Correlations Between Core Mass Deficit M def, M,  – The “Smoking Gun” for Core Scouring by Binary Black Holes John Kormendy University of Texas at Austin Kormendy, Fisher, Cornell, & Bender 2009 “Structure and Formation of Elliptical and Spheroidal Galaxies” ApJS, in press (arXiv: ) (KFCB) Kormendy 2009, in Galaxy Evolution: Emerging Insights and Future Challenges, Ed. S. Jogee et al., ASP, in press (arXiv: ) Kormendy & Bender 2009, ApJ, 691, L142 NGC 4621 NGC 720 Thanks: T. Lauer

Correlations Between Core Mass Deficit M def, M,  – The “Smoking Gun” for Core Scouring by Binary Black Holes Sérsic (1968) fn:

It is known that core mass deficits correlate with M. Merritt 2006 Milosavljević et al Assumed pre-scouring density profile ρ ∞ r -2 Assumed pre-scouring density profile ρ ∞ r – ϒ with ϒ = 2 (top), 1.75, and 1.5 (bottom). Note how much M def depends on γ. Assumed pre-scouring density profile = observed outer Sérsic profile Milosavljević & Merritt 2001 M def ≈ M  M def ≈ 10 M 

Diagnostic Departures From Sérsic Profiles. I. Cores Near the center, the profiles of many Es break below the inward extrapolation of the outer Sérsic profile into a nonisothermal core (e. g., Kormendy 1999; Trujillo et al. 2004; Ferrarese et al. 2006). Aims: 1 – More accurate measurement of M def ; 2 – To understand both core & coreless galaxies; 3 – To put BH core scouring into a global galaxy formation context.

Why estimate L def by extrapolating outer Sérsic functions to r = 0? 1 – It fits 93 – 99 % of the galaxy light to rms = mag arcsec – Sérsic extrapolation is more conservative than power law000. extrapolation.

Why estimate L def by extrapolating outer Sérsic functions to r = 0? 3 – Extra light profiles of lower-L E progenitors extend the large-n outer Sérsic profiles of giant Es inward.

Origin of Cores = Black Hole Scouring? Galaxy mergers preserve the highest central density in the progenitors. But higher-luminosity galaxies have fainter µ oV. Problem = how to prevent mergers from destroying the core FP relations (Kormendy 1993; Faber et al. 1997). Possible solution: supermassive black hole binaries scour cores: - Merge two galaxies that contain black holes  black hole binary - The binary orbit decays as the black holes fling stars to larger radii - Result: depleted mass  mass of the binary for every dissipationless merger (Begelman, Blandford, & Rees 1980; Ebisuzaki et al. 1991, Makino & Ebisuzaki 1996; Faber et al. 1997, Milosavljević & Merritt 2001; Milosavljević et al. 2002, Merritt 2006)

Diagnostic Departures From Sérsic Profiles. II. “Extra Light” Near the Center Kormendy (1999, Rutgers Symposium): Some low-luminosity ellipticals have excess central light above the inward extrapolation of a Sérsic fit to the outer profile.

Interpretation: The excess light closely resembles the extra central components made in dissipative merger simulations: Mihos & Hernquist (1994) : TREESPH code with 1. stars, gas, DM; 2. ∑ SFR  ∑ GAS 1.5 ; 3. bulge/total = 0.

Conclusion Cores are indicative of “dry mergers” – ones with little dissipation and with binary black scouring after the last major merger. Excess central light is a signature of “wet mergers” – of dissipative starbursts during the last major mergers. Hopkins

Normal and low luminosity Es – rotate rapidly, – are nearly isotropic oblate spheroids, – are substantially flattened (E3), – are coreless – have disky-distorted isophotes. Giant ellipticals – are essentially non-rotating, – are anisotropic and triaxial, – are less flattened (E1.5), – have cuspy cores, – have boxy-distorted isophotes. Kormendy & Bender (1996) The E-E Dichotomy: There are two kinds of elliptical galaxies (e. g., Bender 1988; Bender et al. 1989; Kormendy et al. 1994; Lauer et al. 1995; Kormendy & Bender 1996; Gebhardt et al. 1996; Tremblay & Merritt 1996; Faber et al. 1997; Rest et al. 2001; Lauer et al. 2006; SAURON papers)

Virgo Cluster Distance = 17 Mpc 1 arcsec = 82 pc 28 elliptical galaxies = 1/3 of Virgo luminosity  2/3 of Virgo stellar mass

