New Insights into Black Hole and Galaxy Assembly in Boötes

Recent research conducted in the Boötes field has provided new insights into the assembly of black holes and their host galaxies. The study, titled "X-ray AGN in Boötes: Black Hole - Galaxy assembly in massive populations," was authored by Paloma Guetzoyan and six others. It utilized data from the Chandra Deep-Wide Field Survey (CDFWS) to analyze black hole-galaxy assembly in massive galaxies with stellar masses exceeding 10 billion solar masses.

The researchers measured the active galactic nucleus (AGN) fraction and specific black hole accretion rate (sBHAR) distribution as functions of redshift and stellar mass. They determined stellar masses and star formation rates for a sample of optically selected galaxies, including those with X-ray detections indicating AGN presence through spectral energy distribution fitting.

Key findings include:

• A redshift-dependent mass completeness limit was established, allowing for a comprehensive understanding of the AGN population in massive galaxies across different redshifts.
• The study found that while X-ray AGN samples are predominantly from moderately massive host galaxies, there is no strong dependence of AGN fraction or sBHAR distribution on stellar mass above the 10 billion solar mass threshold.
• A slight increase in AGN fraction was observed towards higher stellar masses for low sBHAR AGN, while high sBHAR events were suppressed in the most massive galaxies.
• The research revealed that most black hole mass accumulation occurred since redshift 4 for lower mass black holes, whereas the assembly of the most massive black holes is more complex, indicating that rapid growth episodes prior to redshift 4 were crucial for their formation.

These findings contribute to the understanding of the relationship between black holes and their host galaxies, particularly in the context of massive populations. The full study can be accessed at arXiv:2408.14297.