36th Annual Report (2023-24)

174 artment of Physics, r Panchanan Barma University (CBPBU): om 01 April 2022 till 31 March 2023 (ionised lines, Lick indices, photometric and morphological properties). Subsequently, a K-means cluster analysis is carried out based on the 14 best chosen Independent Components to obtain 12 distinct homogeneous groups of spiral galaxies. Amongst these, 3 groups are the oldest ones, while 5 groups fall in the medium- aged category, 2 groups consist of only unbarred spirals, 1 group is the youngest one, and the remaining one is an outlier. There are clear indications of recurrent bar formation phenomena in many groups, consistent with a few previous simulation works. To study the robustness of the clusters with respect to the method of clustering, a second method of clustering by Gaussian Mixture. In another work, we revisit the problem of clustering 1318 new variable stars found in the Milky Way. Our recent work distinguishes these stars based on their light curves which are univariate series of brightness from the stars observed at discrete time points. This work proposes a new approach to look at these discrete series as continuous curves over time by transforming them into functional data. Then, functional principal component analysis is performed using these functional light curves. Clustering based on the significant functional principal components reveals two distinct groups of eclipsing binaries with consistency and superiority compared to our previous results. This method is established as a new powerful light curve-based classifier, where implementing a simple clustering algorithm is effective enough to uncover the true clusters based merely on the first few relevant functional principal components. Simultaneously, we discard the noise from the data study involving the higher-order functional principal components. Thus, the suggested method is very useful for clustering big light curve data sets, verified by our simulation study. Another study examines the effect of dark matter halos on the orbital and escape dynamics of stars in the central region of barred galaxies. A three-dimensional gravitational model with a central bulge, bar, disc, and dark matter halo (or simply dark halo) has been set up and analysed from the viewpoint of escape in open Hamiltonian systems. Additionally, this model has been examined separately for the dark halo profiles, oblate and NFW. In both circumstances, an escape mechanism, which corresponds to the bar ends, has been identified near the saddle points of the phase space. The escaping motion of stars is seen using orbital maps and Poincare´e surface section maps generated in various phase planes. Finally, the relationship between chaos and dark halo parameters such as mass, size, circular velocity, and nature has been studied. Our findings suggest that oblate dark halos are preferred over NFW dark halos for justifying the formation of full-fledged spiral arms and extended distribution of dark halos in giant spiral galaxies with supermassive black holes (SMBHs) at their centers. Again, the oblate dark halos will justify the emergence of less prominent or poor spiral arms and the core-dominated distribution of dark halos in dwarf and LSB galaxies in the absence of central SMBHs. On the other hand, extreme central baryonic feedback is required for the NFW halos to generate spiral patterns and such dark halos should be preferred for galaxies with extremely energetic centers. 1. Dependence of Star formation rate on different properties of molecular clouds, Ashok Mondal and Tanuka Chattopadhyay, New Astronomy, 2024, 108. https://doi.org/10.1016/j.newast.2023. 102182 2. Investigation of the effect of bars on the properties of spiral galaxies: a multivariate statistical analysis, P r a s e n j i t B a n e r j e e , T a n u k a Chattopadhyay and Asis Kumar Chattopadhyay, Communications in S t a t i s t i c s - S i m u l a t i o n a n d Computation, 2024, 53(3), 1216-1246 https://doi.org/10.1080/03610918.20 22.2039198 3. A new approach to Astronomical data analysis based on multiple variables, PublicationsusingICARDfacilities (Activities from 01 April 2023 to 31 March 2024) Prasenjit Banerjee, Asis Kumar Chattopadhyay and Soumita Modak, Advances in Astronomy, 2023, Article ID 8682054. https://doi.org/10.1155/2023/868205 4 4. Star formation histories of dwarf and g i a n t g a l a x i e s w i t h d i f f e r e n t supernovae-driven outflows: NGC 2403, NGC 628, Suparna Sau, Tanuka Chattopadhyay and Pratap Ray, New Astronomy. , 2023, 100. https://doi.org/10.1016/j.newast.2022. 101992 5. Effect of dark matter holes on barred galaxies' orbital and escape dynamics, De b a s i s h Mond a l a nd T a nu k a Chattopadhyay, The European Physical Journal-Plus, 2023, 138, 1144. https://doi.org/10.1140/epjp/s13360- 023-04715-6 6. Comparison among different clustering and c l ass i f i ca t i on t echn i ques : Astronomical data-dependent study, P r a s e n j i t B a n e r j e e , T a n u k a Chattopadhyay and Asis Kumar Chattopadhyay, New Astronomy, 2023, 100. https://doi.org/10.1016/j.newast.2022. 101973 1. Dipankar Banerjee: Variability of our nearest star, the Sun and its impact, M.K. Dasgupta Birth Centenary Celebration, Rajabazar Science College, University of Calcutta, September 01, 2023. 2. Ajit Kembhavi: The James Webb Space Telescope, M.K. Dasgupta Birth Centenary Celebration, Rajabazar Science College, University of Calcutta, September 01, 2023. 3. Tanuka Chattopadhyay: Clustering & Classification of Galaxies: A Multivariate Data Base Approach, M.K. Dasgupta Birth Centenary Celebration, Rajabazar Science College, University of Calcutta, September 01, 2023. LecturesorganisedbytheICARDCentreD