Study inspects large-scale turbulence in the galaxy NGC 6946

Indian astronomers have carried out a examine geared toward investigating a large-scale turbulence within the interstellar medium of a spiral galaxy generally known as NGC 6946. Outcomes of the examine, printed October 4 on the pre-print server arXiv, may assist us higher perceive the character of this phenomenon.

Observations present that the interstellar medium (ISM) is turbulent on scales as much as 1000’s of light years. This turbulence performs an vital position in a number of processes such because the formation of stars, the soundness of molecular clouds, and the re-acceleration and diffusion of cosmic rays. Nevertheless, though many research of turbulence in ISM have been carried out, its technology mechanism nonetheless baffles scientists.

NGC 6946 is a vivid late-type spiral galaxy situated some 19.2 million mild years away. It has an optical radius of round 32,000 mild years, dynamical mass of about 730 billion solar lots and a star-formation fee at a degree of two.5 solar masses per yr. Earlier observations of NGC 6946 have recognized the presence of a turbulence cascade within the disk of this galaxy.

Now, Meera Nandakumar and Prasun Dutta of the Indian Institute of Know-how (BHU) Varanasi, determined to take a better take a look at the turbulence in NGC 6946, by analyzing the information from the Karl G. Jansky Very Giant Array (VLA) and The HI Close by Galaxy Survey (THINGS). They used the visibility second estimator (VME) to measure the impartial atomic hydrogen (HI) column density and line of sight turbulent velocity energy spectrum from VLA and THINGS.

The outcomes level to the existence of a large-scale power cascade within the disk of NGC 6946. The examine discovered that the density energy spectrum of this galaxy has a slope of -1.81 and the column density slope was measured to be -0.96. Based on the authors of the paper, these findings counsel that the turbulence-driving mechanism for NGC 6946 comes from a mix of compressive and solenoidal forcing.

“The values of the ability legislation indices point out a mix of solenoidal and compressive drive liable for driving the measured turbulence,” the astronomers defined.

Furthermore, it was famous that NGC 6946 hosts inter-arm magnetic fields, generally known as magnetic arms with subject power of about 20 µG. Due to this fact, the researchers suppose that the magnetic field of NGC 6946 could have a significant position to drive the large-scale turbulence and these magnetic buildings are the results of turbulent dynamics within the disk.

The authors of the examine additional defined that the presence of sturdy common magnetic fields from the magnetic spiral arms in NGC 6946 is probably going contributing to the solenoidal half. They added that self-gravity or gravitational instability can principally be the enter for the compressive a part of the forcing within the driving mechanism.

Meera Nandakumar and Prasun Dutta plan extra research on the character of turbulence in ISM. They famous that measurements of the turbulence cascade on a lot of galaxies and decoding obtained outcomes with numerous numerical simulations is required as a way to advance our understanding of this phenomenon.

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