Electron temperatures in W51 complex from high resolution,low frequency radio observations |
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Authors: | P K Srivastava A Pramesh Rao |
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Institution: | 1.Dayanand Anglo-Vedic College,Kanpur,India;2.National Centre for Radio Astrophysics, Tata Institute of Fundamental Research,Pune University Campus,Pune,India |
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Abstract: | W51 is a giant radio complex lying along the tangent to the Sagitarius arm at a distance of about 7 kpc from the Sun, with
an extension of about 1° in the sky. It is divided into three components A, B, C where W51A and W51B consist of many compact
HII regions while W51C is a supernova remnant. We have made continuum radio observations of these HII regions of the W51 complex
at 240, 610, 1060 and 1400 MHz using GMRT with lower resolution (20″ × 15″) at the lowest frequency. The observed spectra
of the prominent thermal subcomponents of W51 have been fitted to a free-free emission spectrum and their physical properties
like electron temperatures and emission measures have been estimated. The electron temperatures from continuum spectra are
found to be lower than the temperatures reported from radio recombination line (RRL) studies of these HII regions indicating
the need for a filling factor even at this resolution. Also, the observed brightness at 240 MHz is found to be higher than
expected from the best fits suggesting the need for a multicomponent model for the region. |
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