Adi

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Is the term “negative feedback” accurately defined and what evidence we have that outflows and winds are doing more than just driving some material out of the system?

Can we distinguish a “real” negative feedback, one that stops the stellar growth of a galaxy, from a “negative” negative feedback, with clear signs of outflow yet little effect on galaxy evolution?

Are the properties of such feedback events different an low and high redshift, low and high AGN luminosity, and at different stages of evolution, e.g. immediately following the ULIRG phase or in galaxies showing no signs of interaction?

I will show several specific examples of outflows that span a range of properties directly related to the above questions.

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I will present some observational results illustrating the properties of AGN-driven outflows and their effect on star formation in their host galaxies. In particular I will present multi-band observations

tracing both the molecular and ionized phase of the ISM, both in local and distant galaxies, illustrating that AGNs can drive extremely powerful and energetic outflows, which can expel a large fraction

of the gas in their host galaxies, hence suppressing star formation (negative feedback). However, I will also show evidence that in some cases AGN-driven outflows can actually trigger star formation, both in their host galaxy discs and even in the outflow itself. This is a new mode of star formation, which can contribute significantly to galaxy evolution. I will conclude by presenting the exciting prospects of further investigating these effects in the near future.

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1. Can AGN-powered molecular jets appear as disk-winds similar to what we see in protostars? If so – will we then see molecular jets also in the quasar mode of accretion?
2. Is it possible that molecular jets are important processes in solving the angular momentum problem for SMBH growth – or is the jet of NGC1377 a unique phenomenon?
3. What is the fate of the gas in AGN/starburst outflows? Can it fall back onto the galaxy again – serving as an “engine” for SMBH and stellar growth? If so – how is this then linked to the “cold accretion” hypothesis?
4. How is it possible that molecules are surviving in 1000 km/s outflows? Are the molecules carried out from the disk, or are they formed in-situ from the hot gas?
5. What are the physical conditions of the gas in the outflow? Can the gas clumps really be self-gravitating – or are we seeing diffuse, unbound molecular gas. (A related question is if the gas can form stars in the flow). The answer to this queston is important also for the mass estimates of the cold gas, which currently has at least a factor of 10 uncertainty.
6. Are the physical conditions and ultimate fate of the gas different in AGN and starburst flows?
7. Will AGN and starburst feedback impact their host galaxies differently? Are quasars and their outflows really “a waste of space”? (quote from J. Binney)

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I will present the latest results from our on-going multi-wavelength survey of galactic-scale ouflows in nearby actively star-forming and/or black-hole-accreting galaxies with an emphasis on the cool neutral and molecular gas phases. I will review the structure, mass, energetics, power source, extent, and dependence on host galaxy properties of these gas phases in galactic outflows. Very high resolution 3D observations of the nearest and best known starburst- and AGN-driven outflows will be discussed to provide further insight into the physical entrainment and mass-loading mechanisms of these outflows. Overall, our results suggest that the cool neutral and molecular gas phases are the key to understanding galactic outflows in gas-rich galaxies: they carry significant amounts of mass and energy, show evidence for driving by the central black hole, and extend further from the galaxy than previously known.

A few obvious questions that come to mind:

• observational: uncertainties on outflow mass & energetics
• observational: uncertainties/limitations on outflow size measurements
• observational & theoretical: observational evidence for entrainment of cool ISM vs in-situ formation of cool clumps in the hot wind

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Feedback: The basic questions are where, when, how, how much and how do we observationally determine it.

1. When does AGN feedback occur: at high z, low z, at all redshifts. Is the amount of feedback a function of cosmic time/galaxy mass/star formation rate.
2. In which galaxies is feedback occurring and what are the parameters of the host galaxy that are correlated with feedback. Can we actually measure the direct effect of feedback on star formation.
3. Where in the galaxy are the signatures of  feedback found- in the nucleus, in the outer regions, in the halo.
4. Are the signatures of feedback different in spirals, ellipticals, rapidly star forming galaxies?
5. What is the physical mechanism(s) via which the AGN inhibits, stimulates or modifies star  formation?
6. Are the observed AGN winds related to feedback and if so, how
7. What future observations are necessary to answer these questions?

