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Galaxies and AGNs Four decades ago, idea that accretion of matter onto a supermassive black hole (SMBH) >10^6 Msun powers luminous active galactic muclei (AGN), in particular quasi-stellar objects (QSO) Dynamical evidence that SMBH pervade the centers of most massive galaxies Challenge is now to understand the fueling and evolution of AGNs, and how they relate to host galaxies and their evolution Why not all relatively massive galaxies show AGN activity, while they harbor SBMH? - What is role of internal galactic structure and environment?
BH masses and their relation with Galaxy Bulge/Halo High resolution gas and stellar dynamical measurements of BHM: large central densities inferred within a small resolved radius - Our Galaxy 3-4 X 10^6 Msun Majority of measurements target ellipticals and a few early-type (Sa-Sbc) spirals, and probe BHM in the range 10^7-10^9. More challenging measurements in late-type spirals and dwarfs, and in Seyferts and LINERS (where the bright active nucleus hides the spectroscopic features needed for dynamical measurements) Tight correlation between mass of central BH and stellar velocity dispersion (mass) of the host galaxy’s bulge. This originally measured in local early-type (E/S0s) and a few Sb-Sbc quiescent galaxies, then found to hold also in AGN hosts and bright QSOs out to z~3 (Ferrarese et al. 2001, Shields et al. 2003). This translates into a relation between BH mass and mass of the dark matter halo within the LambdaCDM paradigm - This shows that both active and quiescent BHs bear a common relationship to the surrounding bulge of their host galaxy, over a wide range of cosmic epochs and BH masses (10^6-10^10).
The Angular Momentum Problem - Drive gas in by factor of 105 in R: Large-scale Circumnuclear Nuclear 50 kpc 1 kpc/few 100 pc 10s-0.1 pc - The Miracle: reduce specific L (angular momentum per unit mass) of gas by 5-6 orders of magnitude !!!! Location L = r x v in cm2 s-1 ---------------------------------------------------------------------------- At r=10kpc in a spiral disk 3e29 At r=200 pc in a spiral disk 4e27 At the last stable orbit of 2e24 M8 a BH of mass (108 x M8 ) -----------------------------------------------------------------------------
Driving gas from 10 kpc to 100 pc requires grav. torques from : • - non-axisymmetric stellar component : a stellar bar • - Interaction/merger torques by induced stellar bar and by companion • A pre-requisite for triggering high L starbursts/AGN ? • At lower R<200 pc, other mechanisms can drain angular momentum e.g., • nuclear bars, dynamical friction, magnetic torques, BH-binary, etc
Relative importance of different gas transport mechanisms vary acc to: • Mass accretion rates in different types of AGN (QSO, Seyfert, LINER,etc) • Quasars = 10-102 Mo yr--1 Seyferts = 10-3 - 10-2 Mo yr--1 • LINERS = 10-5- 10-4 Mo yr-- • Cosmic epoch (z~0 vs z>>1) and Hubble type ? Sd Scd Sc Sbc Sb Sab Sa ---------- ---------------------- > <--------------------------> Nucl. cluster - BH : if/when/how formed ? - SMBH—Bulge correlation No bulge. - Present-day secular evolution - z>>1: mergers build Bulges/BH? pseudo-bulges/compact disks? - z~0 : More ‘quiet’ drivers feed AGN
The accretion during the quasar era can account for the BH mass density observed in local early-type galaxies. Only a small fraction of present day BH density is in currently active Seyferts, mass accretion rates much lower. == No significant growth of BHs in the present epoch compared to the quasar era – thus local AGNs (Seyferts) may differ from luminous QSOs in nature of fueling, gas reservoir, nature of host galaxy
AGN vs Hubble type of Host Galaxy POSS (Ho et al. 1997) - Mag limited sample of 486 galaxies - B_T < 12.5 mag and dec >0 - Optical bar & Hubble type from RC3 AGN found mostly in luminous early type (E--Sbc) galaxies HII galaxies “prefer” less luminous late type (Sbc--later) • VC & V + RC3 .Study of 279 active spirals. No control sample(Moles et al 1995) • 80% = 233 = Sa-Sb 19%=17 later than Sb 0.7% =2 later than Sc • Amongst spiral galaxies, AGN tend to lie in early types (Sa-Sb)
Large-Scale Bars vs SBT or AGN E12MGS (Hunt & Malkan 1999) - 891 galaxies ; 116 Sy - Bar + optical type from RC3 - Nuclear type from NED : Sy LINER HII normal 0=S0/a 1~Sab 3~Sbc 5~Scd 6=Sd E12MGS Bar Fraction - "Normal" (quiescent) : 61-68 % - HII/Starburst : 82-85 % ;excess - AGN : 61-68 % ; no excess
