The Building Up of the Black Hole - Stellar Mass Relation

1. The Building Up of the Black Hole - Stellar Mass Relation Alessandra Lamastra collaborators: Nicola Menci1, Roberto Maiolino1, Fabrizio Fiore1, Andrea Merloni2 1 INAF - Osservatorio Astronomico di Roma 2Max-Planck-Institut fur Extraterrestriche Physik

2. SMBH & galaxies co-evolution • Supermassive Black Holes (SMBH, MBH=106-109 M) are a ubiquitous constituent of spheroids in nearby galaxies (Kormendy & Richstone 1995) Tight link between the growth of SMBH (AGN phase) and the formation of the host galaxy • In the local Universe the black hole mass strongly correlates with the properties of the spheroidal component of the host galaxy (Magorrian et al. 1998, Ho 1999, Gebhardt et al. 2000, Ferrarese & Merritt 2000, Graham et al. 2001) Which is the physical nature of the SMBH-galaxy connection? MBH-M* MBH-σ* MBH-Lbulge Which are the relative time scales for star formation and for SMBH growth? How and when the AGN emission affects the galaxy properties? Haring & Rix 2004 Tremaine et al. 2002 Marconi & Hunt 2003

3. The Evolution of the MBH-M*relation stellar mass assembly BH growth Haring & Rix 2004

4. (1+z) The MBH-M* relation at high redshift Peng et al. 2006 McLure et al. 2006 Maiolino et al. 2009 Merloni et al. 2010 Decarli et al. 2010 Alexander et al. 2008

5. Detailed predictions based on semi-analytic model (Menci et al. 04,05,06,08) + + gas cooling, star formation SN feedback,… DM merging trees SMBH growth, AGN, AGN feedback • DM merging trees: Monte Carlo realizations • Dynamical processes involving galaxies within DM haloes • Cooling, Disc properies, Star formation and SNae feedback • Starbursts triggered by merging and fly-by events • Growth of SMBH from BH merging + accretion of galactic gas destabilized by galaxy encounters (merging and fly-by events) • Feedback from the AGN associated to the active, accretion phase Rate of encounters Fraction of galactic gas accreted by the BH Stellar content of the host galaxies duty cycle Physical, non parametric Model.Computed from galactic and orbital quantities

6. Initial (z≈4-6) merging events involve small clumps with comparable size High merging rate Last major merging at z≈3 for M≈3X1012 M The evolution of Dark Matter Haloes Springel et al. 2005 • Galaxy formation and evolution are driven by the collapse and growth of dark matter (DM) haloes, which originate by gravitational instability of overdense regions in the primordial DM density field • The primordial DM density field is taken to be a random, Gaussian density field with Cold Dark Matter (CDM) power spectrum within the “concordance cosmology” (Spergel et al. 2007). Properties of DM merging trees Phase 1 At later times, merging rate declines Accretion of much smaller clumps Phase 2

7. Star formation Blue galaxies Frequent galaxy interactions Rapid cooling (high gas density) Starbursts with large fraction of gas converted into stars Drop of interaction rate Decline of cooling rate Quiescent and declining star formation z>2 Red galaxies z<2 Menci et al. 2005, 2006 Two channels of star formation may convert the cold gas into stars: • Quiescient star formation Cf. with Kennicutt law • Starburst driven by (major+minor) merging and fly-by events (time scale 10-50 Myr, SFR up to 1000 M/yr) Supernovae feedback:

8. Accretion onto SMBH and AGN emission (Menci et al. 2006,2008) • The BH accretion is triggered by galaxy interactions (merging and fly-by events) Black hole accretion rate Fraction of accreted gas • Larger fraction of accreted gas for • massive haloes • high z (m’/m≈1) Interaction rate Higher interaction rate at high z AGN feedback: associated to the active, accretion phase Hydrodynamic N-body simulations (e.g. Di Matteo et al. 2005, Hopkins et al. 2006, Springel et al. 2005) • Galaxy mergers as triggers for BH accretion • Role of the AGN feedback

