Shulou(Shulou.com)12/24 Report--

CTOnews.com, December 9 (Xinhua)-- the National Astronomical Observatory of the Chinese Academy of Sciences recently released scientific research developments, saying that Xu Jinlong and other researchers using FAST neutral hydrogen observation data have brought new insights into how massive lens galaxies are formed.

The team looked at a massive lens galaxy in a neighboring galaxy group and found that it was a new way of morphological transformation formed by a late-type spiral galaxy under the tidal action of a group of dwarf galaxies.

The team also discovered for the first time an optical bright-dark galaxy pair whose companion galaxy may be a newly formed protogalaxy, which will also bring a new perspective to the field of galaxy formation.

How different types of galaxies are formed is an important question in astrophysics. Lens galaxies (S0), located between early-type elliptical galaxies and late-type spiral galaxies in the Hubble taxonomic sequence, consist of a central nuclear ball and a star disk without spiral arms, most of which lack gas.

At present, it is generally believed in observation and numerical simulation that lens galaxies are formed by a spiral galaxy through the environmental stripping mechanism or by the merger of two spiral galaxies.

The team analyzed the interaction of the lenticular galaxy with four dwarf galaxies by using highly sensitive and high spectral resolution FAST to observe the neutral hydrogen (HI) of NGC 1023 (figure 1).

Figure 1. Neutral hydrogen radiation map of S0 galaxy NGC 1023. The small image on the upper right shows its optical DSS-B band radiation map. In particular, it is found that one of the largest dwarf galaxies has fallen into the gas disk of NGC 1023, forming a rare bright-dark galaxy pair with a mass of gas in the disk and triggering the formation of young star clusters (figure 2).

Figure 2. Bright-dark galaxies. Yeah. The bright galaxy in the optical band is NGC 1023A, while the dark galaxy is NGC 1023E. Among them, the green circle and red circle represent the formed young star clusters, whose age is about 100 Myr. This massive gas mass has been found to have the same physical and dynamic characteristics as dwarf galaxies, but there are no optical counterparts, indicating that it may be a newly formed protogalaxy.

Finally, through the dynamic analysis of optical and other multi-band data, it is shown that NGC 1023 is formed by morphological transformation under the tidal action of a group of dwarf galaxies.

A reference link to the paper is attached to CTOnews.com: https://iopscience.iop.org/article/10.3847/2041-8213/ad0cf5.

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