Professor Shen Juntai's team has made important progress in the study of the structure of the Andromeda Galaxy (M31)

Recently, the group of Professor Juntai Shen from the School of Physics and Astronomy of Shanghai Jiao Tong University has made important progress in the study of the structure of the Andromeda Galaxy (M31)

The research results were selected as a research highlight by the American Astronomical Society (AAS) Nova website on July 25, with a headline report on the website under the title "A Bar in the Andromeda Galaxy"

There are two types of spiral galaxies in the universe: normal spiral galaxies and barred spiral galaxies

Why do shock waves in interstellar gas serve as evidence for the existence of rods?

Previously, astronomers suggested that M31 may contain a galaxy bar based on the distortion of the stellar isoluminosity, but this phenomenon is not necessarily produced by a bar, but also by a non-rotating ellipsoid bulge

One of the most striking features of barred spiral galaxies is the formation of a pair of dust lanes on the leading side of the bar

Figure 1.

Based on this idea, the research team used the latest integrated field spectrometer VIRUS-W to observe the ionized oxygen gas emission line [OIII] in M31, combined with the neutral hydrogen atom gas (HI) data, and extracted the vertical direction to the galaxy disk.

The Andromeda Galaxy has a regular distribution of shock signatures

The research team found that these shock signatures are regularly distributed on a scale of the order of kiloparsecs (kpc)

Figure 2.

Comparison with numerical simulation of fluids

The research team found shock wave features mainly in the nuclear ball region of M31, with the strongest speed jump exceeding 170 km/s and a velocity gradient of 1.

Figure 3.

Feng Zixuan, a doctoral student at the Shanghai Astronomical Observatory of the Chinese Academy of Sciences, and Li Zhi, a postdoctoral fellow at the Department of Astronomy, Shanghai Jiao Tong University, are the co-first authors of the paper, and Professor Shen Juntai is the corresponding author

Paper link:

Feng, Z.

https://iopscience.

AAS Nova report link:

https://aasnova.