9. Testing the model Local stellar mass function Tully-Fisher relation data points: 2dF survey (Cole et al. 2001) shaded region: Mathewson et al 1992 Willik et al. 1996 Giovanelli et al. 1997 2MASS survey (Bell et al. 2003) B-band luminosity function data points: z=0.1 La Franca et al. 2005 data points: Balnton et al 2000 Madgwick et al. 2002 Zucca et al. 1997 Bimodal color distribution u-r color MBH-σ relation AGN luminosity function

10. high-z QSO Haring & Rix 2004 Marconi & Hunt 2003 The predicted MBH-M* relation z=0.1 z=4 local relation local relation data points: Evolutionary paths followed by BH with MBH(z=0)>1010 M data points: Maiolino et al. 07 Riechers et al. 08, 09 Walter et al. 04 Barth et al. 03 Dietrich & Hamann 04 Shields et al. 07 Riechers et al. 09 Lamastra et al. 2010 MNRAS

11. Selecting massive BHs at high z Contour plots: fraction of objects with a given Γ(z) Starformation from 0.01 (lightest) to 0.1 (darkest) BH accretion Γ >1 when we select MBH >109 M at z≥4 Galaxies formed in biased, high density regions undergo major merging events at high redshifts. At z ≲ 2.5 interaction-driven AGN feeding drops while quiescent star formation still builds up stellar mass bringing Γ→1 Lamastra et al. 2010 MNRAS

12. Selecting intermediate-mass objects at z=1-2 Contour plots: fraction of objects with a given Γ(z) from 0.01 (lightest) to 0.1 (darkest) Galaxies formed in less biased regions of the primordial density field: lower interaction rate at z≳4 The excess Γ>1 is less pronounced Observations by Merloni et al. 2010: log LX/erg s-1>44.5 Lamastra et al. 2010 MNRAS

13. local relation Selecting gas-rich, star forming galaxies at z=2-3 Contour plots: fraction of objects with a given Γ(z) from 0.01 (lightest) to 0.1 (darkest) datapoints: Alexander et al. 2008 Adopted selection critera consistent with those adopted by Alexander et al. 08 Gas Fraction ≥ 0.7(see Tacconi et al. 06, 08; Swinbank et al. 08)SFR ≥ 100M/yr Γ(z)<1 for galaxies which retained a large gas fraction at z=2-3 (galaxies originated from merging histories characterized by less prominent high-z interactions) Lamastra et al. 2010 MNRAS

14. 5% of the final mass 50% of the final mass 90% of the final mass Mass dependence of Γ(z) Lamastra et al. 2010 MNRAS Downsizing in the assembly of BH masses Massive local galaxies have formed preferentially through path passing above the local MBH-M* relation Marconi et al. 2004

15. Summary • Interaction-driven fueling of AGNs within Cosmological galaxy formation models yields: • Γ(z)>1 for massive galaxies at high redshift (i.e., when merging histories characteristic of biased, high-density regions of the primordial density field are selected) • Γ≃2 for luminous (Lbol≥1044.5 erg/s) QSO at z=1-2 • Γ≃4 for massive (MBH≥109 M) in QSOs at z≳4 • Γ(z)<1 for galaxies which retained a large gas fraction at z=2-3 (i.e., which did not convert the whole gas content into stars at high redshifts) • Γ≃(0.3-1) for SMG-like galaxies hosting active AGNs (LX≥1043 erg/s, large SFR and gas fraction ). These evolve to local galaxies with masses MBH < 109 M • At any given z, Γ(z) is predicted to increase with BH mass • Corresponds to a ‘’downsizing’’ in the assembly of BH masses • Measuring Γ(z) for an unbiased sample of AGN can provide crucial constraints on interaction-driven fueling scenarios for the growth of SMBHs in a cosmological context

19. NO AGN feedb AGN feedb In the absence of AGN feedback a sizeble fraction of large-mass galaxies has blue colors

20. The low redshift descendants of SMGs are predicted to have BH with MBH=108-109 M, in agreement with the independent finding of Alexander et al. 2008 based on the larger number density of SMGs compared to that of local galaxies hosting BH with MBH>109M