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I am an Associate Professor in the Department of Astronomy, Astrophysics and Space Engineering (DAASE) at Indian Institute of Technology, Indore. I have joined IIT Indore as an Assistant Professor in May 2018. I have been promoted to the position of Associate Professor in November 2022. I have received my Ph.D. (Apr, 2013) degree in physics (cosmology) from Indian Institute of Technology, Kharagpur, India, under the supervision of Prof. Somnath Bharadwaj and Prof. Sugata Pratik Khastgir. Before joining at IIT Indore, I was a Research Associate in the Astrophysics Group at Imperial College London, UK (Nov, 2015 - April, 2018). At Imperial, I have worked in the research group of Prof. Jonathan R. Pritchard. Before that, I was a Postdoctoral Fellow in the Department of Astronomy at Stockholm University (Dec, 2012 - Nov, 2015) and worked in the research group of Prof. Garrelt Mellema.

CV»

I am presently leading the Cosmology with Statistical Inference (CSI) research group at IIT Indore.

Cosmology is the study of the evolutionary history of our universe. I am specifically interested in studying the period when the first stars and galaxies were formed (Cosmic Dawn - CD) and then they gradually changed the phase of most of the visible matter in our universe from neutral to ionized (Epoch of Reionization - EoR). My research focuses on the possibility of using the existing (e.g. GMRT, LOFAR, MWA, PAPER etc) and the upcoming (Square Kilometre Array - SKA) radio telescopes, along with telescopes at other wavelengths (e.g. Euclid, Athena, WFIRST, JWST, ELT, TMT, SPHEREx, TIME, CONCERTO etc.) to learn about this mysterious mostly unexplored chapter in the history of our universe. These observations will open up a new window onto the early Universe and will give us much better insight about formation of the Large Scale Structures in our Universe.

I am a member of the “Epoch of Reionization and the Dark Ages” international science working group for the SKA. I am also a member of the “Epoch of Reionization” science working group for the LOFAR International Telescope and the “Square Kilometre Array - India” collaboration for the “Cosmic Dwan and the Epoch of Reionization”. I am a long term visitor in the Astrophysics Group at Imperial College London, UK and in the Astroparticle Physics Group at SISSA, Trieste, Italy. I am PI of several ongoing externally funded research projects.

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Research

One of the most important missing pictures in our cosmic history is the Cosmic Dawn (CD) and the Epoch of Reionization (EoR), the period during which the very first sources of light were formed. The radiation emitted by these sources gradually heated and “re”-ionized the neutral and cold hydrogen (HI) in their surrounding inter-galactic medium (IGM).

Many fundamental issues regarding this era, such as its timing, duration, and the properties of the sources driving it, are still unresolved. Observations of the redshifted 21-cm signal, emitted by the HI from this era, hold a great promise to resolve many of these puzzles. The observation of this signal effectively allows us to "time travel" and see the state of the IGM during this era as a time lapse movie.

Very recently, the EDGES might have detected the very first glimpse of this signal from Cosmic Dawn. Several other radio telescopes around the world are currently in a race to detect this signal in great detail (for example -- GMRT, LOFAR, MWA, PAPER, 21CMA). The upcoming enormous Square Kilometre Array (SKA), an international radio telescope of which India is also a major member, is expected to be able to image the HI distribution at different cosmic times from the beginning to the end of this era, owing to its great sensitivity. Apart from the 21-cm signal from the IGM, these first luminous sources are expected to be visible via different line emissions at different other wavelengths. The future experiments e.g. Euclid, Athena, Roman Space Telescope (WFIRST), JWST, ELT, TMT, SPHEREx, TIME, CONCERTO etc. are expected to map the sources of CD-EoR via these atomic and molecular line emissions.

It is expected that in a decade or so we will be witnessing a tsunami of observational data of the CD-EoR coming from these next-generation telescopes. Thus it would be crucial to develop effective and fast interpretation pipeline for these observations to answer the unresolved questions regarding this epoch. My research is focused towards building such optimal interpretation pipelines for the future observations of the CD-EoR.

