observations of agn outflows and their contribution to feedback
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DESCRIPTIONObservations of AGN Outflows and Their Contribution to Feedback. Gordon Richards Drexel University. With thanks to Sarah Gallagher, Karen Leighly , Pat Hall, Paul Hewett, Nahum Arav , Daniel Proga , TJ Cox, and John Everett. Merger Scenario w / Feedback. merge gas-rich galaxies - PowerPoint PPT Presentation
Constraints on UV/Optical Continuum, BELR, and BALR Physics
Observations of AGN Outflows and Their Contribution to FeedbackGordon RichardsDrexel UniversityWith thanks to Sarah Gallagher, Karen Leighly, Pat Hall, Paul Hewett, Nahum Arav, Daniel Proga, TJ Cox, and John Everett1I was asked to talk about observations of AGN outflows and their contribution to Feedback.Ill do that in addition to plugging some work of ours from a recently submitted paper.Merger Scenario w/ Feedback merge gas-rich galaxies forms buried AGNs feedback expels the gas reveals the AGN shuts down accretion and star formation
Granato et al. 2004, DiMatteo et al. 2005, Springel et al. 2005, Hopkins et al. 2005/6a-ze.g., Silk & Rees 1998,Fabian 1999Kauffmann & Haehnelt 20002Lets start by reviewing the current feedback paradigm that has been developed over the past ~10 years.READ SLIDESo, AGNs arent unusual objects, they are just a stage in the life of every massive galaxy.Why No Big Galaxies?
Benson et al. 2003MassNumberExpectedObservedOne of the issues that feedback helps to address is the lack of really big galaxies. Based on the dark matter halo mass function, wed expect the galaxy mass function to look like the black line. But instead it looks like the grey line the most massive galaxies are missing (or rather arent as massive as wed expect). Feedback is often invoked to explain this discrepancy.3ColorMassColorRedBlueBlue CloudRed Sequence2 Types of Galaxiese.g., Faber et al. 2007
Another thing that feedback may do is to create red, dead massive elliptical galaxies.We think of galaxies being dominated by 2 types. Blue, star forming spiral galaxies and red elliptical galaxies that lack on-going star formation (i.e., they are dead).It turns out that the red galaxies tend to live in dense environments.
This led to the realization that mergers between spiral galaxies result in massive elliptical galaxies, but it isnt clear why exactly they should be dead. Perhaps feedback expelling gas is what kills them off.
4MBH-sigma From AGN Feedback
Di Matteo, Springel, & Hernquist 2005Simulations of mergers can reproduce this relationship if 5% of the AGNs radiated luminosity couples with the gas (0.5% of the rest mass enery).Lastly, but perhaps most important is the so-called M-sigma relation. Specifically, a number of authors (e.g., FM00, G00, T02) have shown a tight relationship between black holes and their host spheroids, with the BH having about 1/1000th the mass of the DM halo. This is true over a large range of masses (MW to most massive quasars).
It implies that black holes and their host spheroids "co-evolve". It is generally agreed that you need accretion to get such large black holes. So, fundamentally, AGNs must play a role in this (since an accreting SMBH = quasar). Indeed simulations that feed back 5% of the AGNs radiated luminosity to the galaxy can reproduce this relationship.Note that this is just 0.5% of accreted rest mass energy if the radiative efficiency is 0.1. 5Is Feedback Really Needed?
Wuyts et al. 2010, in prep. Still have some post-AGN star formation (still some gas).
Would get red ellipicals from merger anyway.
M-sigma may just indicate same fuel source.AGNs may not make red, dead ellipticals they just make them better.One question is whether feedback is really needed to explain these effects.Indeed, there is still some star formation (some gas) in the post-AGN phase (figure) and we might expect to get red ellipticals from mergers even without AGNs.The need for feedback to explain the M-sigma relationship may be stronger, but could just indicate the same fuel source. (Murray talk)To paraphrase the slogan of a German chemical company.READ
BASF originally stood for Badische Anilin- und Soda-Fabrik (Baden Aniline and Soda Factory).
6Feedback Mechanisms Jets Winds radiation pressure line continuum magneto-centrifugal forces thermal pressure Radiative Heating
e.g., Begelman 2004Feedback is a generic term that represents a number of different processes.Jets important in clusters and to suppression of cooling flows, but cannot be important for M-sigma in field galaxies as only a minority of AGNs are radio sources.RLF actually goes down with redshift, which suggest that jets were even less important in the past.
Winds can be driven by READ.Thermal: slow winds at large radius not a significant contribution to feedback.So, concentrate on radiation (LD) and MHD.
7Quasar vs. Radio Mode Quasar mode = cold gas accretion Radio mode = hot gas accretion (Croton et al. 2006)
N.B.: AGNs with radio jets arent necessarily radio mode objects.
I will strictly be talking about quasar mode.
