FOLLOW-UP STUDIES OF VERY YOUNG INTERMEDIATE AND HIGH MASS STAR FORMING REGIONS DETECTED BY THE ISOPHOT SERENDIPITY SURVEY

摘要

We report results from our search for very young high-mass star forming regions using the 170 μm ISOPHOT Serendipity Survey. A total sky coverage of 15% makes this survey of the ISO satellite the largest one ever performed in the unexplored FIR beyond the IRAS 100 μm band. It is particularly sensitive to cold dust condensations with a dust temperature below 18 K. The cold and luminous FIR emitters of our sample were identified by a cross-correlation of cold sources in the ISOSS database coinciding with infrared sources detected by the 2MASS, MSX and IRAS surveys. The low temperature and large mass of the cold circumstellar matter in these objects, which has not yet been dispersed, indicates a recent begin of star formation. In order to explore the early evolutionary stage of these objects, we have initiated follow-up campaigns at (sub)mm (SCUBA, MAMBO), infrared (MAX, TIMMI2) and radio wavelengths (Effelsberg 100m-telescope). While ISO-PHOT allowed us to measure the peak of thermal dust emission, the combination with ground based mm-continuum measurements of high spatial resolution is essential for investigating the morphology of the dust component. Optical and infrared observations were targeted on embedded (proto)stellar sources, ammonia observations were performed in order to probe the dense gas. Our approach of multi wavelength characterization is demonstrated in detail for the newly discovered object ISOSS J 20298+3559. The observations revealed the presence of a molecular cloud complex with a total mass of 760 M_☉ and an average dust temperature as low as 16 K. Several massive cold cores without infrared counterparts have been found in coexistence with a luminous Herbig B2 star, which is the most evolved object in that complex. Spectroscopic signatures for ongoing mass infall towards the Herbig star give further evidence for the young age of the system.