Any interpretation pipeline is made up of several important segments, in the context of CD-EoR observations they are, realistic and fast simulations of the expected signal, modelling the response of the telescope, developing statistics for the signal detection and optimal parameter estimation from the detected signal. In the CSI research group we work on many of these aspects. Below you will find a non-exhaustive list of areas in which we are presently working.

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Simulations of the Signals from CD-EoR

21-cm line from the neutral IGM

We have developed a fast semi-numerical simulation (Sem-Num) of the CD-EoR 21-cm signal expected at low-frequency radio interferometers. Our simulation has been tested and validated against state-of-the art computationally expensive radiative transfer simulations (Majumdar et al. 2013, 2014). These simulations have been further optimized by Rajesh Mondal and now available by the name of ReionYuga.

CII Line Intensity Mapping to observe the Early Galaxies

We have developed a semi-numerical code (Murmu et al. 2021) for simulating singly ionized carbon line (CII) from the early star forming galaxies. This emission, from the galaxies in CD-EoR era, will reach us in far infrared and radio wavelengths after being cosmologically redshifted. Using instruments line ALMA, TIM, CONCERTO etc one can make coarse images (Line Intensity Maps - LIM) of this signal. These LIMs along with 21-cm maps will help us to answer many unresolved questions related to the CD-EoR.

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Statistics of the Signals from CD-EoR

Power Spectrum

One would need to define adequate statistics to quantify and interpret the signals detected from the CD-EoR. The first statistics that will be used in case of both 21-cm and CII signal detection and interpretation is the power spectrum (due to its high signal-to-noise ratio). Power spectrum represents the amplitude of fluctuations in the signal in different length scales. The time evolution of the signal power spectrum may provide us a wealth of information about the reionization timeline and its sources. Using simulated signal, we have extensively studied several line-of-sight anisotropies that will be inherently present in the power spectrum (e.g. Redshift Space Distortions and Light Cone Effect -- Majumdar et al. 2013, 2014, 2015, Datta et al. 2014 etc.). We have shown that if these anisotropies are not taken into account one might interpret the signal wrongly. Additionally these line-of-sight anisotropies can be used to extract the reionization history from the signal.

Bispectrum

The CD-EoR 21-cm signal is highly non-Gaussian and thus the power spectrum cannot describe the signal completely as it is unable to capture this non-Gaussianity in the signal. One would need a higher order statistics e.g. bispectrum to probe this time evolving non-Gaussianity. The bispectrum is estimated by forming closed triangles in the Fourier domain and depending on the triangle shape and size different features of the signal non-Gaussianity are probed. We are the first to eastimate CD-EoR 21-cm bispectrum for all unique triangles in Fourier domain from the simulated signal (Majumdar et al. 2020, Kamran et al. 2021a). We are also the first to point out that the sign of the bispectrum holds key to identify the source of non-Gaussianity (Majumdar et al. 2018). We have also quantified the impact of Redshift Space Distortions on the bispectrum. We have also been able to connect the IGM physics with the time evolution of the bispectrum (Kamran et al. 2021b). We have also shown that one can distinguish very clearly between different dark matter models through the 21-cm bispectrum (Saxena et al. 2020). Additionally, we have shown that it is possible to extract the linear and quadratic bias factors more accurately by analyzing the post-EoR 21-cm bispectrum (Sarkar et al. 2019). In many ways we have been doing pioneering work in the domain of 21-cm bispectrum, which has resulted in more than 12 publications on this topic from our group, you can find them here.

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Bayesian Inference and Machine Learning

The final aim of any observational campaign to explore the CD-EoR is to draw statistical inference about the possible physical models of this era. To draw such the statistical inference from the future SKA observations of the CD-EoR we have developed a Bayesian inference pipeline that allows us to constrain the CD-EoR parameters from observables. As the 'models' (i.e. 'simulations') of the CD-EoR are computationally expensive, in our Bayesian inference pipeline thus we have replaced the 'simulated signal statistics' with Artificial Neural Network 'emulated signal statistics' (for more details see our Bayesian inference pipeline and ANN emulator for 21-cm power spectrum and bispectrum -- EmuPBk). We have also demonstrated that the 21-cm bispectrum can put better constraints on the CD-EoR parameters compared to 21-cm power spectrum (Tiwari et al. 2021).

