Breakthrough Discovery: Interaction of Radio Jet and Interstellar Gas in Dwarf Galaxy NGC 4395

In a groundbreaking study, scientists at the Indian Institute of Astrophysics (IIA), an autonomous institute of the Department of Science and Technology (DST), have revealed a significant interaction between a radio jet from a dwarf galaxy and the interstellar gas surrounding it, leading to the formation of shock waves.

The research focuses on the Active Galactic Nuclei (AGN) of the galaxy NGC 4395, where a black hole emits bright jets and winds that significantly influence the structure of their host galaxies. The team discovered that the radio jet, emitted from the AGN at the center of NGC 4395, interacted with the surrounding interstellar medium over a remarkably small spatial scale of approximately 30 light years. NGC 4395 itself is located about 14 million light years away from Earth.

The findings were published in the Astrophysical Journal, where the team utilized a comprehensive range of data, spanning from radio to X-ray wavelengths, to analyze the interactions occurring around the black hole. “We decided to investigate how the radio jet from a small black hole interacts with the gas in a dwarf galaxy called NGC 4395,” stated lead author Payel Nandi, a doctoral student at IIA.

To conduct this research, the team harnessed data from various advanced telescopes, including the UltraViolet Imaging Telescope (UVIT) on board AstroSat—India’s first dedicated space observatory launched by ISRO in 2015—as well as X-ray data from the Chandra X-ray Observatory and optical data from the Gemini-North and Hubble Space Telescopes.

The results revealed a unique radio structure resembling a bipolar jet, with its core precisely centered on the black hole. “This jet is relatively weak, but our multi-wavelength analysis of this 30-light-year region showed that the jet is interacting with the surrounding gas, and possibly causing shock waves to propagate through it,” explained Prof. C. S. Stalin, a co-author of the study.

The emitted light from ionized oxygen in the optical band, molecular hydrogen in the infrared, and X-ray emissions closely followed the path of the radio jet. Nandi highlighted that the study provides “strong evidence for an outflow of material carried by the jet into the surrounding medium.”

This pioneering research not only enhances our understanding of black holes and their effects on nearby cosmic structures but also marks a significant milestone in astrophysics, showcasing the capabilities of Indian scientific institutions in contributing to global knowledge in the field.