Literature Rivews for AGN FB in Rotating ETGs

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## Misalignment between black hole and its host

• King & Pringle 07
• First, Kinney et al. (2000; see also Nagar&Wilson 1999) found that in a sample of nearby (z > 0.031) Seyfert galaxies, the direction of the jet from the central black hole, and therefore presumably the orientation of the central regions of the accretion disc, were unrelated to the orientation of the disc of the host galaxy. Secondly, Schmitt et al. (2003) surveyed extended [O III] emission in a sample of nearby Seyfert galaxies, and found that although the [O III] emission is well aligned with the radio, there is no correlation between its orientation and the major axis of the host galaxy. Assuming that the orientation of the [O III] emission is governed by the geometry of the inner torus, of typical radius 0.1–1.0 pc (e.g. Antonucci 1993), this means that the central disc flow has angular momentum unrelated to that of most of the gas in the host galaxy.

## Angular momentum transport

• Cruz-Osorio, Sanchez-Salcedo, Lora-Clavijo 17
• Some attempts have been made to give an accretion rate prescription taking into account the gas angular momentum (e.g. Power et al. 2011). Hopkins & Quataert (2011) developed a sub-grid model, which can be incorporated in cosmological simulations, based on analytical calculations about angular momentum transport and gas inflow. A novel refinement scheme has been presented in Curtis & Sijacki (2015) which improves the estimation of the gas properties close to the accretion radius (see also Curtis & Sijacki 2016). Rosas-Guevara et al. (2015) explore the effect of accounting for the angular momentum by using an improved accretion model that includes the circularization and subsequent viscous transport of infalling material. On the other hand, a sub-grid model that distinguishes between hot and cold gas accretion has been implemented by Steinborn et al. (2015).
• Angles-Alcazar, Faucher-Giguere, Quataert+17
• most of the gas in the central ∼100 pc is cold and rotationally supported when BHs grow efficiently, which justifies the use of the gravitational torque model.
• Power, Nayakshin, King 11
• angular momentum provides an efficient natural barrier to accretion and so only the lowest angular momentum material will be available to feed the black holes.

## $\alpha$-viscosity

• Rosas-Guevara+15
• values of $\alpha$-visc lie in the range ∼0.1–0.3 from observational evidence (Buat-Menard, Hameury & Lasota 2001; Cannizzo 2001a,b; Schreiber et al. 2004; King, Pringle & Livio 2007)
• the structure of the circularization disc we are considering is completely unclear, as is the dominant viscous mechanism on relevant scales. These issues are discussed extensively in the literature (e.g. Shlosman, Begelman & Frank 1990, Hopkins & Quataert 2010; King, Zubovas & Power 2011; Power et al. 2011) because the long time-scales implied by the Shakura–Sunyaev formulation make it hard to understand the high efficiency of accretion required to create supermassive BHs at very high redshift. On the scales relevant to our simulations, the appropriate transport mechanism is likely to be gravitational instability (Hopkins&Quataert 2010, 2011) rather than the magnetorotational instability
• King+07
• Shakura & Sunyaev (1973) argued that magnetic fields are the likely way in which a shearing disc flow transports angular momentum from rapidly rotating fluid to more slowly rotating fluid further out. This concept was given impetus with the realization (Balbus & Hawley 1991) that what is now called the magnetorotational instability (MRI) can provide the necessary feedback to maintain a magnetic dynamo in accretion discs.

## Galactic Rotation

• Posacki, Pellegrini, Ciotti 13:
• kinetic energy associated with the stellar ordered motions may be thermalized less efficiently.
• Johnson, Harrison, Swinbank+17
• A surprising discovery has been that while high-redshift samples are kinematically diverse, with a higher incidence of mergers than observed locally (e.g. Molina et al. 2017), many galaxies appear to be rotationally supported (e.g. Forster Schreiber et al. 2009; Epinat et al. 2012; Wisnioski et al. 2015; Stott et al. 2016; Harrison et al. 2017). … the dynamical maps of these galaxies reveal a smooth, continuous velocity gradient
• Kinematic surveys have revealed that while typical rotation velocities of high-redshift disks are similar to those seen locally, intrinsic velocity dispersions are much higher (e.g. Genzel et al. 2008; Lehnert et al. 2009; Gnerucci et al. 2011; Epinat et al. 2012; Newman et al. 2013; Wisnioski et al. 2015; Turner et al. 2017). These dispersions are supersonic and most likely represent turbulence within the interstellar interstellar medium (ISM).

## Problem of Bondi Accretion

• Cruz-Osorio, Sanchez-Salcedo, Lora-Clavijo 17
• Using simulations with a resolution of 0.1 pc, Negri & Volonteri (2017) find that AGN feedback can keep the BH in a self-regulation regime, and show that Bondi subgrid algorithms in low resolution simulations can both under- and over-predict the actual accretion rates.
• Rosas-Guevara+15
• A major concern is that the Bondi accretion rate is inappropriate when the accreting material has significant angular momentum.