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Images of the Cosmic Dawn through Multi-wavelength Observations

The SKA will be able to make for the first time high-definition tomographic images of the IGM during CD-EoR. These images can potentially provide us a huge amount of information about the CD-EoR. We have developed a variety of image analysis techniques to extract this crucial information from the 21-cm maps. Some of these methods are Matched Filtering (Datta et al. 2008, Majumdar et al. 2011, 2012 etc.), Granulometry (Kakiichi et al. 2017), Largest Cluster Statistics (Bag et al. 2018, Pathak et al. 2022) etc. These image analysis methods allow us to constrain the properties of very bright sources of the EoR and the local IGM (Majumdar et al. 2011, 2012 etc.), allow us to understand the reionization topology and through it characteristics of the ionizing sources (Kakiichi et al. 2017, Bag et al. 2018, Pathak et al. 2022), and allow us to develop strategies for synergistic multi-wavelength observations of the CD-EoR (Zackrisson et al. 2020) with the upcoming Euclid, Roman Space Telescope (WFIRST), JWST, ELT, TMT etc.

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Research Group

• We are always looking for highly motivated and enthusiastic PhD and Master's students to join the group. Please check our PhD advertisement here -- https://academic.iiti.ac.in/phdadvt.php. Deadline to apply is 15 May 2023. If you are interested in joining the group please contact me with your CV via email at suman.majumdar at iiti.ac.in.

PhD Students:

Leon Noble (July 2022 - Ongoing)
Research Area: Developing statistical inference pipeline for multi-wavelength observations of the Universe

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Chandra Shekhar Murmu (July 2019 - Ongoing)
Research Area: Studying the early Universe through cross-correlations of multi-wavelength observations
Publications:

• CII and HI 21-cm line intensity mapping from the EoR: Impact of the light-cone effect on auto and cross-power spectra, MNRAS, 507, 2, 2500-2509, (2021), arXiv:2107.09072.
• Revisiting the [C II]158μm line-intensity mapping power spectrum from the EoR using non-uniform line-luminosity scatter, MNRAS, January (2023), arXiv:2110.10687.
• Probing the Epoch of Reionization using synergies of line intensity mapping, JoAA, October (2022), arXiv:2210.09612.

Conference Presentations:

• Poster at the SAZERAC-SIP on The 21-cm Signal from Cosmic Dawn and the Epoch of Reionization (29 January 2021).
• Poster at the Astronomical Society of India Meeting 2021 (18-23 February 2021).
• Poster at the A Precursor View of the SKA Sky (15-19 March 2021).
• Talk at the SKA-India Workshop on 21-cm Cosmology and Reionization (19-23 April 2021).
• Poster at the 4th Global 21-cm Workshop (11-14 October 2021).
• Talk at the SKA CD-EoR Science Working Group Meeting, Scuola Normale Superiore, Pisa, Italy (27-29 September 2022).
• Talk at the Workshop on 21-cm Cosmology in SKA Era, Indian Statistical Institute, Kolkata, India (31 October - 4 November 2022).

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Mohd Kamran (July 2018 - Nov 2022)
Postdoc at Uppsala University, Sweden.
Research Area: Quantifying the non-Gaussianity in the 21-cm signal from the Cosmic Dawn
Publications:

• Redshifted 21-cm Bispectrum I: Impact of the Redshift Space Distortions on the Signal from the Epoch of Reionization, MNRAS, 499, 4, 5090-5106, (2020), arXiv:2007.06584.
• Redshifted 21-cm Bispectrum II: Impact of the Spin Temperature Fluctuations and Redshift Space Distortions on the Signal from the Cosmic Dawn, MNRAS, 502, 3, 3800-3813, (2021), arXiv:2012.11616.
• Probing IGM Physics during Cosmic Dawn using the Redshifted 21-cm Bispectrum, Under Review, (2021), arXiv:2108.08201.
• Redshifted 21-cm bispectrum: Impact of the source models on the signal and IGM physics from the Cosmic Dawn, JCAP, November (2022), arXiv:2207.09128.

