Abstract Details
| Name: samyaday choudhury Affiliation: IISc (JAP), IIA Conference ID: ASI2016_543 Title : Study of evolved stellar populations in the Magellanic Clouds Authors and Co-Authors : Abstract Type : Oral Abstract Category : Thesis Abstract : The Magellanic Clouds (MCs), comprising of the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC) are two nearby (~50 kpc), interacting galaxies to our Milky Way. In my thesis I have studied the sparse star clusters and metallicity distribution for one of the component of the MCs, the LMC. The study of sparse star clusters in the LMC is important in order to understand the cluster formation history of the LMC. The study aims to increase our understanding of sparse star clusters in the LMC, using deep Washington photometric data of 45 star clusters obtained from 4-m Blanco Telescope, CTIO. A systematic study was performed to estimate their parameters (radius, reddening, and age) using the main-sequence turn-off, as well as the evolved portion of the color-magnitude diagram (CMD). The basic parameters were estimated for 33 clusters, out of which 23 are identified as single clusters and 10 are found to be members of double clusters. The other 12 clusters are classified as possible clusters/asterisms. The sizes (~2-10 pc) and masses (~a few 100 - 1000 Msun) of these 45 inconspicuous clusters emphasises that the LMC has a significant population of clusters, which are similar to the open clusters in our Galaxy. To understand the metallicity distribution and gradient of the LMC, we estimated a metallicity map using the red giant branch (RGB) stars, from the Magellanic Cloud Photometric Survey (MCPS) and Optical Gravitational Lensing Experiment (OGLE III) photometric data. This is a first of its kind map of metallicity up to a radius of 4º - 5º , with good sampling of the bar region. The slope of the RGB is used as an indicator of the average metallicity of a subregion, and it is calibrated to metallicity using spectroscopic data for field and cluster red giants in selected subregions. The average metallicity of the LMC is found to be [Fe/H] = −0.37 dex (σ[Fe/H] = 0.12) from MCPS data, and [Fe/H] = −0.39 dex (σ[Fe/H] = 0.10) from OGLE III data. The bar is found to have an uniform and higher metallicity compared to the disk, and is indicative of an active bar in the past. Both the data sets suggest a shallow radial metallicity gradient up to a radius of 4 kpc (−0.049 ± 0.002 dex/kpc to −0.066 ± 0.006 dex/kpc ). This metallicity gradient of the LMC disk, though shallow resembles the gradient seen in spiral galaxies, and is also similar to that found in our Galaxy. |