Shishir Sankhyayan

Visiting Fellow
Email: sankhyayan [at]
Phone: 020-2571 9218
Extn: 9218
Office: 218A
National Centre for Radio Astrophysics
Tata Institute of Fundamental Research
Savitribai Phule Pune University Campus,
Pune 411 007
Maharashtra, INDIA

Main Research Areas: Large scale structure; Superclusters; Voids; Galaxy clusters; Structure formation


Shishir Sankhyayan obtained a B.Sc. in Physics in 2008 from the University of Lucknow, an M.Sc. in Physics in 2010 from the University of Pune, and a Ph.D. in 2019 from the Indian Institute of Science Education and Research, Pune. He was also an Educator in 2010 and 2011 at the Indira Gandhi Planetarium, Council of Science and Technology, Lucknow, a Teaching Assistant between 2011 and 2012 at the Indian Institute of Science Education and Research, Pune, and a Tutor between 2011 and 2012 at the Centre of eLearning & Training, Pune. He joined NCRA-TIFR in January 2020 as a Visiting Post-doctoral Fellow.

Research description:

In the Universe, galaxies and dark matter are distributed in the intricate network of the Cosmic Web. The Cosmic Web consists of clusters, filaments, walls, and voids. The largest structures in the Universe are superclusters (clusters of clusters) and voids, spanning tens to hundreds of Megaparsec (Mpc) length scales. Superclusters are very rare structures and the physical processes of their origin and evolution are still unclear. Therefore, identifying and studying such structures is very important for a complete understanding of the evolution of the large-scale structure of the Universe. While superclusters are vast overdense regions, voids are the underdensities with almost no galaxy. The dark energy density is higher than the dark matter density inside voids and, therefore, governs the dynamics. Voids are instrumental in the spatial organization of the Cosmic Web. My research involves identifying superclusters and voids from optical galaxy redshift surveys, and studies of their properties and cross-correlation attributes. I am involved in the study of Saraswati supercluster at radio wavelengths, using the upgraded Giant Meterwave Radio Telescope. I also study the cosmic web environment around Giant Radio Galaxies, which are the largest galaxies known in the radio band, with projected linear sizes greater than 700 kpc. These are very rare objects and the cosmic web environment is believed to be one of the factors affecting their sizes.

Selected publications:

1. "Saraswati: An Extremely Massive ~200 Megaparsec Scale Supercluster", J. Bagchi, S.
Sankhyayan, P. Sarkar, S. Raychaudhary, J. Jacob, P. Dabhade 2017, ApJ, 844, 25

2. "Discovery of giant radio galaxies from NVSS: radio and infrared properties", P. Dabhade, M. Gaikwad, J. Bagchi, M. Pandey-Pommier, S. Sankhyayan, S. Raychaudhury 2017, MNRAS, 469, 2886