Conference Presentations:

• Talk at the International Conference on Observing the First Billion Years of the Universe using Next Generation Telescopes, IIT Indore, India (20-24 January 2020).
• Talk at the SUMMER ALL ZOOM EPOCH OF REIONIZATION ASTRONOMY CONFERENCE (6-9 July 2020).
• Talk at the 3rd Global 21-cm Workshop, Cambridge University, UK (19-22 October 2020).
• Talk at the SAZERAC-SIP on The 21-cm Signal from Cosmic Dawn and the Epoch of Reionization (29 January 2021).
• Talk at the A Precursor View of the SKA Sky (15-19 March 2021).
• Talk at the SKA-India Workshop on 21-cm Cosmology and Reionization (19-23 April 2021).
• Poster at the 4th Global 21-cm Workshop (11-14 October 2021).
• Talk at the SKA CD-EoR Science Working Group Meeting, Scuola Normale Superiore, Pisa, Italy (27-29 September 2022).

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Master's Project Students:

Priyatam Kumar Mahto (July 2022 - ongoing)
M.Sc. Astronomy (2023).
Co-supervisor: Dr. Erik Zackrisson, Uppsala University, Sweden.
Research Area: Searching for extra-terrestrial intelligence through multi-wavelength observations.

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Vednarayan Iyer (July 2022 - ongoing)
M.Sc. Astronomy (2023).
Will join as a PhD student (starting in October 2023) in the University of Alabama, USA.
Research Area: Building an accurate semi-numerical simulation for the Cosmic Dawn 21-cm signal.

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Saswata Dasgupta (July 2021 - ongoing)
MS (Research) in Space Science and Engineering (2023).
Will join as a PhD student (starting in October 2023) in the Institute of Astronomy, Cambridge University, UK.
Research Area: Analysis of the 21-cm images from the Cosmic Dawn.
Publications:

• Distinguishing reionization models using the largest cluster statistics of the 21-cm maps, JCAP, November (2022), arXiv:2202.03701.
• Interpreting the HI 21-cm cosmology maps through Largest Cluster Statistics -- I: Impact of the synthetic SKA1-Low observations, JCAP, May (2023), arXiv:2302.02727.

Conference Presentations:

• Talk at the Workshop on 21-cm Cosmology in SKA Era, Indian Statistical Institute, Kolkata, India (31 October - 4 November 2022).
• Talk at the SKA CD-EoR Science Working Group Meeting, Scuola Normale Superiore, Pisa, Italy (27-29 September 2022).

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Sohini Dutta (July 2021 - July 2022)
M.Sc. Astronomy (2022).
Working as a Data Scientist at American Express.
Selected for PhD positions at Swinburne University, University of Heidelberg, Cambridge University and Manchester University.
Will join the PhD position in Manchester University., UK (starting in October 2023).
Research Area: Constraining reionization parameters using 21-cm and CII cross-power spectrum.
Conference Presentations:

• Talk at the Workshop on 21-cm Cosmology in SKA Era, Indian Statistical Institute, Kolkata, India (31 October - 4 November 2022).
• Talk at the SKA CD-EoR Science Working Group Meeting, Scuola Normale Superiore, Pisa, Italy (27-29 September 2022).

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Kunal Motghare (July 2021 - July 2022)
M.Sc. Astronomy (2022).
Research Area: Understanding the 21-cm marked power spectrum from the post-reionization era.

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Aadarsh Pathak (August 2020 - July 2021)
M.Sc. Astronomy (2021).
PhD student at the University of Melbourne, Australia.
Research Area: Exploring the topology of the hydrogen distribution in the early universe.
Publications:

• Distinguishing reionization models using the largest cluster statistics of the 21-cm maps, JCAP, November (2022), arXiv:2202.03701.
• Interpreting the HI 21-cm cosmology maps through Largest Cluster Statistics -- I: Impact of the synthetic SKA1-Low observations, JCAP, May (2023), arXiv:2302.02727.

