Star formation around W48A, a three-stage rocket?
D. Polychroni, M. Pestalozzi, G. Busquet, Q. Nguyen-Luong, F. Motte, S. Molinari, and the IFSI and HOBYS team
The ultracompact HII region W48A is surrounded by a much larger PDR shaped as a bow shock and is visible in the 70 micron images of Herschel. In front of the bow shock, cold gas streamers, oriented away from the shock front, were observed in deuterated ammonia (Pillai et al. 2011). Though earthbased telescopes were unable to detect the dust emission, the Herschel SPIRE maps find the dust counterpart of the cold gas streamers. Around W48A different stages of star formation are found; the UCHII region, an infrared object with an outflow thus actively forming stars, and still infrared dark, cold and dense clumps. We investigate the shape of W48A's surroundings and the star formation inside it by using the clump masses and temperatures determined from the Herschel maps combined with archival radio recombination line and ammonia observations.