# Detection of the Low-Stellar Mass Host Galaxy of a $z\sim6.25$ quasar with JWST

**Authors:** Meredith Stone, Jianwei Lyu, George H. Rieke, Stacey Alberts  
**arXiv:** [2308.00047](https://arxiv.org/abs/2308.00047)  
**Date:** 2023-07-31  
**Summary page:** https://www.summarizepaper.com/en/paper/2308.00047v1/

## Key points

- Study investigates stellar mass and black hole mass of J2239+0207, a sub-Eddington quasar at redshift z~6.25
- Utilizes medium-band observations from JWST's NIRCam to determine the stellar mass, estimating it to be approximately 10^10 solar masses
- Stellar mass is more than an order of magnitude lower than previously measured dynamical mass based on [C II] line widths
- Black hole mass calculated using JWST's NIRSpec IFU observations, found to be approximately 15 times more massive than predicted by local M_BH-M* relation
- Comparison of z~6 quasars to local sample shows many high-redshift quasars have overmassive black holes compared to their stellar masses
- Study provides insights into properties of a z~6.25 sub-Eddington quasar and emphasizes the need to consider its unique evolution in studying black hole-galaxy coevolution

## Summary

In this study, the authors investigate the stellar mass and black hole mass of J2239+0207, a sub-Eddington quasar at redshift z~6.25 using dedicated observations from the James Webb Space Telescope (JWST). To determine the stellar mass of J2239+0207, they utilize medium-band observations from JWST's Near Infrared Camera (NIRCam) to reveal the underlying galaxy emission of J2239+0207. This leads to an estimated stellar mass of approximately 10^10 solar masses which is more than an order of magnitude lower than the previously measured dynamical mass based on [C II] line widths. Additionally, they calculate the black hole mass using JWST's Near Infrared Spectrograph (NIRSpec) Integral Field Unit (IFU) observations and find that it is approximately 15 times more massive than predicted by the local M_BH-M* relation between black hole and stellar masses. The authors compare z~6 quasars to a local sample with similarly determined dynamical masses and find that many high-redshift quasars exhibit overmassive black holes compared to their stellar masses. This study provides valuable insights into the properties of a z~6.25 sub-Eddington quasar and highlights the need to consider its unique evolution when studying its black hole-galaxy coevolution.