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Why over-ionization is a problem in AGN outflows? Is the problem unique to AGN or do other astrophysical outflows have a similar problem?

What are the consequences of the over-ionizaton in magnetically driven outflows and in radiative driven outflows?

Can screening help to solve the over-ionization problem?

Do we know the geometry and SED of the AGN radiation well enough to assess the severity of the problem?

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The similar values of the radiation pressure incident on the BLR, and the pressure  of the gas at BLR, suggest the gas is being compressed by the incident radiation pressure. This radiation pressure compression (RPC) may also provides a natural solution to the overionization problem for the BAL outflow.

How can one test this solution?

Furthermore, what is the source of gas which forms the BLR?

What are the expected properties of a wind formed by the ablation of the RPC BLR gas?

Can RPC ablation explain the low fraction of LBALQs?  

Can RPC ablation explain a smooth outflow in velocity space, yet highly clumped in real space?

More generally, how can one tell that an outflow is driven by radiation pressure?

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Absorption measure distribution in AGN can be determined since we are able to see absorption lines on highly ionised elements with CHANDRA/XMM-Newton precision. AMD is best tool to measure the global distribution of this warm gas which interacts with radiation coming from the nucleus. The observed deeps in AMD are well explained by the eventual thermal instability in caused by strong gas irradiation with hard X-rays. I will present how the distribution of absorbed gas depends on gas physical parameters and what has the biggest influence on the location of observed deeps and AMD normalisation. I will discuss the best warm absorber model which explains the observed AMD shape in currently available sources. Some questions that arise are:

1. What is the main difference in the cloud sructure between Radiation Pressure Confinement and Constant Total Pressure?
2. What main physical parameter or physical process are responsible for the AMD normalization?
3. Can thermal instability caused by illumination create the wind in AGN?
4. Do AGN winds remain static or stationary in the gravity field of central BH? 

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While there has been an increasing number of high-quality CCD/dispersive spectroscopic data for various types of outflows both in AGNs and XRBs, their physical conditions, including its launching mechanisms and global perspective, are yet to be understood well to date. Many attempts have been made in the past decades from both observations and theoretical calculations to better constrain the underlying physical quantities (e.g. columns, velocities and ionization state) that yield the observed spectra. As a promising acceleration mechanism, I will discuss some of the speculative as well as fundamental nature of magnetically-driven accretion-disk winds in genera addressing its weaknesses and strengths as a candidate model. Motivated by the recent state-of-the-art X-ray observations, for example, with Chandra/HETGS, I will further introduce some of the very interesting properties of the warm absorbers (WAs) and ultra-fast outflows (UFOs) in the context of the MHD-driven wind view. Most importantly, an ultimate question will be “How one can distinguish MHD-driven winds from the others?” and I would like to stimulate our  discussion in this respect as well. 

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We propose a new dynamical model for obscuring tori of active galactic nuclei motivated by our recent radiative magnetohydrodynamics simulation. The model consists of a momentum-driven outflow from the inner edge powered by ultraviolet and infrared radiation, as well as a mid-plane inflow feeding it. The outflow in our model occupies a large solid angle and has high enough latitude to provide substantial covering in the optical and the ultraviolet. We consider how central irradiation may affect the inflow, and what heavy mass loss to the outflow may imply for the inflow.

Questions for discussion:

1. Any reasonable torus wind model (e.g. thermally driven, radiation-driven, magnetocentrifugal wind) predicts ~0.1 M⊙/year for 1e7 solar mass AGN. Unless the torus is very Compton thick and hence contains a lot of mass, it can only last ~10s of orbits. How can mass be supplied quickly enough for the torus to be in a steady state? Or is the torus always a transient phenomenon?
2. How can observations constrain the geometrical thickness and rotational profile of the inflow portion of the torus?
3. Besides with interferometry, how can the radiation-driven outflow be observed and its properties compared with simulations (e.g. with line ratios)?
4. Is there any connection between the inner surface of the torus and the BLR? Is line-driving significant near the inner edge?