Grain growth in the Taurus molecular cloud

Interstellar grain growth in molecular clouds is an important but not well understood process. This thesis attempts to understand the physical processes that lead to growth of interstellar grains in a molecular cloud. Two growth mechanisms that are important with respect to evolution of a molecular clouds are coagulation and mantle formation. To achieve this goal we focus on the Taurus Molecular Cloud (hereafter TMC) complex. We obtained visual and IR photometric data of field stars towards TMC. These datasets were used to build the extinction curve and evaluated the ratio of total to selective extinction, R_V. Previous studies have linked increase in R_V to changes in the size distribution of the grains due to coagulation. Therefore, R_V values of field stars towards TMC were used to parameterize coagulation in this region. Next we obtained spectroscopic data in the 3.1 μm H₂O ice band to investigate mantle growth as a function of the optical depth in TMC. All these data were used to investigate which growth mechanism is dominant in TMC. UV extinction data have been shown to be very diagnostic of the dust properties in the interstellar medium. We have used UV extinction data for three field stars behind TMC to understand the grain properties along these lines of sight.; Although we tried to select highly reddened stars for this work, our sample was limited by the problem of obtaining good visual photometric data for stars with extinctions much higher than the threshold for ice detection. We have only three stars, with visual extinction larger than 6.0, that have good extinction data. Our results confirms the model suggested by Whittet et al. (2001) that the TMC is made up of two components, a diffuse screen in which dense clumps are embedded. But the dense clumps are further divided into two components. We also find that both mantle formation and coagulation occur in the clumps of TMC but mantle formation seems to be the dominant process responsible for changing the optical properties of dust.