# The Co-Evolution of Galaxies and Supermassive Black Holes: Insights from Surveys of the Contemporary Universe

**Authors:** Timothy Heckman, Philip Best  
**arXiv:** [1403.4620](https://arxiv.org/abs/1403.4620)  
**Date:** 2014-03-18  
**Summary page:** https://www.summarizepaper.com/en/paper/1403.4620v1/

## Key points

- Timothy Heckman and Philip Best conducted a comprehensive review on the relationship between galaxies and supermassive black holes.
- Two distinct populations of active galactic nuclei (AGN) were identified based on their modes of operation: Radiative-Mode AGN and Jet-Mode AGN.
- Radiative-Mode AGN are associated with less massive black holes evolving within high-density pseudo-bulges, emitting radiant energy through accretion processes exceeding 1% of the Eddington Limit.
- Circum-nuclear environments surrounding Radiative-Mode AGN are rich in high-density cold gas, fostering significant levels of star formation primarily driven by secular mechanisms rather than major mergers.
- Jet-Mode AGN are linked to more massive black holes situated within classical bulges and elliptical galaxies, with energetic output manifesting as collimated outflows or jets.
- Accretion onto Jet-Mode black holes and star formation within their host bulge are relatively insignificant compared to Radiative-Mode counterparts due to slowly cooling hot gas accretion processes regulated by feedback mechanisms driven by AGN radio sources.

## Summary

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In their comprehensive review, Timothy Heckman and Philip Best delve into the intricate relationship between galaxies and supermassive black holes, drawing insights from extensive surveys of the contemporary universe. Through their analysis, they identify two distinct populations of active galactic nuclei (AGN) based on their modes of operation. The first group, known as Radiative-Mode AGN, is characterized by black holes that emit radiant energy through accretion processes exceeding approximately 1% of the Eddington Limit. These AGN are typically associated with less massive black holes evolving within high-density pseudo-bulges at a rate sufficient to account for their total mass accumulation over a span of around 10 billion years. The circum-nuclear environment surrounding these AGN is rich in high-density cold gas, fostering significant levels of star formation. Contrary to common belief, major mergers do not play a primary role in funneling gas towards the central regions; instead, secular mechanisms appear to dominate this process. Additionally, these AGN exhibit generic stellar feedback effects, with strong AGN feedback observed only in the most powerful instances. On the other hand, Jet-Mode AGN represent a distinct category where the majority of energetic output manifests as collimated outflows or jets. These AGN are typically linked to more massive black holes situated within classical bulges and elliptical galaxies. Unlike Radiative-Mode counterparts, accretion onto these black holes and star formation within their host bulge are relatively insignificant in present-day observations. The fuel source for Jet-Mode AGN is believed to stem from slowly cooling hot gas accretion processes regulated by feedback mechanisms driven by AGN radio sources. Furthermore, surveys conducted on high-redshift regions of the universe mirror these findings, reinforcing the notion that distinct populations of AGN exist based on their operational modes and host galaxy characteristics. By elucidating these relationships between galaxies and supermassive black holes across different cosmic epochs, Heckman and Best provide valuable insights into the co-evolutionary processes shaping our understanding of galactic dynamics and cosmic evolution as a whole.