ISOPHOT observations of the ``NOBEYAMA'' dense cores in the RHO OPH cloud

M. Tamura ¹, K. Sunada ², T. Kamazaki ³, Y. Kitamura ⁴, T. Umemoto ¹, M. Saito ², & Y. Oasa ³

¹ National Astronomical Observatory of Japan

² Nobeyama Radio Observatory

³ University of Tokyo

⁴ Institute of Space and Astronautical Science

It is well known that the central region of the Rho Oph molecular cloud harbors a number of high density regions, so called dense cores. Recently we have established an unbiased and complete sample of such dense cores with the extensive surveys in the optically thin emission line with the Nobeyama Radio Observatory 45-m telescope. The sample consists of as many as 90 dense cores in the 40 square arcminutes. Searching for the possible precursor of Class 0/I sources and investigating the nature of the dense cores, we have conducted a deep far-infrared survey of the millimeter-wave selected sample of the dense molecular cloud cores. We have used ISO PHOT-C at 50, 105, and 180 micron, and ISO PHOT-P at 12.5, and 25 micron. These sensitive (down to 0.3 Jy at 105 micron) far-infrared surveys should clearly reveal the nature of the cores without IRAS sources. In fact, we have detected new sources which were not detected by IRAS. We have then identified several types of the dense cores based on the difference between the millimeter molecular line emission and the far-IR dust continuum emission. This difference might be attributed to the different evolutionary stages of the dense cores.