A multiwavelength study of the ultracompact HII region associated with IRAS 20178+4046^*

¹ Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India e-mail: tej@tifr.res.in
² National Centre for Radio Astrophysics, Post Bag 3, Ganeshkhind, Pune 411 007, India

Received: 27 September 2006
Accepted: 27 February 2007

Abstract

Aims.We present a multiwavelength study of the ultra compact HII region associated with IRAS 20178+4046. This enables us to probe the different components associated with this massive star-forming region.

Methods.The radio emission from the ionized gas was mapped at 610 and 1280 MHz using the Giant Metrewave Radio Telescope (GMRT), India. We used 2MASS  data to study the nature of the embedded sources associated with IRAS 20178+4046. Submillimetre emission from the cold dust at 450 and 850 μm was studied using JCMT-SCUBA.

Results.The high-resolution radio continuum maps at 610 and 1280 MHz display compact spherical morphology. The spectral type of the exciting source is estimated to be ~B0.5 from the radio flux densities. However, the near-infrared data suggest the presence of several massive stars (spectral type earlier than O9) within the compact ionized region. Submillimetre emission shows two dense cloud cores that are probably at different evolutionary stages. The total mass of the cloud is estimated to be ~700–1500  from the submillimetre emission at 450 and 850 μm.

Conclusions.The multiwavelength study of this star-forming complex reveals an interesting scenario where we possibly see different evolutionary stages in star formation. The ultra compact HII region coinciding with the southern cloud core is at a later stage of evolution compared to the northern core, which is likely to be a protocluster.