Conference Presentations:

• Poster at the Astronomical Society of India Meeting 2021 (18-23 February 2021).
• Poster at the SAZERAC-SIP on The 21-cm Signal from Cosmic Dawn and the Epoch of Reionization (29 January 2021).
• Talk at the A Precursor View of the SKA Sky (15-19 March 2021).
• Talk at the SKA-India Workshop on 21-cm Cosmology and Reionization (19-23 April 2021).
• Poster at the 4th Global 21-cm Workshop (11-14 October 2021).

Public Outreach:

• Making bilingual (English + Hindi) videos on YouTube to explain several concepts of cosmology and astrophysics.

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Anchal Saxena (July 2019 - July 2020)
M.Sc. Astronomy (2020).
Recepient of the Insititute Medal for the Best M.Sc. Project of 2020 (among all M.Sc. students accross all disciplines).
PhD student at the University of Groningen, the Netherlands.
Research Area: Impact of dark matter models on the EoR 21-cm signal.
Publications:

• Impact of dark matter models on the EoR 21-cm signal bispectrum, MNRAS, 497, 3, 2941-2953, (2020), arXiv:2004.04808.

Conference Presentations:

• Poster at the International Conference on Observing the First Billion Years of the Universe using Next Generation Telescopes, IIT Indore, India (20-24 January 2020).
• Talk at the SUMMER ALL ZOOM EPOCH OF REIONIZATION ASTRONOMY CONFERENCE (6-9 July 2020).
• Talk at the 3rd Global 21-cm Workshop, Cambridge University, UK (19-22 October 2020).

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Himanshu Tiwari (July 2019 - July 2020)
M.Sc. Astronomy (2020).
PhD student at Curtin University, Australia.
Research Area: Developing Artificial Neural Network based Bayesian inference tools for the future observations of the Cosmic Dawn and the Epoch of Reionization.
Toolbox developed:

• EmuPBk: A Bayesian parameter estimation pipeline built on an ANN based emulator of the 21-cm power spectrum and bispectrum.
• FRBe: A Bayesian based maximum likelihood estimator of the parameters of the observed FRB population.

Publications:

• A maximum likelihood estimate of the parameters of the FRB population, MNRAS: Letters, 2021, arXiv:2109.06785.
• Improving constraints on the reionization parameters using 21-cm bispectrum, JCAP, April 2022, arXiv:2108.07279.
• Modelling the energy distribution in CHIME/FRB Catalog-1, MNRAS, 2022, arXiv:2209.12961.

Conference Presentations:

• Talk at the SUMMER ALL ZOOM EPOCH OF REIONIZATION ASTRONOMY CONFERENCE (6-9 July 2020).
• Talk at the 3rd Global 21-cm Workshop, Cambridge University, UK (19-22 October 2020).

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Samanvith A (July 2019 - July 2020)
M.Sc. Astronomy (2020).
Research Area: Visualizations of the Epoch of Reionization.

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Grants

Following are the externally funded research grants awarded to the group:

• Illuminating the Dark Sector of the Cosmos in the SKA Era, (approx. INR 80 lakhs), (2024-2026),
  PI: Suman Majumdar, in Collaboration with SISSA, Trieste and SNS, Pisa, Italy.
  Funding Agency: SPARC, ME, GoI.
• Galaxies through the ages: using synergistic multi-wavelength observations, (approx. INR 63 lakhs), (2023-2025),
  PI: Suman Majumdar, in Collaboration with the University of Sussex, UK and International Space Science Institute, Switzerland.
  Funding Agency: SPARC, ME, GoI.
• Observing the Cosmic Dawn in Multicolour using Next Generation Telescopes, (approx. INR 24.5 lakhs), (2022-2025),
  PI: Suman Majumdar.
  Funding Agency: SERB, Core Research Grant.
• Unveiling the Cosmic Dawn: novel techniques to study the reionization of the early universe, (Euro 6000), (2020-2023),
  PI: Suman Majumdar, in collaboration with Stockholm University, Sweden.
  Funding Agency: ASEM-DUO.
• Imaging the first billion years of the Universe with next-generation telescopes, (approx. INR 55 lakhs), (2019-2023),
  PI: Suman Majumdar, in Collaboration with Stockholm and Uppsala University, Sweden.
  Funding Agency: SPARC, MHRD, GoI.

