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arXiv · 2510.06668

Formation of A Nuclear Star Cluster Through A Merger Event In The Low Surface Brightness Galaxy AGC 223218

Tian-Wen Cao·Zi-Qi Chen·Zi-Jian Li·Cheng Cheng·Gaspar Galaz·Venu M. Kalari·Jun-feng Wang·Chun-Yi Zhang·Pei-Bin Chen·Meng-Ting Shen·Hong Wu
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Abstract

We present the properties of the nuclear star cluster (NSC) in the low surface brightness galaxy AGC 223218. The disk of the galaxy can be modeled using two S$\acute{\rm e}$rsic components with distinct central positions: one representing the inner bright disk and the other corresponding to the extended outer disk. We estimate the stellar masses of the NSC and the host galaxy using two methods: spectral energy distribution (SED) fitting and mass-to-light versus color relations (MLCRs). The stellar mass ratio of the NSC to AGC 223218 is 0.094 based on the SED method and 0.072 using MLCRs. The NSC presents a younger stellar population and a lower [Fe/H] value than the host, as determined from SDSS and LAMOST spectra analysis using pPXF fitting. AGC 223218 is located at the boundary between the Seyfert and star-forming regions in the [SII]-BPT diagram, whereas in the [NII]-BPT diagram, it falls in the track of star-forming SDSS galaxies. This suggests the presence of strong shocks in AGC 223218. We propose that the NSC in AGC 223218 may have formed as a result of a merger event. Furthermore, the observed X-ray luminosity of AGC 223218 with eROSITA is two orders of magnitude higher than the expected X-ray luminosity from X-ray binaries, suggesting the presence of an intermediate-mass black hole (IMBH) in the NSC. To account for the observed X-ray luminosity, we estimate the IMBH accretion rate to be approximately 0.001.

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Tian-Wen Cao, Zi-Qi Chen, Zi-Jian Li, Cheng Cheng, Gaspar Galaz, Venu M. Kalari, Jun-feng Wang, Chun-Yi Zhang, Pei-Bin Chen, Meng-Ting Shen, Hong Wu. 2025-10-08. Formation of A Nuclear Star Cluster Through A Merger Event In The Low Surface Brightness Galaxy AGC 223218. https://doi.org/10.3847/1538-4357%2Fadf559

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