KFCB derive composite surface brightness profiles for “all” ellipticals, 5 bulges, and 10 Sphs in the Virgo Cluster from published photometry + our photometry. Emphasis: high accuracy, high dynamic range

Core “fundamental plane” correlations define what it means to be an elliptical galaxy. Kormendy (1985, 1987) E ≠ Sph ≈ S,Im globular clusters

Fundamental Plane Correlations Show That Sph Galaxies Are Not Faint Es Kormendy (1988)  e – r e correlation ≈ edge-on FP has small scatter (Saglia et al. 1992; Jørgensen et al. 1996). Kormendy (2009); KFCB (2009)

Fundamental Plane Correlations Show That Sph Galaxies Are Not Faint Es Kormendy (1988)  e – r e correlation ≈ edge-on FP has small scatter (Saglia et al. 1992; Jørgensen et al. 1996). Kormendy (2009); KFCB (2009) Es were formed by major mergers. Sphs are defunct S+Im galaxies transformed by internal processes like supernova-driven baryon ejection and by environmental processes like galaxy harassment and ram-pressure gas stripping.

BHs do not correlate with Sph or Im galaxies or with galaxy disks (Kormendy & Gebhardt 2001, 20 th Texas Symposium, 363).  Further discussion: Es and bulges only.

All 10 M V ≤ Es in Virgo have cores.

All 18 M V ≤ Es in Virgo have extra light. Often extra light is disky  it formed dissipatively. Usually extra light stars are essentially as old as rest of galaxy.

E profiles are bimodal (e. g., Gebhardt et al. 1996; Lauer et al. 2006): either they have cores, or they have “extra light” (Kormendy et al. 2009). Lauer et al Kormendy et al. 2009

Normal and low luminosity Es – rotate rapidly, – are nearly isotropic oblate spheroids, – are substantially flattened (E3), – are coreless & have extra light near the center above the inward extrapolation of the outer Sérsic profile, – have disky-distorted isophotes, – have n ≤ 4, – contain younger, ~ Solar-composition stars. The E-E Dichotomy: There are two kinds of elliptical galaxies Giant ellipticals – are essentially non-rotating, – are anisotropic and triaxial, – are less flattened (E1.5), – have cuspy cores, – have boxy-distorted isophotes, – have n > 4, – contain old,  -enhanced stars. Kormendy & Bender (1996)

The E-E Dichotomy: There are two kinds of elliptical galaxies Normal and low luminosity Es – rotate rapidly, – are nearly isotropic oblate spheroids, – are substantially flattened (E3), – are coreless & have extra light near the center above the inward extrapolation of the outer Sérsic profile, – have disky-distorted isophotes, – have n ≤ 4, – contain younger, ~ Solar-composition stars. –the last mergers were dissipative. lk BH binary scouring was overwhelmed by dissipative starburst. [  /Fe] is consistent with prolonged merger history. Giant ellipticals – are essentially non-rotating, – are anisotropic and triaxial, – are less flattened (E1.5), – have cuspy cores, – have boxy-distorted isophotes, – have n > 4, – contain old,  -enhanced stars. – last mergers were dissipationless, followed by BH binary scouring. [  /Fe]  star formation finished in first billion years; subsequent dissipationless mergers are OK. Galaxy formation: we interpret the above as evidence that:

Formation of the Two Kinds of Elliptical Galaxies Normal and low luminosity Es seem entirely consistent with standard galaxy formation in a hierarchically clustering universe. –the last mergers were dissipative. lkBH binary scouring was overwhelmed by dissipative starburst. [  /Fe] is consistent with prolonged merger history. Giant ellipticals and maybe also the biggest BHs seem to have formed in a suspiciously anti-hierarchical manner. Are we missing something from our galaxy formation picture? last mergers were dissipationless, followed by BH binary scouring. [  /Fe]  star formation finished in first billion years; subsequent dissipationless mergers are OK. Galaxy formation: we interpret the above as evidence that:

Formation of the Two Kinds of Elliptical Galaxies AGN energy feedback quenched star formation after < 1 Gyr. Problem: AGNs are episodic. How can we guarantee that an AGN was switched on every time a gas-rich galaxy got accreted? Giant ellipticals and maybe also the biggest BHs seem to have formed in a suspiciously anti-hierarchical manner. Are we missing something from our galaxy formation picture? Popular explanation of anti-hierarchical star formation in giant Es:

