A recent paper from a team of Canadian astronomers shows the intricate motion of gases surrounding a distant galaxy, NGC 1275. The team, all members of the Center for Research in Astrophysics of Quebec (CRAQ), included the paper’s lead author, Ph.D. student Marie-Lou Gendron-Marsolais, Julie Hlavacek-Larrondo from Université de Montréal, as well as Professor Laurent Drissen and Thomas Martin from Université Laval.
Located 250 million light-years from earth, NGC 1275 is an unusual galaxy. It sits in the middle of the Perseus galaxy cluster – a gigantic cluster harboring thousands of galaxies in the constellation of the same name.
Galaxy clusters are held together by gravity and contain not only galaxies as the name implies, but gas and stars between the galaxies. Surrounding many of the galaxies in a cluster is hot plasma containing hydrogen and helium. Astronomers call this plasma the intracluster gas or intercluster medium.
NGC 1275 is surrounded by hot, circulated intracluster gas with an average temperature of tens of millions of degrees — a gas that forms most of the luminous mass of galaxy clusters. Generally, astronomers use radio telescope to study the intracluster gas. However, a spectacular network of thin intricate filaments surrounding the galaxy NGC 1275 is visible at specific optical wavelengths.
“These types of filaments are often visible around galaxies that lie in similar environments … but their origin is a real mystery,” Marie-Lou Gendron-Marsolais declared.
Extending over 250,000 light-years, two and a half times the size of our own galaxy, the link connecting this large gas cloud to its environment is still very poorly understood because of the complex environments within clusters. Astronomers have two hypotheses but the ideas clash. First, the filaments could be condensing from the hot, intercluster gas and sinking towards the center of the galaxy. Or bubbles created by jets coming from the super massive black hole in the center of the galaxy lift the gas and drive it out of the galaxy.
To unravel the mystery of these filaments, the team decided to use SITELLE, an instrument at the Canada-France-Hawaii Telescope (CFHT) able to map the galaxy at several different wavelengths simultaneously. SITELLE is unique in that it images or takes a picture of the galaxy, then uses Fourier Transforms — a complex math function — to create a spectrum or rainbow for each pixel on the image. That’s a total of 4 million spectra in a SITELLE image.
Thanks to the instrument, the team could measure the radial velocity, namely the speed along the line of sight, of each of the filaments. By studying the speed, the team understands the motion or dynamics of the gas with an unequaled level of detail.
“It seems that the movement of this network of filaments is very complex; there does not seem to be any uniform movement, it is extremely chaotic,” Marie-Lou Gendron-Marsolais said.
The researchers are convinced that such observations can help to unravel the mystery of these structures. Overall, the understanding of the dynamics of these filaments is directly related to the processes of heating and cooling of the gas that feeds the central black hole. It therefore constitutes a key element in the study of galaxy evolution and, on a larger scale, environments such as clusters of galaxies.
The results of the research conducted by Marie-Lou Gendron-Marsolais, Hlavacek-Larrondo Julie, Laurent Drissen, Thomas Martin, as well as international collaborators, appear in a letter of the latest issue of the Monthly Notices of the Royal Astronomical Society. For a link to the article, check out the news section of CFHT’s webpage at www.cfht.hawaii.edu.
