Book contents
- Frontmatter
- Contents
- Preface
- 1 Observations of active galactic nuclei
- 2 Nonthermal radiation processes
- 3 Black holes
- 4 Accretion disks
- 5 Physical processes in AGN gas and dust
- 6 The AGN family
- 7 Main components of AGNs
- 8 Host galaxies of AGNs
- 9 Formation and evolution of AGNs
- 10 Outstanding questions
- References
- Index
- Plate section
10 - Outstanding questions
Published online by Cambridge University Press: 05 June 2013
- Frontmatter
- Contents
- Preface
- 1 Observations of active galactic nuclei
- 2 Nonthermal radiation processes
- 3 Black holes
- 4 Accretion disks
- 5 Physical processes in AGN gas and dust
- 6 The AGN family
- 7 Main components of AGNs
- 8 Host galaxies of AGNs
- 9 Formation and evolution of AGNs
- 10 Outstanding questions
- References
- Index
- Plate section
Summary
Of the many questions addressed in this book, some are still open and require more attention. Answering these questions will lead to a much improved understanding of active and dormant BHs, of the physics in the various regions of AGNs, and of the complex evolutionary connections between massive BHs and their host galaxies. The questions that are considered to be more important are arranged subsequently in four large categories. Most of these issues were discussed in the previous chapters, and the list is only intended to serve as a reminder of the outstanding questions in this area of research and of the direction in which the field is going.
Questions related to the central power house
Black hole mass and spin
BH mass measurements in local type-II AGNs are based on the M–σ* relationship and the known relationships between bulge luminosity and BH size. For type-I AGNs, the estimates are based on RM-based measurements of RBLR and the assumption of virialized BLRs. As of 2011, Hβ-based RBLR estimates are available for about 40 sources, and it is not at all clear how well this sample represents the various types of AGNs, for example, radio loud versus radio quiet, high versus low luminosity, and high versus low L/LEdd. The large, yet limited range of Lbol requires extrapolation to reach the highest-luminosity AGNs. This limits the accuracy of BH mass estimates in the most luminous AGNs.
- Type
- Chapter
- Information
- The Physics and Evolution of Active Galactic Nuclei , pp. 330 - 338Publisher: Cambridge University PressPrint publication year: 2013