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).

- 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

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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 )

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The Angular Momentum Problem

• 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:

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

• 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 ?

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/Starbursts and Their Hosts

AGN vs Hubble type of Host Galaxy

AGN found mostly in luminous early type (E--Sbc) galaxies

HII galaxies “prefer” less luminous late type (Sbc--later)

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

• 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 Bar Fraction - "Normal" (quiescent) : 61-68 %

- HII/Starburst : 82-85 % ;excess

- AGN : 61-68 % ; no excess

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

(Jogee 2004, AGN Physics on All Scales, Chapter 6)

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

Do bars fuel AGN?

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/AGN vs.

Companions/Interactions/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?

• 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

• 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)

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