Research Interests

• Structures and Dynamics of the Interstellar Medium
• Large-scale gas  fragmentation and star formation in galaxies
• Gravitational Lensing as an Astrophysical Probe

•  Radio Interferometric techniques
• Challenges in observations of  HI 21-cm signal from the  Epoch of Reionization

• Steiner Trees and Soap Films
• Sandpile Problems

Publications  [ Google Scholar Link ]

Academic History
 

“The main objective of teaching is not to give explanations, but to knock at the doors of the mind,”  

IIT (BHU), Varanasi

• 2021-22: Autumn Semester

       PHY-311: Introduction to Astronomy and Astrophysics
       PYM-523: Astronomy and Astrophysics 
       PHY-202: Computational Physics
       PYM-411: Introduction to Computational Physics

• 2020-21: Spring Semester     

​       PHY-101: Classical Quantum and Relativistic Physics
        PHY-306: Classical Mechanics
        PYM-401:  Classical Mechanics
        PHY-504:   Advanced Classical Mechanics and Electrodynamics
        M Sc General Physics Lab [Online with Simulated Experiments]

• 2020-21: Autumn Semester

        PHY-311: Introduction to Astronomy and Astrophysics

• 2020-21: Spring Semester

        PHY-101: Classical Quantum and Relativistic Physics
        PHY-306: Classical Mechanics
         PYM-401:  Classical Mechanics
         PHY-504:   Advanced Classical Mechanics and Electrodynamics

• 2019-20: Autumn Semester

        PHY-101: Classical Quantum and Relativistic Physics
         PHY-311: Introduction to Astronomy and Astrophysics

• 2019-20: Spring Semester

        PHY-101: Classical Quantum and Relativistic Physics
          PHY-502: Advanced Classical Mechanics and Electrodynamics
          PYM-401: Advanced Classical Mechanics

• 2018-19: Autumn Semester

          PHY-504: Advanced Mathematical and Computational Physics
          PHY-311: Introduction to Astronomy and Astrophysics

• 2018-2019: Autumn Semester

• 2017-2018: Spring Semester

• 2016-2017: Autumn Semester

• 2016-2017: Spring Semester

• 2015-2016: Autumn Semester

• 2015-2016: Spring Semester

• 2015-2016: Autumn Semester

• 2014-2015: Spring Semester

• 2013-2014: Autumn Semester

• 2012-2013: Spring Semester

Collaborators:

• Prof. Somnath Bharadwaj, IIT Kharagpur
• Prof. Jayaram N. Chengalur, NCRA-TIFR, Pune
• Prof. Sugata P. Khastgir, IIT Kharagpur
• Dr. Ayesha Begum
• Dr. Nirupam Roy, IISC, Bangalore
• Dr. Abhirup Datta, IIT Indore
• Dr. Samir Chowdhuri, NCRA-TIFR

Ph. D. Students

• Pavan Viswakarma
• Jais Kumar
• Meera Nandakumar
• Urvashi

Undergraduate Students

• Rajat Raj
• Pranav Pravin

Past Students

• Nandini Sahu
• Vivek Gupta
• Abhishek Raj
• Gaurav Tomar
• Shyam H. Menon
• Soumyadeep Das
• Archisha A. Patki

• Physical Properties of the Interstellar medium of Galaxies

1. Our investigation of HI column density fluctuation from external spiral galaxies revealed hitherto unknown large-scale coherent structures. Most possible reason for the creation of these structures may be turbulence, at present we are investigating the generating physical processes. We use an estimator of the column density power spectrum that evaluates it directly from  the observed visibilities by the radio interferometers.
2. In order to understand the energetics of the large-scale structures seen in the external galaxies, we have proposed a visibility based estimator of the HI velocity fluctuation. At present this estimator is being used to capture the interesting dynamics in the ISM of spiral galaxies. 

1. The dissipation scale of the ISM turbulence is debated and observational evidence is feeble. We have observed the power spectrum of HI opacity fluctuation along a couple of lines of sight in our Galaxy and have inferred on the existence and characteristics of such structures at sub-parsec length scales. At present we are launching a survey of such HI structures by observing them in absorption in the direction of several supernovae remnants in the Galaxy.
2. We observed scale invarient structures at scales of a few tens of astronomical units along the line of sight of 3C138  in our galaxy. Such scale structures, though are not yet known to be common, but still requires interesting new physics to explain.

1. Turbulence-induced fragmentation isolates the HI clouds at large scales and helps them to start the gravitational collapse. Given the observed  turbulence, we expect this to play a significant role in cascading the galactic rotational energy to small scales may eventually triggering an evolution from spiral to elliptical. We are using numerical hydrodynamic simulation to investigate the efficacy of turbulent cascade in energy transfer across scales in the galaxies.
2. Turbulent pressure may play an important role in the thermodynamics of the multiphase ISM. We are involved in a project to investigate the effect of turbulence driven random motion in the thermal balance and hence  stability  of different phases in the ISM.

• Observational aspects of  radio astronomy

1. Radio interferometers observe the visibility function, approximately the spatial Fourier transform of the sky brightness distribution. Several statistical estimators are used to infer the properties of the sky from the observed visibilities. We are involved in investigating the efficacy of these estimators and benchmark, prefer or reject them based on results from simulated observations of the model sky. We also are involved in developing statistically viable unbiased and low-risk estimators of one and two-point statistics of the sky brightness distribution from the interferometric observations.
2. Calibration and high dynamic range observation using radio interferometeris challenging. On top of this, existence of Foregrounds for the Epoch of Reionization observations provides the immense challenge for future experiments in these lines. We are at present in process of accessing the calibration requirements for the planned  intensity mapping experiments with the Square Kilometer Array (SKA) and other instruments. With the normal calibration, polarization leakage from the cross dipoles are expected to affect the intensity mapping experiments, we are investigating the instrumental requirements and improved strategies for polarization calibration.

• Tools for Gravitational Lensing with Radio Interferometers

1. With future telescopes like SKA, it will be possible to observe lensed radio images of high redshift galaxies. Such observations would let us have spatially resolve observations of galaxies at high redshifts and investigate the spatial structure of the ISM therein. We are involved in generating observational tools and providing theoretical prediction for such observations. 

Astronomical Software Developments 

*Repository will be available soon