One thing that is important to get clear from the start is the confusing terminology of quasar mode and radio mode feedback. Quasar mode refers to cold gas accretion, while radio mode refers to hot gas accretion.It is important to realize that AGNs with radio jets arent necessarily radio mode objects. Indeed, luminous quasars with FRII radio lobes are clearly quasar mode objects.
Urry & Padovani 1995Clouds (and Torus?) => Disk Winds
Proga 2005 (see also Everett 2005) 9So lets talk about winds.Disk-wind theory goes back a long way and has its origins in CV work. But that has now been extended to higher mass disk systems (such as quasars) and is now the generally accepted theory. The BELR "clouds" have been replaced by the wind and the "torus" may instead simply be the outer region of the wind (Elitzur). While the picture from Elvis 2000 is rather schematic, there now exist models that can accurately reproduce many aspects of central engines in quasars. (e.g., Proga, Konigl).
Accretion Disk Radiation(Gallagher et al. 2002a: Adapted from Knigl & Kartje 1994; Murray et al. 1995)
Black HoleStrong X-rays (~ light hours)Weak X-raysUV LightOptical Light (~ light years)10So, how do accretion disk winds work?Well, the accretion disk has a range of temperatures, being hotter in the center and cooler farther from the BH.
[As a result, it emits mostly weak X-rays at the inner edge, UV light in the middle and optical light at the edges.Now the accretion disk isnt solid, it has sort of an atmosphere. Made of mostly normal stuff.Carbon, Nitrogen, Oxygen, Magnesium. Just with a few less electrons.]
Accretion Disk Wind
Wind(Gallagher et al. 2002a: Adapted from Knigl & Kartje 1994; Murray et al. 1995)UV light from the accretion disk pushes on electrons in the atmosphere of the accretion disk and drives a wind. This wind deposits energy into the system.
Proga et al. 2000Dusty region11So, what happens is that the UV radiation pushes on the atoms through line transitions. The force is actually quite strong as Cross section is 10^7 times electron scattering. (Similar to the solar wind.). Ask Everett and Murray (who are here) if you want more details.
The part of the wind beyond the dust sublimation radius may constitute the torus. Indeed a torus wind could contribute significantly to feedback (as noted by Krolik & Kriss 2001)
Again, this is purely phenomenological, but simulations are becoming quite sophisticated.
Broad Absorption Line QuasarsQuasars with P-Cygni like absorption troughs reveal much about the nature of the accretion disk wind.Weak X-ray (relative to UV) allows stronger winds.
Hall et al. 02; Reichard et al. 03a,b; Tolea et al. 03; Trump et al. 06; Gibson et al. 08P Cygni profile from ejected gas
One of the acknowledged signatures of such a wind are broad absorption line troughs.These are objects that exhibit P-Cygni like absorption troughs that are thought to be due to the disk-wind outflow.Explain picture. Indeed, studies have shown that there are relationships between the intrinsic quasar properties and the broad absorption properties that are consistent with a radiation driven disk wind. For example, weak X-ray flux (relative to UV) allows stronger winds (higher v_max) to be driven.12SED/Shielding Dependencevterm ~ (GMBH/Rlaunch)1/2(cf. Chelouche & Netzer 2000; Everett 2005)
smaller Rlaunch higher vtermthicker shield more X-ray weakthinner shield less X-ray weaklarger Rlaunch lower vterm(Gallagher et al. 2006; Gallagher & Everett 2007)We can understand this previous relationship as follows:For a wind to form it has to be shielded from being over-ionized by the hot X-ray source. An inner failed wind could provide this shielding. If that shield is thicker or naturally closer in (e.g. due to a less ionizing SED), then the wind can form further in, which leads to higher velocities.
What we dont know are the detailed conditions in this wind. However, there has been considerable work on this in recent years.13UV Wind DiagnosticsCampaigns have concentrated on (Fe)LoBALs.Determine distances, outflow rates, kinetic luminosities.Find typical distance are a few kpc.Outflow rates of tens of solar masses/year.Kinetic luminosities of 0.01 L_bolCrenshaw et al. 1999Krolik & Kriss 2001de Kool et al. 2001; FIRST J104459.6+365605Crenshaw, Kraemer, & George 2003; ARAAMoe et al. 2009; SDSS J0838+2955Bautista et al. 2010; QSO 2359-1241Dunn et al. 2010; SDSS J0318-0600Talks by Gerry Kriss and Lisa Winter will certainly give more details, but Ill review some results here.The study of absorbers in quasars and Seyferts has a long history and here Ive given some references, including the Crenshaw et al. review paper from 2003. In recent years some significant strides have been made using BAL quasars. Particularly by Nahum Aravs group at VT.Note that Dunn has a historical object summary.The last 3 are part of a campaign that has READ.14SDSS 0838+2955
ergs/s = Solar masses/yr
Moe et al. 2009