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Spin flips show how galaxies grow from the cosmic web
Examples of SAMI galaxies with central bulge and surrounding disc. Credit: Hyper Supreme-Cam Subaru and Pan-STARSS

The processes by which different components of the universe form are revealed by the alignment between the galaxy spins and the large-scale structure.

The structure of the universe is determined by the distribution of galaxies. The "cosmic web" is a collection of giant structures.

According to a new study published in Monthly Notices of the Royal Astronomical Society, larger bulges tend to spin parallel to the filaments in which they are embedded, while smaller bulges tend to spin in a different direction.

Dr. Barsanti is a member of the ASTRO 3D Centre of excellence and is the lead author of the paper.

Galaxies with a low-mass bulge tend to have their spin axis parallel to the nearest one. They are formed from gas falling onto the filaments and rolling it up. The bulges grow when the galaxies merge. Mergers tend to flip the alignment between the galaxy spin and the Filament.

As the galaxies move towards each other, we believe that mergers will be more likely. The spin flip is caused by the direction of the mergers.

The discovery sheds light on the formation of two main components of galaxies and how they relate to the large-scale structures and motions of matter in the Cosmic Web.

The motivation was to understand why galaxies spin and how they acquire their spin from the material that forms them.

She says that the study can show how mergers play an important role in the formation of galaxies. The formation channels for how galaxies spin and how they evolve are shown.

This study is the first time scientists have used direct observation to confirm the growth of a central bulge can cause it to flip alignments.

The signals are hard to detect in the observations.

It has been possible with the advent of integral field spectroscopy, a technique in which an optical instrument combines spectrographic and imaging capabilities to build a 3D image of a galaxies and at the same time resolve its internal motions.

The SAMI was attached to the telescope in New South Wales.

SAMI was used by researchers to survey more than 3000 objects. The amount of data has taken a long time to study and provide evidence for a paper.

Dr. Barsanti says that with the SAMIGalaxy Survey we can map the galaxy with the help of spatial resolution. The internal motions of the stars and gas within the universe can be measured. The next stage of our research will be the results of these tests. We'll use the Anglo-Australian Telescope to survey around 30,000 galaxies with the next- generation spectrograph, called "HECTOR".

Professor Wy says that the paper shows how the motions of mass in galaxies and their positions are connected, which is an important piece in understanding how galaxies assembled.

The study was done in collaboration with researchers from a number of universities.

More information: Stefania Barsanti et al, The SAMI Galaxy Survey: flipping of the spin-filament alignment correlates most strongly with growth of the bulge, Monthly Notices of the Royal Astronomical Society (2022). DOI: 10.1093/mnras/stac2405 Journal information: Monthly Notices of the Royal Astronomical Society Provided by ARC Centre of Excellence for All Sky Astrophysics in 3D (ASTRO 3D)