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Dark matter distribution in galaxies is a key to test the LCDM and galaxy formation models. We measure the dark-matter mass distribution for a representative sample of 140 nearby galaxies by combining IFU data from MaNGA and HI spectra from FAST. We find strong evidence that these galaxies exhibit a lower dark-matter densities in their inner regions than predicted by cosmological simulations in the framework of CDM as well as alternative dark matter models in AIDA-TNG. Compared to these simulations, our galaxies have a dark-matter deficit core, with the core size increasing from about 10 kpc to 50 kpc for galaxies with stellar masses ranging from 5e9 to 3e11 M⊙. Although it is not entirely clear how these DM-deficit regions form, evidence is clearly seen in our observational results. In the case of the MW, we find a similar dark-matter deficit core; more interestingly, we have managed to precisely determine the 3D shape of its dark-matter halo. Unexpectedly, the MW dark-matter halo is vertical to the stellar disc and in alignment with the prominent satellite plane. Such striking configuration is rare but not an outlier in the cosmological simulations, they suggests a flip of the Galactic disc caused by minor mergers.

BIO

I have led a research group on galactic dynamics in Shanghai Astronomical Observatory (中国科学院上海天文台) since 09/2018. Before joining SHAO, I was a postdoc researcher at the Max Planck Institute for Astronomy, Heidelberg, Germany (德国马普天文所) from 2013-2018. I got my Ph.D. degree at the Center for Astrophysics, Tsinghua University (清华大学天体物理中心) in 2013. I obtained my Bachelor's degree from Department of Physics, Tsinghua University, Beijing (清华大学物理系) in 2008.

Host: Dandan Xu