Astronomy and Astrophysics Seminars
Probing Circumstellar Chemistry with the Submillimeter Array
by Dr. Nimesh Patel (Harvard-Smithsonian Center for Astrophysics, USA)
Tuesday, January 3, 2012
from
to
(Asia/Kolkata)
at Colaba Campus ( DAA Seminar Room A-269 )
at Colaba Campus ( DAA Seminar Room A-269 )
TIFR
Description |
Interstellar dust grains are thought to evolve in the colder regions of space from the gas and solids there, material believed to have come from Asymptotic Giant Branch (AGB) stars. The circumstellar envelopes of such stars are also rich in complex molecules. IRC+10216 is a well studied AGB star with a high mass loss rate. Close to the Sun (~150 pc), it is an ideal place to study the physical and chemical processes in AGB circumstellar envelopes. Using the Submillimeter Array (SMA), we recently carried out the first interferometric spectral line-survey of IRC+10216 in the 345 GHz band, with an angular resolution of 3"x2". 440 lines were detected, with more than half for the first time, and about a hundred lines that are as yet unassigned to known molecular transitions. Following this line survey of IRC+10216, we observed two more evolved stars: VY CMa and IK Tau, covering the same 870 microns window. From the distribution of molecules we are obtaining their abundances and isotopologic abundance ratios. Using data for multiple transitions in a number of molecules we are deriving the physical conditions in the circumstellar envelope to reach a picture of the star's chemistry that can be compared with models. Our legacy surveys are accompanied by a strong laboratory effort that helps with the identification of possibly newly found molecules traced by unidentified lines. We also plan to create a publicly accessible database of spectral-line channel-maps of the emission from all the lines detected in these surveys. |
Organised by | Dr. A. Gopakumar |