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Publications

Most of my publications can be found in the following arXiv link:

https://arxiv.org/a/majumdar_s_1.html.

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News

• We had organized a course on Numerical Radiative Transfer (15-24 January 2024) at IIT Indore. Instructor of the course was Prof. Ilian T. Iliev, University of Sussex, UK.

• We are looking for highly motivated and skilled PhD and Master's students to join the group. Please check our PhD advertisement here -- https://academic.iiti.ac.in/phdadvt.php. Deadline to apply is 15 May 2023. If you are interested in joining the group please contact me with your CV via email at suman.majumdar at iiti.ac.in.

• We had organized a course on Numerical Astrophysical Gasdynamics (13-18 February 2023) at IIT Indore. Instructor of the course was Prof. Garrelt Mellema, Stockholm University, Sweden.

• We had organized a course on Searching for Extraterrestrial Intelligence (9-15 September 2022) at IIT Indore. Instructor of the course was Dr. Erik Zackrisson from Uppsala University, Sweden.

• We had organized a four day long (14-17 March 2022) international meeting on the cosmic 21 cm signal from the Dark Ages to the present day over zoom under the framework of SAZERAC.
  Please check the meeting website for details - SAZERAC 21cm 2022.

• We had organized an one day international meeting on the 21 cm signal from Cosmic Dawn and Epoch of Reionization over zoom under the framework of SAZERAC.
  Please check the meeting website for details - http://sazerac-conference.org/SIPS2021/3.html.

• We had organized an international conference and school in DAASE, IIT Indore on "Observing The First Billion Years of the Universe Using Next-Generation Telescopes" during 20-31 January 2020.
  For further details, please check the conference webpage.

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Teaching

2023 Spring semester:

AA 608: Astrostatistics
- shared with Dr. Abhirup Datta

AA 609: Computational Methods in Astronomy and Space Sciences
- shared with Dr. Bhargav Vaidya

2022 Autumn semester:

AA 471/671: Relativity and Cosmology
- shared with Dr. Manoneeta Chakraborty

AA 651: M.Sc. Astronomy Lab - I
-shared with Dr. Amit Shukla

2022 Spring semester:

AA 608: Astrostatistics
- shared with Dr. Saurabh Das and Dr. Abhirup Datta

AA 609: Computational Methods in Astronomy and Space Sciences
- shared with Dr. Bhargav Vaidya

2021 Autumn semester:

AA 471/671: Relativity and Cosmology
- shared with Dr. Siddharth S. Malu and Dr. Manoneeta Chakraborty

AA 651: M.Sc. Astronomy Lab - I
-shared with Dr. Anjali Rao

2021 Spring semester:

AA 608: Astrostatistics
- shared with Dr. Siddharth S. Malu and Dr. Saurabh Das

2020 Autumn semester:

AA 471/671: Relativity and Cosmology
- shared with Dr. Siddharth S. Malu

AA 301: High Energy Astronomy or Astrophysical Processes.
-shared with Dr. Siddharth S. Malu

2020 Spring semester:

AA 608: Astrostatistics
- shared with Dr. Amit Shukla

AA 698: M.Sc. Astronomy Seminar Course

2019 Autumn semester:

AA 471/671: Relativity and Cosmology
- shared with Dr. Siddharth S. Malu

AA 301: High Energy Astronomy or Astrophysical Processes.
-shared with Dr. Saurabh Das

2019 Spring semester:

AA 608: Astrostatistics
- shared with Dr. Saurabh Das and Dr. Manoneeta Chakraborty

AA 602: Advanced Topics in Astronomy and Astrophysics (Section: Large Scale Structures of the Universe)
- shared with Dr. Bhargav Vaidya.

AA 652: Astronomy Laboratory-II (Section: Optics)
- shared with Dr. Abhirup Datta and Dr. Manoneeta Chakraborty.

2018 Autumn semester:

AA 301: High Energy Astronomy or Astrophysical Processes.

AA 651: Astronomy Laboratory-I (Section: Basics of Numerical Methods in Astrophysics and Cosmology)
- shared with Dr. Abhirup Datta, Dr. Bhargav Vaidya, Dr. Manoneeta Chakraborty and Dr. Saurabh Das.