Potsdam 2006 Thinkshop = Watershed for AGN Feedback Best: AGN feedback needs a “working surface” = x-ray-emitting gas in giant Es and clusters Fabian, Forman: Chandra  In Perseus and in M87, directed energy from jets is being redistributed more isotropically via bubbles blown, compression waves, …. OK, this doesn’t yet prove that the energy can be thermalized. But: Chandra 900 ks image of Perseus cluster, unsharp-masked at right (Fabian et al. 2006)

Essential new idea: hot gas = energy storage medium. Which Es are likely to have significant AGN feedback? Bender et al. (1989): Disky Es have neither AGNs nor hot gas  AGN feedback is weak, consistent with our conclusions re: formation of extra light via starbursts in dissipative mergers. Boxy Es have AGNs and hot gas = working surface  AGN feedback is plausible and can protect them from star formation caused by late accretion of gas-rich galaxies. KFCB: AGN feedback may solve the problem of episodic energy input: We suggest that AGN feedback into x-ray gas only in giant-boxy-core galaxies and their progenitors is the reason why the E - E dichotomy arose.  Boxy Disky  X-Ray L Radio L

L X – L B correlation  X-ray gas participates in the E – E dichotomy. KFCB update of Fig. 9 in.Ellis & O’Sullivan 2006

Three possible heating mechanisms: AGN energy feedback, cosmological gas infall (Dekel & Birnboim 2006), recycling of gas from old stars. Any combination of these is OK for our formation picture. The X-ray gas makes dry mergers dry and allows BH core scouring to happen.

Implications of Extra Light in Low Luminosity Es We believe that cores are produced by binary black hole scouring. Low-luminosity Es like M32 and NGC 3377 contain black holes. They are believed to have formed via major mergers. But they contain extra, not missing, light near the center. M def ≈ 10 M  ; almost no scatter. Suggests: BHs and cores are connected. M excess ~ uncorrelated with M .

Implications of Extra Light in Low Luminosity Es We believe that cores are produced by binary black hole scouring. Low-luminosity Es like M32 and NGC 3377 contain black holes. They are believed to have formed via major mergers. But they contain extra, not missing, light near the center. Why did binary black hole scouring fail? Suggestion: The dissipative starburst that produced the extra light also swamped black hole scouring. The mass excess is determined by the progenitors’ gas fractions, dissipation, and star formation. Therefore M excsss does not correlate much with M .

Our results are consistent with popular suggestions that the galaxy mass function is whittled by AGN feedback at the high-mass end and by SN at the low-mass end. Cattaneo et al. 2009, Nature, in press Little feedback

M def ≈ 10 M  appears consistent with a few dry mergers: M def / M  can be ~ 4 per merger (Merritt et al. 2007) and ~ 5 more if remnant BHs recoil from anisotropic gravitational radiation emitted when binary BHs merge (Merritt et al. 2004; Boylan-Kolchin et al. 2004; Gualandris & Merritt 2008).

Kormendy & Bender (2009) There is a large dispersion around canonical BH mass fraction ≈ 0.13 % (Merritt & Ferrarese 2001; Kormendy & Gebhardt 2001). But: L def /L correlates tightly with M  /M over the whole range.

Kormendy & Bender (2009) L def – M  correlation is surprisingly tight.

Note: This is a correlation between two observables. It involves no modeling. Kormendy & Bender (2009)

M –  and M – L def give us two independent estimates of M. In particular, they give us a “third opinion” when M –  and M – L bulge disagree (Lauer et al. 2007).

Kormendy, Fisher, Cornell, & Bender 2009, ApJS, in press (arXiv: ) Kormendy & Bender 2009, ApJ, 691, L Core mass deficit correlates with BH mass and host galaxy  with scatter ≈ measurement errors. These tight correlations are a “smoking gun” that connects cores with BHs. They support the hypothesis that cores are scoured by binary BHs. Conclusion

Kormendy, Fisher, Cornell, & Bender 2009, ApJS, in press (arXiv: ) Kormendy & Bender 2009, ApJ, 691, L Core mass deficit correlates with BH mass and host galaxy  with scatter ≈ measurement errors. Given heterogeneous merger histories, it is astonishing how much regularity there is to core formation in elliptical galaxies. Conclusion