## Inner bar structure

• Du+17:
• one-third of barred galaxies also host a short inner bar of general radius < 1 kpc (Erwin & Sparke 2002; Laine et al. 2002; Erwin 2004, 2011); such systems are termed double-barred (S2B) galaxies. At sub-kpc scales short inner bars have been hypothesized to be an important mechanism for driving gas inflows into the center, efficiently feeding BHs (e.g. Shlosman et al. 1989; Hopkins & Quataert 2010). Thus, in order to understand the secular growth of BHs, a crucial question is under what conditions short inner bars can survive the presence of a BH

## Light Curve (Downsizing)

• Fiore, Feruglio, Shankar+17
• Franceschini et al. (1999) were among the first to realise that the luminos- ity dependent evolution of AGN, with lower luminosity AGN peaking at a redshift lower than luminous QSOs (Ueda et al. 2003, 2014; Fiore et al. 2003; La Franca et al. 2005; Brandt & Hasinger 2005; Bongiorno et al. 2007; Aird et al. 2015; Brandt & Alexander 2015), mirrors that of star-forming galaxies and of massive spheroids. These trends, dubbed “downsizing” by Cowie et al. (1996), and in general the relationship between the evolution of AGN and galaxy growth, may arise from feedback mechanisms linking nuclear and galactic processes.

## X-ray

• Posacki, Pellegrini, Ciotti 13:
• at any fixed $L_{B}$, rounder systems had larger total $L_{X}$ and $L_{X}/L_{B}$, a measure of the galactic hot gas content, than flatter ETGs and S0 galaxies
• rotational properties for the ETGs of the SAURON sample, confirming that slowly rotating galaxies can exhibit much larger luminosities than fast-rotating ones.
• Since, for a fixed galaxy mass, a decrease of $T_{\star}$ due to rotation is predicted to be potentially stronger than produced by shape without rotation, we propose that mass, a decrease of $T_{\star}$ due to rotation is predicted to be potentially stronger than produced by shape without rotation, we propose that not thermalized stellar streaming is a more efficient cause of the (possibly) lower $T_{X}$.
• Negri+14:
• Explanations based on energetic effects suppose that the ISM in flat and rotating galaxies is less bound than in more round and non-rotating galaxies of similar luminosity (and so of similar SNIa energy input) so that in the former objects the ISM is more prone to develop a global/partial galactic wind, with the consequent de- crease of $L_{X}$.
• underluminosity of rotating galaxies with medium to large σe8 is due to a different flow evolution driven by the presence of angular momentum, which prevents the gas from accumulating in the central regions, leading to the creation of a very hot, low-density atmosphere in the centre, and eventually resulting in a lower total $L_{X}$
• the presence of recurrent cooling episodes driven by rotation, which further contribute to the lowering of $L_{X}$.
• Negre, Ciotti, Pellegrini 14:
• it tends to unbind the gas; therefore, when rotation is unthermalized, the ISM is less heated but it is also less bound.
• large-scale instabilities may be at the origin of the well-known observational ‘X-ray underluminosity’ of flat and rotating ETGs mentioned above (Eskridge et al. 1995; Sarzi et al. 2013).
• the X-ray underluminosity and coolness of IS and CR models is not just due to a reduction of the injection energy in them, but – more importantly – due to the global evolution of the ISM induced by ordered rotation.

## Star Formation

• Negri+14:
• among ETGs, it is only in fast rotators that some degree of star formation is observed
• Zubovas, King 16:
• star formation rate and dynamical pressure in the galactic disc and compare this with the outflow pressure.We find that AGN outflows can produce a significant enhancement of star formation, especially in the outskirts of galaxy discs. This process helps eventually quench star formation from inside out.

### Pellegrini, S., Ciotti, L. & Ostriker, J.P., 2012. X-RAY PROPERTIES EXPECTED FROM ACTIVE GALACTIC NUCLEUS FEEDBACK IN ELLIPTICAL GALAXIES. ApJ, 744, 21 [Accessed November 25, 2015]

