Scientists discover farthest gamma-ray emitting galaxy

Largest telescopes used for research

For the research, scientists used one of the largest ground-based telescopes in the world, the 8.2 m Subaru Telescope located at Hawaii, USA.

They helped establish a new method to find high red-shift NLS1 galaxies that were not known previously by comparing different emission lines in their spectra.

The new gamma-ray emitting NLS1 was formed when the universe was only about 4.7 billion years old as compared to its current age of about 13.8 billion years.

Vijay Mohan

Tribune News Service

Chandigarh, April 13

Astronomers have discovered a new active galaxy identified as the farthest gamma-ray emitting galaxy. The active galaxy — Narrow-Line Seyfert 1 (NLS1) — which is about 31 billion light-years away, opens up avenues to explore more such gamma-ray emitting galaxies.

Ever since 1929 when Edwin Hubble discovered that the universe is expanding, it has been known that most other galaxies are moving away from us. Light from these galaxies is shifted to longer wavelengths. As wavelength gets longer, the hue of light turns more red and is termed as ‘red-shifted’. Scientists have been trying to trace such red-shifted galaxies to understand the early Universe.

Scientists from Aryabhatta Research Institute of Observational Sciences (ARIES), Nanital, in collaboration with researchers from other institutions, studied around 25,000 luminous Active Galactic Nuclei (AGN) and found a unique object that emits high-energy gamma rays located at a high red-shift.

They identified it as a gamma-ray emitting NLS1 galaxy, which is a rare entity in space. The Sloan Digital Sky Survey (SDSS), a major optical imaging and spectroscopic survey of astronomical objects that has been in operation for the last 20 years, was used for the study.

As of today, gamma-ray emission has been detected in about a dozen NLS1 galaxies, which are a separate class of AGN identified four decades ago. All of them are at lower red-shifts, and no method was available till date to find NLS1 at higher red-shifts. This opens up a new way to find gamma-ray emitting NLS1 galaxies in the early Universe.

The research was led by Dr Suvendu Rakshit from ARIES, Other in the team included CS Stalin, Vaidehi S Paliya and Indrani Pal from India, Malte Schramm from Japan, I Tanaka from USA, Jari Kotilainen from Finland and Jaejin Shin from South Korea.