Galaxy Evolution
Bulges of Galaxies
Studies of spirals, ellipticals, and lenticulars (ApJ Letter, MNRAS paper). Related work explored bar fraction in lenticulars as a function of luminosity and environment.
We reported systematic differences in the star formation history of bright and faint lenticular galaxies. My short review article summarises early work in this area.
Recent papers cover: pseudo bulge fraction vs environment, S0s in high density environments, age bimodality in pseudo bulges, why classical bulges are more common in lenticulars, and spectral study of pseudobulges using SALT.
Star-formation in and around Galaxies
Used WFPC2 parallels of the Hubble Ultra Deep Field to study star-forming galaxies at z < 2 and Lyman break galaxies at higher redshifts (AAS Poster, AJ paper). We investigated the importance of morphological K correction in UV bright galaxies.
For blue cloud galaxies (0 < z < 1), we studied the radio-FIR correlation and the dependence of star formation on morphology and environment.
Related studies: outlying H-alpha emitters, discovery of a giant hydrogen ring, star-forming S0 galaxies in SDSS-MaNGA, structure and kinematics of star-forming ellipticals, and low-metallicity warm plasma discovery with HST/COS.
Low-surface Brightness Features
We serendipitously discovered a galaxy with the longest known tidal tail.
High Redshift Galaxies
We discovered the highest redshift spiral galaxy known using JWST data.
Radio Properties of Galaxies
Radio Continuum Emission from AGN
For my doctoral thesis, I studied radio emission from Quasars. A companion paper discussed radio emission from Seyfert galaxies. My thesis was titled "Optical studies of VLA FIRST Survey radio sources" (PDF).
Follow-up work includes: GMRT observations of an AGN cum luminous type IIn supernova, kiloparsec-scale radio emission in Seyfert and LINER galaxies, discovery of rare double lobed radio AGN in spiral galaxies.
Giant radio galaxy discoveries: relic giant at z~1.3, giant at z~0.57, and double-double radio galaxies. Remnant radio galaxy studies: Lockman Hole field, overview paper, new XMM-LSS remnants, small angular size remnants.
Galaxy Clusters
Developed an upper limit calculator for extended cluster radio haloes. Used GMRT archival observations to detect and characterise radio haloes in 39 galaxy clusters.
Nearby Spirals
Studied radio continuum emission of 6 nearby spirals to constrain cosmic ray electron generation, diffusion, and energy losses at ~1 kpc scales.
High Redshift Radio Galaxies
Deep GMRT observations to identify high redshift radio sources using the steep spectrum technique. Combined with optical/IR data to characterise steep spectrum sources. Discoveries include relic high-z giant radio galaxy and another high-z giant. Studies of Infrared Faint Radio Sources and dust obscured radio-AGN.
Software and Technology Development
Square Kilometre Array (SKA)
Since 2010, part of the NCRA group working on SKA related activities. Focused on the Monitoring and Control System. URSI 2011 paper and concept design documents (zip) describe our work. Technologies developed were implemented in the GMRT monitoring and control system.
Recent: SPIE paper, 2023 overview. For S20 policy webinar on Astroinformatics, led a panel on Large projects in Astronomy. Member of SKA-India continuum science group (science interests paper).
SKA Regional Centre
Member of the SKA Regional Centre Steering Committee, coordinating efforts to build a regional centre in India. Contributing to SRCNet documents and overview paper.
Astronomy Software
Developed fitgal (bulge-disk decomposition), PyMorph (GitHub) for galaxy morphology, APPP data processing, telescope scheduler, and NAPS (NCRA Archive & Proposal System).
Machine Learning in Astronomy
Worked on star-galaxy classification using Difference Boosting Neural Network (DBNN), used to classify SDSS DR7 detections. Proposed new approach to photometric redshift estimation, and more recently developed a scaled ensemble framework for photo-z estimation up to z~4.
Deep learning applications: predicting star formation properties, bulge-to-total ratio, and radio galaxy morphological classification. Contributed to ASI Vision Document chapter on AI/ML in Astronomy.