An infrared-submillimeter study of starforming regions selected by the ISOSS 170 μm survey

Max-Planck-Institut für Astronomie (MPIA), Königstuhl 17, 69117 Heidelberg, Germany e-mail: hennemann@mpia.de

Received: 10 January 2008
Accepted: 7 April 2008

Abstract

Context. Using the ISOPHOT Serendipity Survey (ISOSS) at 170 μm, a sample of galactic starforming regions has been established that exhibits very cold dust temperatures (< K) and high masses (>100 ).

Aims. We characterize the starforming content of five regions that were selected as potential sites of high-mass star formation in early stages.

Methods. We used SCUBA (JCMT) observations in the submillimeter to identify the dense condensations of cold gas and dust. Sensitive mid- to far-infared Spitzer observations with IRAC and MIPS allowed us to detect associated young stellar objects. From the long-wavelength emission we derived dust temperatures and masses for the identified clumps. A sample of associated mid-infrared sources is investigated using infrared color-color diagrams and the comparison to a model SED grid to constrain their evolutionary stages and derive estimates for additional parameters like the central mass.

Results. In every region, we identified between one and four submillimeter clumps with projected sizes between 0.1 and 0.4 pc. The dust temperatures range from 11.6 to 21.3 K and the estimated clump masses are 2 to 166 . Towards the majority of submillimeter peaks, we found point sources in the near- to mid-infrared. Most are interpreted as low-mass young stellar objects, but we also detected very red sources. They probably represent very young and deeply embedded protostars that continue to accrete clump material and may reach higher masses. Several candidate intermediate-mass proto- or pre-main-sequence stars embedded in the clumps are identified.

Conclusions. A subset of four clumps may be massive enough (>100 ) to form high-mass stars and accompanying clusters. The absence of stellar precursors with current masses in the high-mass regime leave the type of star formation occurring in the clumps unsettled. We confirm the presence of large fractions of cold material as derived from large-scale far-infrared measurements that dominate the emission of most clumps and suggest that the starforming process will continue.