Análisis de la partícula rü en el corpus obtenido

are the best-fit model, and the data points are calculated from either the soft or hard band sample. Note that the number density of luminous AGN peaks at higher redshifts that lower-luminosity AGN (i.e., AGN cosmic downsizing). Bottom: Comoving mass density of all SMBHs plotted against red shift (uppermost solid curve, black). Note the shift of the peak for AGNs withLBol < 1045erg s−1 (orLX < 1043erg s−1). Taken fromUeda et al.(2014).

1043_{− 10}44_{erg s}−1 _{dominate at lower redshifts. Fig.1.5 shows that the luminosity depen-}

dence of AGN evolution results in a shift of the SMBH mass density peak from _{z ∼ 2,} where AGNs with LBol = 1046 − 1047 erg s−1 (or LX = 1044 − 1045 erg s−1) make the

largest contribution, to lower redshifts (Ueda et al., 2014). Approximately, the integrated fractions of SMBH growth at_{z < 1, z = 1 − 2, and z > 2 are 35 − 50 per cent, 25 − 40 per} cent, and_{15 − 25 per cent, respectively (e.g.}Marconi et al., 2004;Silverman et al., 2008a; Aird et al., 2010; Ueda et al., 2014). Two important AGN sub-populations for the growth of BHs and galaxies are optically selected quasars which contribute about _{≈ 40 − 50 per} cent (e.g. Di Matteo et al., 2003) to the integrated fractions of SMBH growth representing a rapid growth phase of massive BHs and, RLAGNs which contribute< 10 per cent (e.g. Cattaneo & Best, 2009) but appear to have played a significant role in the formation and evolution of galaxies.

Although RLAGNs are a minority at all redshifts, the large amount of kinetic/mechani- cal energy produced by the jets and lobes can be transferred to the host galaxy or large-scale environment and prevent the gas cooling and star formation. Therefore, the radio luminosity functions associated with AGN activity are used to observationally constraint the volume- average heating rate from AGN (e.g.Croton et al.,2006;Lehmer et al.,2007;Smolˇci´c et al., 2009; La Franca et al., 2010). Obtaining an estimate of the mechanical radio power has proven to be a difficult problem with a basic requirement of converting the synchrotron jet luminosity into a kinetic energy (e.g.Best et al., 2006;Heinz et al., 2007;Cavagnolo et al., 2010). On the basis of the current conversion factors, the kinetic energy density is pre- dicted to be broadly flat over _{z ≈ 0 − 4, with power density being completely dominated} by low luminosity AGN at low redshifts, while the contribution from RLQs becomes sig- nificant at _{z ∼ 2 (e.g.} Merloni & Heinz, 2008; Cattaneo & Best, 2009). There is evidence for a sharp (about a factor of five) decrease of the kinetic energy density atz < 0.5, which would indicate a weakening role of AGN activity towards_{z ≈ 0 (e.g.}K¨ording et al., 2008; La Franca et al.,2010).

1.5

The host galaxies of distant AGNs

In the past 20 years astronomers discovered that almost every massive galaxy hosts a cen- tral galactic BH (MBH ≈ 105 − 1010 M⊙). The existence of SMBHs at the center of

massive nearby galaxies has been confirmed mostly from the dynamics of stars and gas kinematics (e.g. Kormendy & Richstone, 1995). In the case of AGN, it has been possi- ble to measure SMBH masses due to a technique known as reverberation mapping (e.g. Blandford & McKee,1982;Peterson,1993) which provides indirect BH mass estimates and kinematic studies which are known to provide the most reliable mass measurements (e.g. Kaspi et al., 2000). These measurements have lead astronomers to establish well-defined black hole mass scaling relations with host galaxy properties such as: stellar mass in the

spheroidal component (e.g.Marconi & Hunt,2003), luminosity (e.g.Magorrian et al.,1998), velocity dispersion (e.g.Gebhardt et al.,2000b;Ferrarese & Merritt,2000;McConnell & Ma, 2013) and mass of the dark matter halo (e.g.Ferrarese,2002). The tightness of these relations suggests there may be a link between black hole formation and galaxy evolution.

Researchers, trying to understand the origin of this BH-spheroid mass link, have re- vealed the need of the presence of powerful phenomena such as gas-rich major mergers (e.g. Sanders & Mirabel, 1996;Hopkins et al.,2008), galaxy interactions, minor merger or other secular processes such as galaxy bars, disk instabilities, and clumpy cloud accretion (e.g. Silverman et al., 2011; Bournaud et al., 2012; Villforth et al., 2014). These processes may be responsible for triggering both black hole feed via accretion of gas to the center of the galaxy and star formation. However, we note that there is evidence that the most luminous AGNs are preferentially triggered by major mergers, as also found for the most powerful star-forming galaxies (e.g.Treister et al.,2012), which could indicate that to reach the high- est AGN luminosities - where the most massive BHs accreted the bulk of their mass - major mergers are required to drive sufficient quantities of gas into the central regions of galaxies. Fig.1.6shows a schematic example for theMBH− σ relation with three possible evolution-

ary tracks for merging galaxies overlaid (Medling et al.,2015).

Black holes release huge amounts of energy to their surrounding systems. Assuming a sufficiently strong coupling between BH radiative/mechanical output and the surrounding gas, the SMBHs can potentially regulate the growth of their host galaxies through AGN feed- back (e.g.Springel et al., 2005;Hopkins et al., 2010). This assumption would be consistent with the existence of a correlation between the mass of stars in the bulge and the masses of the SMBHs. In particular, theory suggest that nuclear activity regulates host galaxy growth either by high velocity AGN-driven outflows that remove the gas from the galaxy and sup- press the star formation and future black hole growth (e.g.Hopkins et al.,2006;Menci et al., 2006), or by heating it (e.g. Croton et al., 2006). The feedback process from a growing SMBH can be split broadly into two types. Using the terminology ofCroton et al. (2006), there is ‘quasar-mode’ feedback, which comprises wide-angle, sub-relativistic out-flows due to the efficient accretion of cold gas, and ‘radio-mode’ feedback, which are relativistic out- flows driven by radiation that punch their way out of the host galaxy and into the surrounding inter-galactic medium (IGM), often but not exclusively due to the relatively inefficient ac- cretion of hot gas (see Fig.1.7;Alexander & Hickox,2012). It is important to note that this radio-mode is mechanical feedback from radio jets.

Quasar-mode feedback is considered to be driven by a wind created by the luminous accretion disk. The ignition of the nucleus in a star-forming galaxy heats-up and removes the inter-stellar medium (ISM) gas from its host galaxy, thus reducing or even stopping star formation (e.g. Granato et al., 2001; Croton et al., 2006; Hopkins et al., 2010; Page et al., 2012). During this process, the flow of matter to the central SMBH can be reduced, low- ering the accretion flow and eventually extinguishing the AGN. Once the gas cools down

FIGURE 1.6:MBH− σ relation for isolated galaxies fromMcConnell & Ma(2013) (black) with