Ruta Kale

Associate Professor G
Email: ruta [at]
Phone: +91 - 20 - 25719234
Extn: 9234
Office: F226
National Centre for Radio Astrophysics
Tata Institute of Fundamental Research
Savitribai Phule Pune University Campus,
Pune 411 007
Maharashtra, INDIA

Main Research Areas: Galaxy clusters: Cosmic rays and magnetic fields, Brightest Cluster Galaxies; Radio galaxies and their evolution.



Ruta obtained her B.Sc. in Physics from Mumbai University in 2003, and her M.Sc. in Physics, from the Indian Institute of Technology, Madras, in 2005. She then obtained her Ph.D. from the Jawaharlal Nehru University, New Delhi, in 2011, based on research work carried out at the Raman Research Institute, Bangalore. After a brief post-doctoral stint at the Inter-University Centre for Astronomy and Astrophysics, Pune, she spent 2.5 years as a Post-Doctoral Research Associate, jointly at the University of Bologna and the Institute of Radio Astronomy, Bologna, Italy. She joined NCRA as a Post-Doctoral Visiting Scientist in June 2014, and then took up a DST Inspire Faculty Fellowship at NCRA. She joined NCRA as a faculty member in October 2017.

Research description:

My research is aimed at understanding the physical mechanisms behind the generation and evolution of cosmic rays and magnetic fields on scales ranging from cluster cores to large scale structure.
Cluster mergers and cosmic ray acceleration
Diffuse radio emission termed as radio halos and relics are among the direct probes of the relativistic electrons and magnetic fields in galaxy clusters. Cluster mergers are closely linked to radio halos and relics but the precise conditions in a particular merger that leads to the generation of these sources is not well understood. A non-detection of such sources towards clusters is also useful to understand the physical conditions that can inhibit the formation of such sources. We are carrying out deep targeted observations of known radio halos and relics to understand the physics of particle acceleration in shocks and turbulence. A statistical study of these sources by surveying a large number of clusters across redshifts and masses is also being carried out.
Life cycle of radio galaxies in and around galaxy clusters
The Brightest Cluster Galaxies (BCGs) and their activity in radio bands are known to influence the physical conditions in cluster cores and are themselves also influenced by the dynamical state of the host cluster. The BCGs and other galaxies like head-tail galaxies in clusters are important sources that deposit relativistic particles in the intra-cluster medium. Studies in the last decade have shown that for the mechanisms of turbulent and shock acceleration to work efficiently, a seed relativistic population is required. Radio galaxies and their remnants can be important sources of the seed relativistic electron population. However the spectra of the seed population are not known well and are often assumed to be simple power-laws. In our work we are modeling spectra of radio galaxies and their remnants under different physical conditions and also obtaining precise broadband measurements of the same.
Non-thermal components of the cosmic web
The inter-galactic medium (IGM), that pervades the space between galaxies distributed across the cosmic web, is expected to be magnetised. In the process of large scale structure formation, shocks of Mach numbers reaching ~100 can be driven in the IGM and these can accelerate electrons to relativistic speeds. These energetic electrons and the weak magnetic fields will emit radiation by the synchrotron mechanism that can be detected in the radio frequency bands. This emission will be a direct tracer of the non-thermal components of the cosmic web. We are surveying potential sites for detecting the cosmic web using a variety of methods with radio telescopes like the uGMRT and MeerKAT.

Selected publications:

1. SoUthern Cluster sCale Extended Source Survey (SUCCESS): a GMRT and Meerkat study of nine massive galaxy clusters (R. Kale et al. 2022, MNRAS, 514, 5969).

2. Giant Metrewave Radio Telescope unveils steep-spectrum antique filaments in the galaxy cluster Abell 725 (M. Pandge, R. Kale, et al. 2022, MNRAS, 509, 1837)

3. Imaging results from the legacy Giant Metrewave Radio Telescope Galaxy Cluster Key Project (L. T. George, R. Kale, et al. 2021, MNRAS, 507, 4487)

4. Radio halos in a mass-selected sample of 75 galaxy clusters. II.  Statistical analysis (V. Cuciti et al., including R. Kale, 2021, A&A, 647, 51)

5. CAPTURE: a continuum imaging pipeline for the uGMRT (R. Kale & C. H. Ishwara-Chandra 2021, ExA, 51, 95)

6. A radio halo surrounding the Brightest Cluster Galaxy in RXCJ0232.2-4420: a mini-halo in transition? (R. Kale, K. M. Shende and V. Parekh, 2019, MNRAS Letters, 486, 80)

7. A study of spectral curvature in the radio relic in Abell 4038 using the uGMRT (R. Kale et al. 2018, MNRAS, 480, 5352)

8. Discovery of a radio relic in the low mass, merging galaxy cluster PLCK G200.9-28.2 (R. Kale et al. 2017, MNRAS, 472, 940)

9. Discovery of a fourth arc in Abell 2626 at 610 MHz with the GMRT: spectral properties and possibilities for the origin (R. Kale and M. Gitti, 2017, MNRAS Letters, 466, 19)

10. The Extended GMRT Radio Halo Survey. II. Further results and analysis of the full sample (R. Kale et al. 2015, A&A, 579, 92)