T. J. Cox Gurtina Besla (CfA), Tiziana Di Matteo (CMU), Suvendra Dutta (CfA), Loren Hoffman (CfA), Patrik Jonsson (UCSC), Dusan Keres (CfA), Elisabeth Krause (CfA/Bonn), Adam Lidz (CfA), Desika Narayanan (Arizona), Joel Primack (UCSC),Brant Robertson (KICP), Rachel Somerville (MPIA), Volker Springel (MPA), Josh Younger (CfA) Lars Hernquist, Phil Hopkins Feedback by Merger- driven AGN

projected gas distribution projected stellar distribution

Tidal torques  large, rapid gas inflows ( e.g., Barnes & Hernquist 1991 ) Triggers starburst ( e.g., Mihos & Hernquist 1996 ) Feeds BH growth ( e.g., Di Matteo et al ) BH Feedback disperses gas and reveals optical QSO Merging stellar disks grow spheroid Requires: –Major (  3:1) merger –supply of cold (i.e., rotationally supported) gas Generic Outcome of Gas-Rich Galaxy Mergers

Cox et al. (2006) Proposed Chronology of a Galaxy Merger

Note #1: Morphology at Quasar phase

Note #2: Not all AGN activity is triggered by mergers Low-mass BH (if bulge-less galaxy) or moderate-mass BH accreting by stochastic triggering, minor merger, or … High-mass BH accreting ambient gas or participating in another gas-rich major merger or …

Types of Feedback During Gas-Rich Galaxy Mergers 1. Merger/Gravitational Feedback : collisional heating of gas owing to the interaction itself 2. Star Formation Feedback : energy/mass input from high-mass stars 3. QSO Feedback : energy input from high Eddington rate BH accretion. Note that this is separate from, but a necessary precursor to, “Radio-mode” feedback.

A Typical Galaxy Merger (take 2) projected gas distribution Mass-weighted gas temperature (on a larger scale)

Hot (~T vir ) gas is produced by collision- induced shocks (and therefore depends on the merging orbit) Mainly affects low- density (outer-disk, tidal) gas (a small fraction of the original gas content) Insufficient heating to unbind gas Cox et al. (2004/6) Gravity/Merger Feedback Contours show the X-ray emission from from hot gas.

Basic energetics suggest that E fb,SN ~ E fb,BH Timescale for energy injection is NOT equivalent  SP <  SF  The power can be very different Location of energy injection is different: quasar feedback is deposited in the galactic center, star formation feedback is spread throughout the galactic disk Feedback from Star Formation and Black Holes

BH feedback during the “active phase” becomes increasingly dominant for systems of larger (total) mass Cox et al. (2007) Relative Feedback During “Active Phase”

BH feedback during the “active phase” regulates the mass of the black hole, and leads to the M BH -  relation. Di Matteo et al. (2005), Springel et al. (2005) BH Feedback During “Active Phase”

Significant coronae of hot gas is produced Emits X-rays ( consistent with E scaling relations ) Cooling time and entropy are increased ( Small systems may never cool and large systems are “primed and ready” for radio-mode feedback -see Phil’s talk from Monday ) Ejects metals AGN contributes ( significantly to the entropy ), but SN-driven winds dominate the ejection of mass and metals The Influence on Gas in the Merger Remnant

Which Feedback Influences the Structure of Merger Remnants? Stellar feedback regulates star formation & determined the structure of the merger remnant BH feedback does not! w/ BH w/o BH

Star formation quenched by black hole feedback, remnant reddens quickly Less power from starburst driven winds (factor ~ 0.1) Springel et al. (2004), Di Matteo et al. (2005) with black hole Color Evolution of Merger Remnants without black hole

Color Evolution of Merger Remnants Do we really NEED BH feedback to produce red remnants? high gas content moderate gas content

Outflows visible in absorption ( Mathur’s talk earlier, Arav/Trump in QSO, Rupke/Martin in ULIRGs, Tremonti in post- starburst galaxies, Weiner in DEEP2 ) CO spectra ( Appleton et al. 2002, Narayanan et al. 2006, Iono et al ) SZ ( Evan’s talk, Juna’s suggestion ) Signatures of BH Feedback? Narayanan et al. (2006) NGC 6240 (Iono, et al., 2007, see also Appleton, et al in NGC 985) Tremonti et al. (2006)

Conclusions: 3 Types of Feedback During Gas-Rich Galaxy Mergers 1.Merger/Gravitational Feedback : collisional heating of gas owing to the interaction itself * additional heating source 2. Star Formation Feedback : energy/mass input from high-mass stars * dominant source of feedback, regulates star formation & remnant properties * very likely determines mass and metal ejection 3. QSO Feedback : energy input from high Eddington rate BH accretion. Note that this is separate from, but a necessary precursor to, “Radio-mode” feedback. * very brief, but powerful * regulates black hole mass * contributes to heating of remaining gas * contributes to metal ejection * contributes to color evolution in massive, high gas fraction mergers Observational evidence ….. ??