Indian researchers discover a rare and farthest gamma-ray emitting galaxy

The researchers confirmed that the newly found farthest gamma-ray emitting NLS1 galaxy was formed when the Universe was only about 4.7 billion years old.

Created On: Apr 13, 2021 16:22 ISTModified On: Apr 13, 2021 17:10 IST
The spectrum of the farthest gamma-ray emitting Narrow-Line Seyfert 1 (NSL1) galaxy known till date, Image courtesy: ARIES, Nainital

Scientists from the Aryabhatta Research Institute of observational sciencES (ARIES), Nainital, an autonomous institute of the Department of Science & Technology (DST), Government of India, along with researchers from other institutions, have found the farthest gamma-ray emitting Narrow-Line Seyfert 1 (NSL1) galaxy known till date.

The researchers from ARIES in collaboration with researchers have been studying around 25,000 Active Galactic Nuclei (AGN) from the Sloan Digital Sky Survey (SDSS) and were able to devise a new method to find high-z NLS1 galaxies till now unknown by comparing different emission lines in their spectra. In the process, they found a high-z gamma-ray emitting NLS1 galaxy.

One of the largest ground-based telescopes in the world, the 8.2 m Subaru Telescope located in Hawaii, US was used to confirm the findings. Upon observation, researchers confirmed that they have found a genuine NLS1 galaxy at a high redshift of 1.34, which is about 31 billion light-years away from us.

The researchers confirmed that the newly found farthest gamma-ray emitting NLS1 galaxy was formed when the Universe was only about 4.7 billion years old. The current age of the Universe is 13.8 billion years.

The research was conducted by Dr. SuvenduRakshit of ARIES, Nainital in collaboration with various scientists Vaidehi S. Paliya (ARIES), C. S. Stalin (IIA, India), Indrani Pal (IIA, India), Malte Schramm (Japan), I. Tanaka (USA), Jaejin Shin (South Korea), and JariKotilainen (Finland).

The research will be published as a letter in the scientific journal Monthly Notices of the Royal Astronomical Society.

This research holds a promising potential for finding more gamma-ray emitting NSL1 galaxies and help understand the early Universe.

What are Active Galactic Nuclei (AGN)?

Most of the galaxies are powered by a supermassive black hole at their center. Normal black holes that form from the death of a single star are ten times the mass of the Sun, but the supermassive black holes are millions to billions of times the mass of the Sun.

These supermassive black holes found at the center of the galaxies are the reason that the compact region at the center of a galaxy has an extremely high luminosity. The bright central regions of these galaxies are called Active Galactic Nuclei (AGN). The galaxies hosting Active Galactic Nuclei (AGN) are called active galaxies.

Compared to normal galaxies, these active galaxies can emit up to thousands of times of energy. The emissions of active galaxies are non-stellar (non-thermal) that are observed in the form of microwave, radio, infrared, optical, X-ray, ultra-violet, and gamma-ray wavebands.

The gamma-ray emitting Narrow-Line Seyfert 1 (NSL1) galaxies

The Narrow-Line Seyfert 1 (NSL1) galaxies are classified as AGN. The type 1 Seyfert galaxies have narrow emission lines in their optical spectrum.

Earlier, the NSL1 galaxies were thought to be powered by low mass black holes and therefore were deemed very unlikely to produce relativistic jets. This was proved wrong when gamma-ray emissions were detected in them. Gamma-ray emissions areindicative of the presence of relativistic jets.

So far, dozens of NSL1 galaxies with redshifts lesser than one have been identified with gamma-ray emissions. But there was no method in place till now to find NSL1 galaxies with redshifts larger than one.

This changed when scientists from the Aryabhatta Research Institute of observational sciencES (ARIES), Nainital, an autonomous institute of the Department of Science & Technology (DST),found a genuine high-gamma ray emitting NLS1 galaxy at a high redshift of 1.34 (larger than 1).

What does a redshift or a redshifted galaxy mean?

Since Edwin Hubble in 1929 announced that the Universe is expanding, it was noted that the galaxies are moving away from us. The light, in form of wavelengths, from these receding galaxies is measured as redshift. This means farther the galaxies, the redder wavelengths of light and a larger redshift value. Such galaxies are classified as redshifted galaxies.

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