New research using the MeerKAT radio telescope in South Africa reveals the age of plasma in massive jets and dynamical processes in giant radio galaxies
A new study by an international team of researchers from South Africa, the United Kingdom, Spain and China, which was recently published, provides fascinating insights into giant radio galaxies (Giant Radio Galaxies - GRGs) through detailed spectral analysis of radio observations at different frequencies. These galaxies, which are considered the largest structures in the observable universe, include huge jets of radioactive plasma that extend over hundreds of thousands to millions of kilometers.
The study focused on three giant radio galaxies found in the cosmos field: MGTC J095959.63+024608.6, MGTC J100016.84+015133.0, and MGTC J100022.85+031520.4. The last of which was identified for the first time as part of this study. Each of these galaxies presents unique and important features for understanding the processes of formation and development of galaxies and the intergalactic environment.
What are giant radio galaxies, and why are they important?
Giant radio galaxies are defined by their enormous size, exceeding 700 kiloparsecs (kpc), and they include jets of plasma ejected from the galactic nucleus. These jets result from the activity of a supermassive black hole in the galactic core, which emits extremely strong radioactive radiation. This phenomenon, known as "jet feedback", may affect the intergalactic environment and prevent the formation of new stars by heating the gas in the environment.
The study of giant radio galaxies can provide insights into cosmic-scale processes, such as galaxy evolution, intergalactic interactions, and the effect of nuclear activity on the interstellar and intergalactic environment.
The researchers used the MeerKAT radio telescope, located in South Africa, to make observations at different frequencies ranging from 544 MHz to 1.67 GHz. Spectral analysis of these observations made it possible to map the age of the plasma in the jets of each of the galaxies.
One of the galaxies studied, MGTC J100022.85+031520.4 (referred to as GRG3), is a new galaxy identified for the first time in this study. It is a giant radio galaxy about 4.1 light-years long, located in the center of a sparse galaxy cluster. The identification of this galaxy contributes to the understanding of the relationship between large galactic structures and their surroundings.
The study is based on two methods for spectral age analysis: the Jaffe-Perola model and the Tribble model. These models describe the aging of plasma by measuring radiation at different frequencies. The results show that the GRG1 and GRG2 galaxies have a typical age distribution, with the youngest plasma located in the core, while the oldest plasma is located in the outer arms.
The difference between spectral age and dynamic age
During the research, a significant gap between spectral age and dynamic age was discovered. For example, the spectral age of GRG3 is about 67 million years, while its dynamic age, calculated from the size and strength of the jets, may reach up to about 950 million years. This gap highlights the need for more advanced physical models to understand dynamical processes in galaxies.
Conclusions and implications
1. The effect of the environment: giant radio galaxies like GRG3, which are in a denser environment, show a different age distribution than those found in isolated environments. This indicates that the density of the environment may play an important role in the formation of galactic structures.
2. Model Gaps: The study highlights the differences between spectral and dynamical models, and suggests that there are additional processes that are not included in current models, such as adiabatic energy loss and mixing of plasma with different energy levels.
3. Importance of technology: The study illustrates the advantages of the MeerKAT radio telescope, which enables the detection of previously unseen weak and diffuse radio structures.
This research is a significant step in understanding the physical mechanisms of giant radio galaxies and their effect on their environment. The discoveries not only contribute to the understanding of the universe, but also open the door to future studies using advanced technologies for radio-astronomical analysis.
