Herschel observation of light hydrides and CS in NGC 3603
Markus Roellig, Volker Ossenkopf and the whole WADI-team
To study the chemical processes and physical conditions of light hydrides in photodissiciation regions (PDRs), we selected good tracers of the fluctuations of local density and temperature or kinematics and chemical state (e.g. C2H, CH, HCO+), and observed them in the framework of the Herschel Guaranteed Time Key Project 'The warm and dense ISM'. We detected the hyperfine components of CH in its ground state and we mapped HCO+(6−5) line, CS(11−10) and two hyperfine components of C2H. We present comparisons between our maps with NANTEN2 maps of CO and CI lines, and 8 micron Spitzer/IRAC data. We determine the abundance ratios of the observed species and their physical parameters. We study the distributions of the observed species and we find differences in positions of the peak of light hydrides and CO, CI lines. The peak of CS(11−10) is closer to the ionization front than CS(2−1) which indicates that the excitation of CS(11−10) is dominated rather by the gas heating from the cluster than by the higher density.