale (^{12}CO(1-0)) and (^{13}CO(1-0)) maps. We used three-dimensional isosurface models generated in right ascension-declination-velocity space to visualize the maps. This rendering of the molecular line data allowed for a rapid and efficient way to search for molecular outflows over a large ((\sim16 deg^2)) area. Our outflow-searching technique detected previously known molecular outflows as well as new candidate outflows. Most of these new outflow-related high-velocity features lie in regions that have been poorly studied before. These new outflow candidates more than double the amount of outflow mass, momentum, and kinetic energy in the Perseus cloud complex. Our results indicate that outflows have significant impact on the environment immediately surrounding localized regions of active star formation, but lack the energy needed to feed the observed turbulence in the entire Perseus complex. This implies that other energy sources, in addition to protostellar outflows, are responsible for turbulence on a global cloud scale in Perseus. We studied the impact of outflows in six regions with active star formation within Perseus of sizes in the range of 1-4 pc. We find that outflows have enough power to maintain the turbulence in these regions and enough momentum to disperse and unbind some mass from them. We found no correlation between outflow strength and star formation efficiency (SFE) for the six different regions we studied, contrary to results of recent numerical simulations. The low fraction of gas that potentially could be ejected due to outflows suggests that additional mechanisms other than cloud dispersal by outflows are needed to explain low SFEs in clusters.