• medium- to high-mass galaxies, heating is required by the following empirical arguments (—> importance of AGN Feedback as a heating source):
• the large amount of gas lost by the passively evolving stellar population during the galaxies’ lifetime is not observed
• bright active galactic nuclei (AGNs), as would be expected given the predicted mass accretion rate, are not commonly seen in the spheroids of the local universe
The solution requires either steady heating or heating with bursts on a timescale $\Delta t \approx t_{\rm cool}$.
• how much radiative and mechanical energy and momentum output from the SMBH can effectively interact with the surrounding ISM, and what the resultant SMBH masses are, is difficult to establish.
• Accretion-fueled feedback thus proves effective in suppressing long lasting cooling flows and in maintaining SMBH masses within the range observed today, since the gas is mostly lost in outflows or consumed in starbursts.
• Positive / Negative Feedback
• Positive: the final mass of newly formed stars in the kiloparsec-scale cold shells originated by the AGN feedback during the outbursts is significantly larger than in pure cooling flow models. From this point of view, the AGN activity induces star formation.
• Negative: AGN activity also terminates star formation because, at the end of each major accretion episode, feedback is strong enough to empty the galaxy of gas on the kiloparsec scale.
• the aperture solid angle of the conical nuclear wind increases with increasing $l \equiv L_{\rm BH}/L_{\rm Edd}$.
• while radiative effects mainly work on the kiloparsec scale, mechanical feedback from the AGN winds is more concentrated and affects the ISM on the $\sim 100$ pc scale.
• outburst precursor is the off-center growth of a thin shell of dense gas (at a radius of $\sim 0.5–1$ kpc) that progressively cools below X-ray-emitting temperatures and falls toward the center.
• Strong intermittencies at an earlier epoch, with $L_{\rm BH}$ reaching the Eddington value, become rarer and rarer with time, as the mass return rate from the stellar population declines, until a smooth, hot, and very sub-Eddington accretion phase establishes.
• massive SMBHs are mostly radiatively quiescent, and the fraction of them at luminosities approaching their Eddington limit is negligible (e.g., Ho 2008).
• the fraction of active systems can be interpreted as a duty cycle for SMBHs in a given mass range. Greene & Ho reported duty-cycle values of the order of $4\times10^{−3}$ for SMBHs of masses of $10^{7} M_{\odot}$, declining at increasing mass. Similar duty-cycle values of $\sim 2\times10^{−3}$, decreasing at increasing SMBH mass, were reported by Heckmanet al. (2004).
• sudden increase of the gas emission during outbursts is due to the increase in temperature and density in the central galactic regions ($\simeq 10^{2} - 10^{3}$ pc) caused by radiative gas heating (Compton and photoionization) and by compression due to direct and reflected shock waves produced by mechanical and radiative feedback which are associated with the AGN and the starburst.
• Negative: Negative radial gradients, as shown by the model temperature during quiescence, are common among ellipticals, as revealed most recently by Chandra observations
• Positive (hot gas-rich environment or jet):
• positive outer gradient is shown by galaxies in high-density environments, suggesting the influence of circumgalactic hot gas.
• weak radio AGNs distribute their heat locally and host negative inner temperature gradients, whereas more luminous radio AGNs heat the gas more globally through a jet or rising bubbles and produce a flat profile or a positive gradient
• fragmentation of the cold shell which causes a lower gas compression while falling to the center.
• X-ray surface brightness becomes flatter in shape with increasing time, since the emission level decreases mostly in the central galactic regions (within $R_{e}$). This important effect is produced by the nuclear outbursts which remove gas from the center.
• bright ellipticals imaged with Chandra (e.g., Loewenstein et al. 2001) show a brightness profile that is quite flat within the central ~1 kpc, a feature impossible to reproduce with pure inflow models, while it resembles the profile of the “pre-burst” phase
• Disturbances such as shells and ripples farther out in the galaxy last < 0.2 Gyr and are more likely to be observed.
• a few galaxies without currently evident extended radio emission, but with signs of an outflow and hot central gas, such as NGC4552 (Machacek et al. 2006)
• These feedback events must leave signatures on the X-ray properties of the galaxies; indeed, the observed temperature and brightness profiles often cannot be fit with smooth profiles, such as those predicted for galactic winds or cooling flows (e.g., Sarazin 2012; Statler 2012)
• additional mechanism may be at work to further reduce the mass available for accretion; this could be provided by the mechanical feedback of a (nuclear) jet, and/or by a wind from an RIAF. Angular Momentum
• duty cycle likely increases with galaxy mass because an outburst has a greater impact in less massive (and less gas-rich) systems, which are then “on” for a shorter time (Ciotti & Ostriker 2012).

### Ciotti, L. et al., 2015. AGN feedback and star formation in ETGs: negative and positive feedback. arXiv [Accessed November 3, 2015].

• the stellar mass losses produced during stellar evolution cyclically feed a central gas inflow, and then trigger the QSO activity in isolated ETGs (sometimes considered “red and dead”).

### Zubovas, K. & King, A., 2016. The small observed scale of AGN-driven outflows, and inside-out disc quenching. arXiv [Accessed July 26, 2016].

• the effects of AGN feedback upon the host galaxies: One question is the range of spatial scales over which outflows are found. Another question is the possibility of the outflow triggering star formation in the galaxy disc.
• Modern galaxy evolution models typically include feedback from active galactic nuclei (AGN) in order to explain the drop-off in the galaxy mass function compared with the expected halo mass function above $M_{*} \simeq 10^{11}\, M_{\odot}$, prevent the cooling catastrophe in galaxy clusters and produce the scaling relations between galaxies and their central supermassive black holes (SMBH).
• star formation rate and dynamical pressure in the galactic disc and compare this with the outflow pressure.We find that AGN outflows can produce a significant enhancement of star formation, especially in the outskirts of galaxy discs. This process helps eventually quench star formation from inside out.

### Pontzen, A. et al., 2016. How to quench a galaxy. ArXiv [Accessed July 12, 2016].

• The low level of black hole accretion can be sustained even when there is insufficient dense cold gas for star formation. Conversely, supernova feedback is too distributed to generate outflows in high-mass systems, and cannot maintain quenching over periods longer than the halo gas cooling time.