Do bars fuel AGN? No/weak correlation between bars and Seyferts (Regan et al 1997; Knapen et al 2000; Laurikainen et al 2004) Angular Momemtum Problem: Bar only drive gas to 100 pc scale where L is 104 too high to feed BH. Nuclear mechanism needed Different lifetimes: Bars vs AGN Sy and QSO cases may be very different Seyferts: 10-2 Mo yr-1 over 108 yrs few x 106 Mo = few % of CN gas QSOs: 10-100 Mo yr-1 over 108 yrs 109-1010 Mo (Jogee 2004, AGN Physics on All Scales, Chapter 6)
Summary : Host Galaxy vs AGN , Starbursts • AGN found mostly in luminous early type (E--Sbc) galaxies • Large-scale bar fraction in starbursts (at least relatively luminous ones) is higher wrt normal galaxies (Hunt & Malkan 1999; Hawarden et al. 1986; Mazzarella & Balzano 1986). Correlation less clear for lower luminosity starburst(e.g., Ho et al. 1997) • Large-scale bar fraction in Seyferts is comparable to or slighlty higher than in normal galaxies (Mulchaey & Regan 1997; Hunt & Malkan 1999; Knapen et al 2000)
Why no strong correlation: Primary Bars vs AGN? • Specific Angular Momentum • Bars solve L problem half way : L down by 10-100, R from 10s kpc to 200 pc • Delay between bar-driven gas inflow on few 100 pc scale & onset of AGN • e.g., onset of nuclear gas transport mechanisms, dynamical evolution of dense cluster • Must have both (massive BH + gas) to show AGN. Favored in early type? • Can AGN fuelling destroy primary bar? • - Freq of outer rings and of (inner +outer) rings is 3-4 times higher in Sy (HM 99) • - Slight deficiency of strong bars in Seyferts (Shlosman et al. 2000) • BUT …………………. • Efficient ways other than bars to drive gas to 100 pc scale. e.g., major mergers
Starburst or AGN vs. Companions/Interactions/Merger • Correlation between starbursts and companions or interactions/mergers exist at high luminosity and extreme end (dM/dt >>1 Mo/yr) • e.g., VLIRGs and ULIRGs • Bright Arp galaxies , • Bright Hickson CG HII galaxies • Correlation between AGN activity and companions/interactions/mergers exist at high luminosity and extreme end (dM/dt >>1 Mo/yr) • e.g., Radio-loud (and quiet) QSOs , FRII radio galaxies • but conflicting results for lower lumnosity AGN • e.g., Sy, LINERS
Why correlation of (Interactions vs AGN or starbursts) only at high L end? • Not all speed, orientations, and impact parameters of interactions trigger strong gas inflows • Minor (1:10), intermediate mass ratio (1:4) interactions drive gas inflow by inducing large-scale bars....same limitations as bars . • reduce L by < 100 , and time delay between inflow and onset of AGN • Major mergers(Mihos & Hernquist 1996) • Early stage : as above • Final stage: Potential strongly varying. • Gas on interseccting orbits shocks and dissipates strong inflow. • ?? Do final stages of major merger buy us the extra 10 3 loss in L?? • Via shocks + sb-driven outflows+AGN outflow ?
Forming SMBH+Bulges in the Early Universe? • QSO detected at z> 6 or or t<1 Gyr (Fan et al. 2003) • SMBH form early since they “power” QSOs • In hierarchical models, bulges and SMBH both form during major mergers (+ feedback inhibiting further growth of BH) • Patches collapse when gravity • overcomes expansion . • Baryons radiate, collapse in a • disk, form stars. • Protogalaxies merge • Major merger of 2 disks forms Bulge/EG • - trigger starburst + sb-outflow • - can it form SMBH + AGN outflow ??? • - SMBH-Bulge correlation at z>6 ? • NB:Later gas infall disk around bulge -> Sa
Summary : Interplays: Environment/SF/Fueling/AGN • Mass of central BH correlates tightly with stellar velocity dispersion of bulge of host galaxy. This points to symbiotic evolution of BH and bulge • To fuel gas from 10s kpc to AGN scale, must reduce L by 5-6 orders of mag There is no universal fueling mechanism that operates efficiently on all scales • Gravitational torques via Large-scale bar and interactions : most efficient • mechanism from 10s kpc to 100s pc : help only half way in L • Large-scale bar fraction • in luminous starbursts is higher w.r.t normal galaxies • in Seyferts is comparable to normal galaxies • Correlation exist only at high L end (dM/dt >>1 Mo/yr) between • starbursts-interactions AGN-interactions • The low accretion rates required in local Seyferts and low luminosity AGNs can probably be provided by localized low energetic processes that impact only the few circumnuclear gas