A massive protostellar core with an infalling envelope

Abstract

Context: Due to the short timescales involved and observational difficulties, our knowledge of the earliest phases of massive star formation remains incomplete.
Aims: We aim to explore the physical conditions during the initial phases of high-mass star formation and to detect a genuine massive (mass M > 8 M_⊙) protostar at an early evolutionary stage.
Methods: We have launched a multi-wavelength study of young and massive star-forming regions that were identified by the ISOPHOT Serendipity Survey (ISOSS) performed with the ISO space telescope. The follow-up observations include ground-based near-infrared imaging and (sub)mm continuum and molecular line measurements (both single-dish and interferometric), as well as mid- to far-infrared measurements with the Spitzer Space Telescope. The combined spectrophotometric data are used to determine source temperatures T and masses M.
Results: ISOSS J23053+5953 is a massive (M ~ 900 M_⊙, luminosity L ~ 2100 L_⊙) and cold (T ~ 17 K) star-forming region with two protostellar/protocluster candidates (T ⪉ 20 K and T ~ 17.5 K, M ~ 200 M_⊙ each). The low temperatures are strongly confined by the spectrophotometric Spitzer data in the FIR. Interferometric observations reveal that the colder core (SMM2) has a mass of M = 26 M_⊙ within a region of 8700 × 5600 AU and drives an outflow. It also shows signs of infall in both single-dish and interferometric measurements, and its luminosity can be explained by accretion. We also detect a large-scale jet that is traced by H2 emission.
Conclusions: The cold mm-core ISOSS J23053+5953 SMM2 is a promising candidate for a high-mass protostar in an early evolutionary stage and one of the few objects showing both infall signatures and jets as a sign of accretion.

Plateau de Bure FITS data are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/474/883