Astronomy and Astrophysics – Astronomy
Scientific paper
Jun 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007basi...35..239s&link_type=abstract
Bulletin of the Astronomical Society of India, Vol. 35, pp.239-247
Astronomy and Astrophysics
Astronomy
Polarization, Stars: Formation, Ism: Clouds, (Ism:) Dust, Extinction, Ultraviolet: Ism, Instrument: Tauvex
Scientific paper
The small, compact dark clouds (also known as Bok Globules), are undergoing gravitational collapse that can result in the production of low mass stars. Light from background stars is scattered in forward direction by magnetically aligned dichroic dust grains. The degree and direction of alignment is proportional to the strength and direction of ambient magnetic field in the cloud. Background star polarimetry provides the technique to probe this field. In order to relate the physical conditions within the cloud to the background star polarization and to know the dust properties, we need to determine E(B-V) for each background star and relate it to the corresponding observed polarization (p). However, observed data, do not always show a correlation between polarization and extinction. Due to this the question arises whether the grains that produce polarization also produce observed extinction?
The observation that the polarization is not related to the extinction, can be explained if polarization and extinction are caused by two different grain populations. Polarization is mainly caused by short grains, whereas the extinction is caused by larger ones. Based on these findings, justifications are made here to detect these small grains (0.0035-0.01 mu m) in the star forming clouds through UV observations to be made by TAUVEX. These particles can be best detected through the UV observations, as they show far-UV excess and characteristic features of 2175 AA bump. We propose imaging of these clouds through the three bandpass filters of TAUVEX. We expect to resolve many unanswered questions associated with star forming clouds, through this set of proposed observations.
Gupta Rachana
Mukai Tadashi
Okada Yasuhiko
Sen Asok Kumar
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