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Part of the book series: Springer Theses ((Springer Theses))

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Abstract

The aims of this first chapter are to provide: (1) a short history of the discovery of galaxies and AGN; (2) a summary of the key properties and observations of AGN, which are thereafter referred to throughout this thesis; (3) a brief review of the current research on the influence of active galactic nuclei on the evolution of galaxies. Introductory material, specific to the topic being investigated, is also provided at the beginning of individual science chapters.

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Notes

  1. 1.

    The lines typically used were the permitted line H\(\beta \) and the forbidden line [O iii]\(\lambda \)5007. Further discussion on emission lines in AGN is provided in Sect. 1.2.3 and Appendix A.

  2. 2.

    It is now common practice to use the term “quasar” to refer to the most luminous AGN in the Universe (i.e., bolometric luminosities of \(L_{\mathrm{AGN}}\gtrsim 10^{45}\) erg s\(^{-1}\); see Sect. 1.2.4), irrespective of their radio properties. Throughout this thesis the term quasar is used as a generic term to refer to very luminous AGN.

  3. 3.

    Throughout this thesis only “supermassive” black holes are referred to; i.e., those with a mass in the range \({\approx }10^{5}\)\(10^{10}\,\mathrm{M}_{\odot }\). This is in contrast to stellar mass BHs that have masses \({\approx }2\)\(20\,\mathrm{M}_{\odot }\) (e.g., McClintock and Remillard 2006).

  4. 4.

    There are multiple definitions of “radio-quiet” AGN (as opposed to radio-loud AGN) used throughout the literature and it is therefore useful to clarify this term here. Historically, radio-loud AGN are defined as those where the ratio of 5 GHz radio luminosity (\(L_{\nu }\)[5 GHz]) to B-band optical luminosity (\(L_{\nu }\)[B]) is much higher than average (i.e., \(L_{\nu }\)[5 GHz]/\(L_{\nu }\)[B] \(>10\); Kellermann et al. 1989; also see Xu et al. 1999 for a definition using optical emission lines). The term “radio loud” is also sometimes used interchangeably with “radio AGN” where AGN dominate the radio emission over star formation (see Best and Heckman 2012 and references there-in). Additionally, “radio loud” is often used as a generic term to describe AGN that are particularly luminous at radio wavelengths (e.g., \(L_{\mathrm{1.4\,GHz}}\gtrsim 10^{25}\) W Hz\(^{-1}\)). In this thesis, “radio loud” is used to refer to sources with exceptionally high radio luminosities where the luminosity is almost certainly dominated by the AGN and “radio quiet” refers to more typical radio luminosities of \(L_{\mathrm{1.4\,GHz}}\lesssim 10^{24-25}\) W Hz\(^{-1}\). The term “high-excitation” (opposite to “low-excitation”) radio AGN is used to refer to radio-identified AGN that also look like AGN based on various optical emission-line diagnostics (see Best and Heckman 2012 and references there-in; also see Sect. 1.3.5). Finally, “radio excess” AGN are defined as AGN where there is significant radio emission above that expected from star formation alone (e.g., Roy and Norris 1997; Donley et al. 2005; Del Moro et al. 2013) that could imply radio emission from an AGN.

  5. 5.

    The assumption of an optically thick accretion disk may only be valid for radiatively-efficient AGN that are the focus of this thesis (see e.g., Yuan and Narayan 2014; Heckman and Best 2014 and references there-in).

  6. 6.

    It should be noted that in a fraction of radio-loud AGN the mid-IR emission may have a significant non-thermal contribution (e.g., Dicken et al. 2008).

  7. 7.

    Measuring a bulge mass is notoriously more difficult than measuring their luminosity. Whilst it should be possible to convert between luminosity and mass in bulges (as the stars dominate both the mass and the luminosity), the appropriate choice of conversion is not trivial (see Kormendy and Ho 2013 for a discussion of this in relation to BH–bulge mass relationships).

  8. 8.

    It has also been suggested that the \(M_{\mathrm{BH}}\)\(M_{\mathrm{bulge}}\) relationship may be a natural consequence of repeated mergers (e.g., Peng 2007; Jahnke and Macciò 2011).

  9. 9.

    The binding energy of \(E_{\mathrm{BE}} \approx 10^{58}\) erg is obtained assuming \(M_{\mathrm{bulge}} = 3\times 10^{10}\,\mathrm{M}_{\odot }\) (following Eq. 1.4.6) and \(E_{\mathrm{BE}} \approx M_{\mathrm{bulge}}\sigma ^2\) with \(\sigma \approx 200\) km s\(^{-1}\).

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Correspondence to Christopher Mark Harrison .

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Harrison, C.M. (2016). Introduction. In: Observational Constraints on the Influence of Active Galactic Nuclei on the Evolution of Galaxies. Springer Theses. Springer, Cham. https://doi.org/10.1007/978-3-319-28454-5_1

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