Temperature, kinematics and turbulence of infrared dark clouds (IRDCs) at high spatial resolution Simon Bihr MPIA Heidelberg, Heidelberg, Germany
While high-mass stars, such as OB stars, affect their environment significantly with uv-radiation or supernovae, they also influence the interstellar medium and the development within entire galaxies. Although their importance is undoubted, the formation process of massive stars remains poorly understood. Herschel gives us a unique chance to study dust properties of dense cores in details, but the bolometric data lack any kinematical information. Therefore, we have embarked on an eVLA NH_3 study to investigate the temperatures, kinematics and turbulent properties of the dense gas in a sample of Herschel selected infrared dark clouds (IRDCs). We observed the NH_3 (1,1) and (2,2) transition lines towards seven IRDCs with the eVLA at high spatial resolution of ~3" (~9000AU) in 2010 and we will observe a part of this sample with the Effelsberg 100m telescope in January 2012. In my talk/poster, I will present the results of these observations. Due to the high resolution of ~ 3" we are able to spatially resolve the kinematics and turbulence within the IRDCs. As the temperature of IRDCs is in the range of 10-20K, ammonia can also be used as a thermometer. Therefore we are able to determine temperature maps and we find decreasing temperature gradients from the cloud edges toward the dark cloud centers. These cold dense clumps have no 24 mu m counterpart, that means no embedded heating source. Hence they represent the earliest stage of massive star formation. Another result of our ammonia observations is to probe directly the collisional coupling regime between dust and gas within star-forming regions. Herschel data allows us to derive accurate dust temperature maps and density distributions. Because our ammonia observations reveal gas temperature maps, we can compare both temperatures within different density regimes.
Collaborators: H. Beuther, MPIA Heidelberg, Germany